template: move exp/template into template.

(Leave exp/template/html where it is for now.)

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/4899048

20 files changed, 4518 insertions, 0 deletions

diff --git a/src/pkg/template/Makefile b/src/pkg/template/Makefile
new file mode 100644
index 000000000..3ed3b0330
--- /dev/null
+++ b/src/pkg/template/Makefile
@@ -0,0 +1,15 @@
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../Make.inc
+
+TARG=template
+GOFILES=\
+	exec.go\
+	funcs.go\
+	helper.go\
+	parse.go\
+	set.go\
+
+include ../../Make.pkg
diff --git a/src/pkg/template/doc.go b/src/pkg/template/doc.go
new file mode 100644
index 000000000..f65946aed
--- /dev/null
+++ b/src/pkg/template/doc.go
@@ -0,0 +1,313 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package template implements data-driven templates for generating textual output
+such as HTML.
+
+Templates are executed by applying them to a data structure. Annotations in the
+template refer to elements of the data structure (typically a field of a struct
+or a key in a map) to control execution and derive values to be displayed.
+Execution of the template walks the structure and sets the cursor, represented
+by a period '.' and called "dot", to the value at the current location in the
+structure as execution proceeds.
+
+The input text for a template is UTF-8-encoded text in any format.
+"Actions"--data evaluations or control structures--are delimited by
+"{{" and "}}"; all text outside actions is copied to the output unchanged.
+Actions may not span newlines, although comments can.
+
+Once constructed, templates and template sets can be executed safely in
+parallel.
+
+Actions
+
+Here is the list of actions. "Arguments" and "pipelines" are evaluations of
+data, defined in detail below.
+
+*/
+//	{{/* a comment */}}
+//		A comment; discarded. May contain newlines.
+//		Comments do not nest.
+/*
+
+	{{pipeline}}
+		The default textual representation of the value of the pipeline
+		is copied to the output.
+
+	{{if pipeline}} T1 {{end}}
+		If the value of the pipeline is empty, no output is generated;
+		otherwise, T1 is executed.  The empty values are false, 0, any
+		nil pointer or interface value, and any array, slice, map, or
+		string of length zero.
+		Dot is unaffected.
+
+	{{if pipeline}} T1 {{else}} T0 {{end}}
+		If the value of the pipeline is empty, T0 is executed;
+		otherwise, T1 is executed.  Dot is unaffected.
+
+	{{range pipeline}} T1 {{end}}
+		The value of the pipeline must be an array, slice, or map. If
+		the value of the pipeline has length zero, nothing is output;
+		otherwise, dot is set to the successive elements of the array,
+		slice, or map and T1 is executed.
+
+	{{range pipeline}} T1 {{else}} T0 {{end}}
+		The value of the pipeline must be an array, slice, or map. If
+		the value of the pipeline has length zero, dot is unaffected and
+		T0 is executed; otherwise, dot is set to the successive elements
+		of the array, slice, or map and T1 is executed.
+
+	{{template "name"}}
+		The template with the specified name is executed with nil data.
+
+	{{template "name" pipeline}}
+		The template with the specified name is executed with dot set
+		to the value of the pipeline.
+
+	{{with pipeline}} T1 {{end}}
+		If the value of the pipeline is empty, no output is generated;
+		otherwise, dot is set to the value of the pipeline and T1 is
+		executed.
+
+	{{with pipeline}} T1 {{else}} T0 {{end}}
+		If the value of the pipeline is empty, dot is unaffected and T0
+		is executed; otherwise, dot is set to the value of the pipeline
+		and T1 is executed.
+
+Arguments
+
+An argument is a simple value, denoted by one of the following.
+
+	- A boolean, string, character, integer, floating-point, imaginary
+	  or complex constant in Go syntax. These behave like Go's untyped
+	  constants, although raw strings may not span newlines.
+	- The character '.' (period):
+		.
+	  The result is the value of dot.
+	- A variable name, which is a (possibly empty) alphanumeric string
+	  preceded by a dollar sign, such as
+		$piOver2
+	  or
+		$
+	  The result is the value of the variable.
+	  Variables are described below.
+	- The name of a field of the data, which must be a struct, preceded
+	  by a period, such as
+		.Field
+	  The result is the value of the field. Field invocations may be
+	  chained:
+	    .Field1.Field2
+	  Fields can also be evaluated on variables, including chaining:
+	    $x.Field1.Field2
+	- The name of a key of the data, which must be a map, preceded
+	  by a period, such as
+		.Key
+	  The result is the map element value indexed by the key.
+	  Key invocations may be chained and combined with fields to any
+	  depth:
+	    .Field1.Key1.Field2.Key2
+	  Although the key must be an alphanumeric identifier, unlike with
+	  field names they do not need to start with an upper case letter.
+	  Keys can also be evaluated on variables, including chaining:
+	    $x.key1.key2
+	- The name of a niladic method of the data, preceded by a period,
+	  such as
+		.Method
+	  The result is the value of invoking the method with dot as the
+	  receiver, dot.Method(). Such a method must have one return value (of
+	  any type) or two return values, the second of which is an os.Error.
+	  If it has two and the returned error is non-nil, execution terminates
+	  and an error is returned to the caller as the value of Execute.
+	  Method invocations may be chained and combined with fields and keys
+	  to any depth:
+	    .Field1.Key1.Method1.Field2.Key2.Method2
+	  Methods can also be evaluated on variables, including chaining:
+	    $x.Method1.Field
+	- The name of a niladic function, such as
+		fun
+	  The result is the value of invoking the function, fun(). The return
+	  types and values behave as in methods. Functions and function
+	  names are described below.
+
+Arguments may evaluate to any type; if they are pointers the implementation
+automatically indirects to the base type when required.
+
+A pipeline is a possibly chained sequence of "commands". A command is a simple
+value (argument) or a function or method call, possibly with multiple arguments:
+
+	Argument
+		The result is the value of evaluating the argument.
+	.Method [Argument...]
+		The method can be alone or the last element of a chain but,
+		unlike methods in the middle of a chain, it can take arguments.
+		The result is the value of calling the method with the
+		arguments:
+			dot.Method(Argument1, etc.)
+	functionName [Argument...]
+		The result is the value of calling the function associated
+		with the name:
+			function(Argument1, etc.)
+		Functions and function names are described below.
+
+Pipelines
+
+A pipeline may be "chained" by separating a sequence of commands with pipeline
+characters '|'. In a chained pipeline, the result of the each command is
+passed as the last argument of the following command. The output of the final
+command in the pipeline is the value of the pipeline.
+
+The output of a command will be either one value or two values, the second of
+which has type os.Error. If that second value is present and evaluates to
+non-nil, execution terminates and the error is returned to the caller of
+Execute.
+
+Variables
+
+A pipeline inside an action may initialize a variable to capture the result.
+The initialization has syntax
+
+	$variable := pipeline
+
+where $variable is the name of the variable. An action that declares a
+variable produces no output.
+
+If a "range" action initializes a variable, the variable is set to the
+successive elements of the iteration.  Also, a "range" may declare two
+variables, separated by a comma:
+
+	$index, $element := pipeline
+
+in which case $index and $element are set to the successive values of the
+array/slice index or map key and element, respectively.  Note that if there is
+only one variable, it is assigned the element; this is opposite to the
+convention in Go range clauses.
+
+A variable's scope extends to the "end" action of the control structure ("if",
+"with", or "range") in which it is declared, or to the end of the template if
+there is no such control structure.  A template invocation does not inherit
+variables from the point of its invocation.
+
+When execution begins, $ is set to the data argument passed to Execute, that is,
+to the starting value of dot.
+
+Examples
+
+Here are some example one-line templates demonstrating pipelines and variables.
+All produce the quoted word "output":
+
+	{{"\"output\""}}
+		A string constant.
+	{{`"output"`}}
+		A raw string constant.
+	{{printf "%q" "output"}}
+		A function call.
+	{{"output" | printf "%q"}}
+		A function call whose final argument comes from the previous
+		command.
+	{{"put" | printf "%s%s" "out" | printf "%q"}}
+		A more elaborate call.
+	{{"output" | printf "%s" | printf "%q"}}
+		A longer chain.
+	{{with "output"}}{{printf "%q" .}}{{end}}
+		A with action using dot.
+	{{with $x := "output" | printf "%q"}}{{$x}}{{end}}
+		A with action that creates and uses a variable.
+	{{with $x := "output"}}{{printf "%q" $x}}{{end}}
+		A with action that uses the variable in another action.
+	{{with $x := "output"}}{{$x | printf "%q"}}{{end}}
+		The same, but pipelined.
+
+Functions
+
+During execution functions are found in three function maps: first in the
+template, then in the "template set" (described below), and finally in the
+global function map. By default, no functions are defined in the template or
+the set but the Funcs methods can be used to add them.
+
+Predefined global functions are named as follows.
+
+	and
+		Returns the boolean AND of its arguments by returning the
+		first empty argument or the last argument, that is,
+		"and x y" behaves as "if x then y else x". All the
+		arguments are evaluated.
+	html
+		Returns the escaped HTML equivalent of the textual
+		representation of its arguments.
+	index
+		Returns the result of indexing its first argument by the
+		following arguments. Thus "index x 1 2 3" is, in Go syntax,
+		x[1][2][3]. Each indexed item must be a map, slice, or array.
+	js
+		Returns the escaped JavaScript equivalent of the textual
+		representation of its arguments.
+	len
+		Returns the integer length of its argument.
+	not
+		Returns the boolean negation of its single argument.
+	or
+		Returns the boolean OR of its arguments by returning the
+		first non-empty argument or the last argument, that is,
+		"or x y" behaves as "if x then x else y". All the
+		arguments are evaluated.
+	print
+		An alias for fmt.Sprint
+	printf
+		An alias for fmt.Sprintf
+	println
+		An alias for fmt.Sprintln
+	urlquery
+		Returns the escaped value of the textual representation of
+		its arguments in a form suitable for embedding in a URL query.
+
+The boolean functions take any zero value to be false and a non-zero value to
+be true.
+
+Template sets
+
+Each template is named by a string specified when it is created.  A template may
+use a template invocation to instantiate another template directly or by its
+name; see the explanation of the template action above. The name is looked up
+in the template set associated with the template.
+
+If no template invocation actions occur in the template, the issue of template
+sets can be ignored.  If it does contain invocations, though, the template
+containing the invocations must be part of a template set in which to look up
+the names.
+
+There are two ways to construct template sets.
+
+The first is to use a Set's Parse method to create a set of named templates from
+a single input defining multiple templates.  The syntax of the definitions is to
+surround each template declaration with a define and end action.
+
+The define action names the template being created by providing a string
+constant. Here is a simple example of input to Set.Parse:
+
+	`{{define "T1"}} definition of template T1 {{end}}
+	{{define "T2"}} definition of template T2 {{end}}
+	{{define "T3"}} {{template "T1"}} {{template "T2"}} {{end}}`
+
+This defines two templates, T1 and T2, and a third T3 that invokes the other two
+when it is executed.
+
+The second way to build a template set is to use Set's Add method to add a
+parsed template to a set.  A template may be bound at most one set.  If it's
+necessary to have a template in multiple sets, the template definition must be
+parsed multiple times to create distinct *Template values.
+
+Set.Parse may be called multiple times on different inputs to construct the set.
+Two sets may therefore be constructed with a common base set of templates plus,
+through a second Parse call each, specializations for some elements.
+
+A template may be executed directly or through Set.Execute, which executes a
+named template from the set.  To invoke our example above, we might write,
+
+	err := set.Execute(os.Stdout, "T3", "no data needed")
+	if err != nil {
+		log.Fatalf("execution failed: %s", err)
+	}
+*/
+package template
diff --git a/src/pkg/template/exec.go b/src/pkg/template/exec.go
new file mode 100644
index 000000000..eaa57ae81
--- /dev/null
+++ b/src/pkg/template/exec.go
@@ -0,0 +1,655 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"reflect"
+	"runtime"
+	"strings"
+	"template/parse"
+)
+
+// state represents the state of an execution. It's not part of the
+// template so that multiple executions of the same template
+// can execute in parallel.
+type state struct {
+	tmpl *Template
+	wr   io.Writer
+	line int        // line number for errors
+	vars []variable // push-down stack of variable values.
+}
+
+// variable holds the dynamic value of a variable such as $, $x etc.
+type variable struct {
+	name  string
+	value reflect.Value
+}
+
+// push pushes a new variable on the stack.
+func (s *state) push(name string, value reflect.Value) {
+	s.vars = append(s.vars, variable{name, value})
+}
+
+// mark returns the length of the variable stack.
+func (s *state) mark() int {
+	return len(s.vars)
+}
+
+// pop pops the variable stack up to the mark.
+func (s *state) pop(mark int) {
+	s.vars = s.vars[0:mark]
+}
+
+// setVar overwrites the top-nth variable on the stack. Used by range iterations.
+func (s *state) setVar(n int, value reflect.Value) {
+	s.vars[len(s.vars)-n].value = value
+}
+
+// varValue returns the value of the named variable.
+func (s *state) varValue(name string) reflect.Value {
+	for i := s.mark() - 1; i >= 0; i-- {
+		if s.vars[i].name == name {
+			return s.vars[i].value
+		}
+	}
+	s.errorf("undefined variable: %s", name)
+	return zero
+}
+
+var zero reflect.Value
+
+// errorf formats the error and terminates processing.
+func (s *state) errorf(format string, args ...interface{}) {
+	format = fmt.Sprintf("template: %s:%d: %s", s.tmpl.Name(), s.line, format)
+	panic(fmt.Errorf(format, args...))
+}
+
+// error terminates processing.
+func (s *state) error(err os.Error) {
+	s.errorf("%s", err)
+}
+
+// errRecover is the handler that turns panics into returns from the top
+// level of Parse.
+func errRecover(errp *os.Error) {
+	e := recover()
+	if e != nil {
+		if _, ok := e.(runtime.Error); ok {
+			panic(e)
+		}
+		*errp = e.(os.Error)
+	}
+}
+
+// Execute applies a parsed template to the specified data object,
+// writing the output to wr.
+func (t *Template) Execute(wr io.Writer, data interface{}) (err os.Error) {
+	defer errRecover(&err)
+	value := reflect.ValueOf(data)
+	state := &state{
+		tmpl: t,
+		wr:   wr,
+		line: 1,
+		vars: []variable{{"$", value}},
+	}
+	if t.Root == nil {
+		state.errorf("must be parsed before execution")
+	}
+	state.walk(value, t.Root)
+	return
+}
+
+// Walk functions step through the major pieces of the template structure,
+// generating output as they go.
+func (s *state) walk(dot reflect.Value, n parse.Node) {
+	switch n := n.(type) {
+	case *parse.ActionNode:
+		s.line = n.Line
+		// Do not pop variables so they persist until next end.
+		// Also, if the action declares variables, don't print the result.
+		val := s.evalPipeline(dot, n.Pipe)
+		if len(n.Pipe.Decl) == 0 {
+			s.printValue(n, val)
+		}
+	case *parse.IfNode:
+		s.line = n.Line
+		s.walkIfOrWith(parse.NodeIf, dot, n.Pipe, n.List, n.ElseList)
+	case *parse.ListNode:
+		for _, node := range n.Nodes {
+			s.walk(dot, node)
+		}
+	case *parse.RangeNode:
+		s.line = n.Line
+		s.walkRange(dot, n)
+	case *parse.TemplateNode:
+		s.line = n.Line
+		s.walkTemplate(dot, n)
+	case *parse.TextNode:
+		if _, err := s.wr.Write(n.Text); err != nil {
+			s.error(err)
+		}
+	case *parse.WithNode:
+		s.line = n.Line
+		s.walkIfOrWith(parse.NodeWith, dot, n.Pipe, n.List, n.ElseList)
+	default:
+		s.errorf("unknown node: %s", n)
+	}
+}
+
+// walkIfOrWith walks an 'if' or 'with' node. The two control structures
+// are identical in behavior except that 'with' sets dot.
+func (s *state) walkIfOrWith(typ parse.NodeType, dot reflect.Value, pipe *parse.PipeNode, list, elseList *parse.ListNode) {
+	defer s.pop(s.mark())
+	val := s.evalPipeline(dot, pipe)
+	truth, ok := isTrue(val)
+	if !ok {
+		s.errorf("if/with can't use %v", val)
+	}
+	if truth {
+		if typ == parse.NodeWith {
+			s.walk(val, list)
+		} else {
+			s.walk(dot, list)
+		}
+	} else if elseList != nil {
+		s.walk(dot, elseList)
+	}
+}
+
+// isTrue returns whether the value is 'true', in the sense of not the zero of its type,
+// and whether the value has a meaningful truth value.
+func isTrue(val reflect.Value) (truth, ok bool) {
+	if !val.IsValid() {
+		// Something like var x interface{}, never set. It's a form of nil.
+		return false, true
+	}
+	switch val.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		truth = val.Len() > 0
+	case reflect.Bool:
+		truth = val.Bool()
+	case reflect.Complex64, reflect.Complex128:
+		truth = val.Complex() != 0
+	case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
+		truth = !val.IsNil()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		truth = val.Int() != 0
+	case reflect.Float32, reflect.Float64:
+		truth = val.Float() != 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		truth = val.Uint() != 0
+	case reflect.Struct:
+		truth = true // Struct values are always true.
+	default:
+		return
+	}
+	return truth, true
+}
+
+func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
+	defer s.pop(s.mark())
+	val, _ := indirect(s.evalPipeline(dot, r.Pipe))
+	// mark top of stack before any variables in the body are pushed.
+	mark := s.mark()
+	switch val.Kind() {
+	case reflect.Array, reflect.Slice:
+		if val.Len() == 0 {
+			break
+		}
+		for i := 0; i < val.Len(); i++ {
+			elem := val.Index(i)
+			// Set top var (lexically the second if there are two) to the element.
+			if len(r.Pipe.Decl) > 0 {
+				s.setVar(1, elem)
+			}
+			// Set next var (lexically the first if there are two) to the index.
+			if len(r.Pipe.Decl) > 1 {
+				s.setVar(2, reflect.ValueOf(i))
+			}
+			s.walk(elem, r.List)
+			s.pop(mark)
+		}
+		return
+	case reflect.Map:
+		if val.Len() == 0 {
+			break
+		}
+		for _, key := range val.MapKeys() {
+			elem := val.MapIndex(key)
+			// Set top var (lexically the second if there are two) to the element.
+			if len(r.Pipe.Decl) > 0 {
+				s.setVar(1, elem)
+			}
+			// Set next var (lexically the first if there are two) to the key.
+			if len(r.Pipe.Decl) > 1 {
+				s.setVar(2, key)
+			}
+			s.walk(elem, r.List)
+			s.pop(mark)
+		}
+		return
+	case reflect.Invalid:
+		break // An invalid value is likely a nil map, etc. and acts like an empty map.
+	default:
+		s.errorf("range can't iterate over %v", val)
+	}
+	if r.ElseList != nil {
+		s.walk(dot, r.ElseList)
+	}
+}
+
+func (s *state) walkTemplate(dot reflect.Value, t *parse.TemplateNode) {
+	set := s.tmpl.set
+	if set == nil {
+		s.errorf("no set defined in which to invoke template named %q", t.Name)
+	}
+	tmpl := set.tmpl[t.Name]
+	if tmpl == nil {
+		s.errorf("template %q not in set", t.Name)
+	}
+	// Variables declared by the pipeline persist.
+	dot = s.evalPipeline(dot, t.Pipe)
+	newState := *s
+	newState.tmpl = tmpl
+	// No dynamic scoping: template invocations inherit no variables.
+	newState.vars = []variable{{"$", dot}}
+	newState.walk(dot, tmpl.Root)
+}
+
+// Eval functions evaluate pipelines, commands, and their elements and extract
+// values from the data structure by examining fields, calling methods, and so on.
+// The printing of those values happens only through walk functions.
+
+// evalPipeline returns the value acquired by evaluating a pipeline. If the
+// pipeline has a variable declaration, the variable will be pushed on the
+// stack. Callers should therefore pop the stack after they are finished
+// executing commands depending on the pipeline value.
+func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value reflect.Value) {
+	if pipe == nil {
+		return
+	}
+	for _, cmd := range pipe.Cmds {
+		value = s.evalCommand(dot, cmd, value) // previous value is this one's final arg.
+		// If the object has type interface{}, dig down one level to the thing inside.
+		if value.Kind() == reflect.Interface && value.Type().NumMethod() == 0 {
+			value = reflect.ValueOf(value.Interface()) // lovely!
+		}
+	}
+	for _, variable := range pipe.Decl {
+		s.push(variable.Ident[0], value)
+	}
+	return value
+}
+
+func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
+	if len(args) > 1 || final.IsValid() {
+		s.errorf("can't give argument to non-function %s", args[0])
+	}
+}
+
+func (s *state) evalCommand(dot reflect.Value, cmd *parse.CommandNode, final reflect.Value) reflect.Value {
+	firstWord := cmd.Args[0]
+	switch n := firstWord.(type) {
+	case *parse.FieldNode:
+		return s.evalFieldNode(dot, n, cmd.Args, final)
+	case *parse.IdentifierNode:
+		// Must be a function.
+		return s.evalFunction(dot, n.Ident, cmd.Args, final)
+	case *parse.VariableNode:
+		return s.evalVariableNode(dot, n, cmd.Args, final)
+	}
+	s.notAFunction(cmd.Args, final)
+	switch word := firstWord.(type) {
+	case *parse.BoolNode:
+		return reflect.ValueOf(word.True)
+	case *parse.DotNode:
+		return dot
+	case *parse.NumberNode:
+		return s.idealConstant(word)
+	case *parse.StringNode:
+		return reflect.ValueOf(word.Text)
+	}
+	s.errorf("can't evaluate command %q", firstWord)
+	panic("not reached")
+}
+
+// idealConstant is called to return the value of a number in a context where
+// we don't know the type. In that case, the syntax of the number tells us
+// its type, and we use Go rules to resolve.  Note there is no such thing as
+// a uint ideal constant in this situation - the value must be of int type.
+func (s *state) idealConstant(constant *parse.NumberNode) reflect.Value {
+	// These are ideal constants but we don't know the type
+	// and we have no context.  (If it was a method argument,
+	// we'd know what we need.) The syntax guides us to some extent.
+	switch {
+	case constant.IsComplex:
+		return reflect.ValueOf(constant.Complex128) // incontrovertible.
+	case constant.IsFloat && strings.IndexAny(constant.Text, ".eE") >= 0:
+		return reflect.ValueOf(constant.Float64)
+	case constant.IsInt:
+		n := int(constant.Int64)
+		if int64(n) != constant.Int64 {
+			s.errorf("%s overflows int", constant.Text)
+		}
+		return reflect.ValueOf(n)
+	case constant.IsUint:
+		s.errorf("%s overflows int", constant.Text)
+	}
+	return zero
+}
+
+func (s *state) evalFieldNode(dot reflect.Value, field *parse.FieldNode, args []parse.Node, final reflect.Value) reflect.Value {
+	return s.evalFieldChain(dot, dot, field.Ident, args, final)
+}
+
+func (s *state) evalVariableNode(dot reflect.Value, v *parse.VariableNode, args []parse.Node, final reflect.Value) reflect.Value {
+	// $x.Field has $x as the first ident, Field as the second. Eval the var, then the fields.
+	value := s.varValue(v.Ident[0])
+	if len(v.Ident) == 1 {
+		return value
+	}
+	return s.evalFieldChain(dot, value, v.Ident[1:], args, final)
+}
+
+// evalFieldChain evaluates .X.Y.Z possibly followed by arguments.
+// dot is the environment in which to evaluate arguments, while
+// receiver is the value being walked along the chain.
+func (s *state) evalFieldChain(dot, receiver reflect.Value, ident []string, args []parse.Node, final reflect.Value) reflect.Value {
+	n := len(ident)
+	for i := 0; i < n-1; i++ {
+		receiver = s.evalField(dot, ident[i], nil, zero, receiver)
+	}
+	// Now if it's a method, it gets the arguments.
+	return s.evalField(dot, ident[n-1], args, final, receiver)
+}
+
+func (s *state) evalFunction(dot reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
+	function, ok := findFunction(name, s.tmpl, s.tmpl.set)
+	if !ok {
+		s.errorf("%q is not a defined function", name)
+	}
+	return s.evalCall(dot, function, name, args, final)
+}
+
+// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
+// The 'final' argument represents the return value from the preceding
+// value of the pipeline, if any.
+func (s *state) evalField(dot reflect.Value, fieldName string, args []parse.Node, final, receiver reflect.Value) reflect.Value {
+	if !receiver.IsValid() {
+		return zero
+	}
+	typ := receiver.Type()
+	receiver, _ = indirect(receiver)
+	// Unless it's an interface, need to get to a value of type *T to guarantee
+	// we see all methods of T and *T.
+	ptr := receiver
+	if ptr.Kind() != reflect.Interface && ptr.CanAddr() {
+		ptr = ptr.Addr()
+	}
+	if method, ok := methodByName(ptr, fieldName); ok {
+		return s.evalCall(dot, method, fieldName, args, final)
+	}
+	hasArgs := len(args) > 1 || final.IsValid()
+	// It's not a method; is it a field of a struct?
+	receiver, isNil := indirect(receiver)
+	if receiver.Kind() == reflect.Struct {
+		tField, ok := receiver.Type().FieldByName(fieldName)
+		if ok {
+			field := receiver.FieldByIndex(tField.Index)
+			if hasArgs {
+				s.errorf("%s is not a method but has arguments", fieldName)
+			}
+			if tField.PkgPath == "" { // field is exported
+				return field
+			}
+		}
+	}
+	// If it's a map, attempt to use the field name as a key.
+	if receiver.Kind() == reflect.Map {
+		nameVal := reflect.ValueOf(fieldName)
+		if nameVal.Type().AssignableTo(receiver.Type().Key()) {
+			if hasArgs {
+				s.errorf("%s is not a method but has arguments", fieldName)
+			}
+			return receiver.MapIndex(nameVal)
+		}
+	}
+	if isNil {
+		s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+	}
+	s.errorf("can't evaluate field %s in type %s", fieldName, typ)
+	panic("not reached")
+}
+
+// TODO: delete when reflect's own MethodByName is released.
+func methodByName(receiver reflect.Value, name string) (reflect.Value, bool) {
+	typ := receiver.Type()
+	for i := 0; i < typ.NumMethod(); i++ {
+		if typ.Method(i).Name == name {
+			return receiver.Method(i), true // This value includes the receiver.
+		}
+	}
+	return zero, false
+}
+
+var (
+	osErrorType     = reflect.TypeOf((*os.Error)(nil)).Elem()
+	fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
+)
+
+// evalCall executes a function or method call. If it's a method, fun already has the receiver bound, so
+// it looks just like a function call.  The arg list, if non-nil, includes (in the manner of the shell), arg[0]
+// as the function itself.
+func (s *state) evalCall(dot, fun reflect.Value, name string, args []parse.Node, final reflect.Value) reflect.Value {
+	if args != nil {
+		args = args[1:] // Zeroth arg is function name/node; not passed to function.
+	}
+	typ := fun.Type()
+	numIn := len(args)
+	if final.IsValid() {
+		numIn++
+	}
+	numFixed := len(args)
+	if typ.IsVariadic() {
+		numFixed = typ.NumIn() - 1 // last arg is the variadic one.
+		if numIn < numFixed {
+			s.errorf("wrong number of args for %s: want at least %d got %d", name, typ.NumIn()-1, len(args))
+		}
+	} else if numIn < typ.NumIn()-1 || !typ.IsVariadic() && numIn != typ.NumIn() {
+		s.errorf("wrong number of args for %s: want %d got %d", name, typ.NumIn(), len(args))
+	}
+	if !goodFunc(typ) {
+		s.errorf("can't handle multiple results from method/function %q", name)
+	}
+	// Build the arg list.
+	argv := make([]reflect.Value, numIn)
+	// Args must be evaluated. Fixed args first.
+	i := 0
+	for ; i < numFixed; i++ {
+		argv[i] = s.evalArg(dot, typ.In(i), args[i])
+	}
+	// Now the ... args.
+	if typ.IsVariadic() {
+		argType := typ.In(typ.NumIn() - 1).Elem() // Argument is a slice.
+		for ; i < len(args); i++ {
+			argv[i] = s.evalArg(dot, argType, args[i])
+		}
+	}
+	// Add final value if necessary.
+	if final.IsValid() {
+		argv[i] = final
+	}
+	result := fun.Call(argv)
+	// If we have an os.Error that is not nil, stop execution and return that error to the caller.
+	if len(result) == 2 && !result[1].IsNil() {
+		s.errorf("error calling %s: %s", name, result[1].Interface().(os.Error))
+	}
+	return result[0]
+}
+
+// validateType guarantees that the value is valid and assignable to the type.
+func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
+	if !value.IsValid() {
+		s.errorf("invalid value; expected %s", typ)
+	}
+	if !value.Type().AssignableTo(typ) {
+		s.errorf("wrong type for value; expected %s; got %s", typ, value.Type())
+	}
+	return value
+}
+
+func (s *state) evalArg(dot reflect.Value, typ reflect.Type, n parse.Node) reflect.Value {
+	switch arg := n.(type) {
+	case *parse.DotNode:
+		return s.validateType(dot, typ)
+	case *parse.FieldNode:
+		return s.validateType(s.evalFieldNode(dot, arg, []parse.Node{n}, zero), typ)
+	case *parse.VariableNode:
+		return s.validateType(s.evalVariableNode(dot, arg, nil, zero), typ)
+	}
+	switch typ.Kind() {
+	case reflect.Bool:
+		return s.evalBool(typ, n)
+	case reflect.Complex64, reflect.Complex128:
+		return s.evalComplex(typ, n)
+	case reflect.Float32, reflect.Float64:
+		return s.evalFloat(typ, n)
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return s.evalInteger(typ, n)
+	case reflect.Interface:
+		if typ.NumMethod() == 0 {
+			return s.evalEmptyInterface(dot, n)
+		}
+	case reflect.String:
+		return s.evalString(typ, n)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return s.evalUnsignedInteger(typ, n)
+	}
+	s.errorf("can't handle %s for arg of type %s", n, typ)
+	panic("not reached")
+}
+
+func (s *state) evalBool(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.BoolNode); ok {
+		value := reflect.New(typ).Elem()
+		value.SetBool(n.True)
+		return value
+	}
+	s.errorf("expected bool; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalString(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.StringNode); ok {
+		value := reflect.New(typ).Elem()
+		value.SetString(n.Text)
+		return value
+	}
+	s.errorf("expected string; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalInteger(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.NumberNode); ok && n.IsInt {
+		value := reflect.New(typ).Elem()
+		value.SetInt(n.Int64)
+		return value
+	}
+	s.errorf("expected integer; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalUnsignedInteger(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.NumberNode); ok && n.IsUint {
+		value := reflect.New(typ).Elem()
+		value.SetUint(n.Uint64)
+		return value
+	}
+	s.errorf("expected unsigned integer; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalFloat(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.NumberNode); ok && n.IsFloat {
+		value := reflect.New(typ).Elem()
+		value.SetFloat(n.Float64)
+		return value
+	}
+	s.errorf("expected float; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalComplex(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.NumberNode); ok && n.IsComplex {
+		value := reflect.New(typ).Elem()
+		value.SetComplex(n.Complex128)
+		return value
+	}
+	s.errorf("expected complex; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalEmptyInterface(dot reflect.Value, n parse.Node) reflect.Value {
+	switch n := n.(type) {
+	case *parse.BoolNode:
+		return reflect.ValueOf(n.True)
+	case *parse.DotNode:
+		return dot
+	case *parse.FieldNode:
+		return s.evalFieldNode(dot, n, nil, zero)
+	case *parse.IdentifierNode:
+		return s.evalFunction(dot, n.Ident, nil, zero)
+	case *parse.NumberNode:
+		return s.idealConstant(n)
+	case *parse.StringNode:
+		return reflect.ValueOf(n.Text)
+	case *parse.VariableNode:
+		return s.evalVariableNode(dot, n, nil, zero)
+	}
+	s.errorf("can't handle assignment of %s to empty interface argument", n)
+	panic("not reached")
+}
+
+// indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
+// We indirect through pointers and empty interfaces (only) because
+// non-empty interfaces have methods we might need.
+func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
+	for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
+		if v.IsNil() {
+			return v, true
+		}
+		if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
+			break
+		}
+	}
+	return v, false
+}
+
+// printValue writes the textual representation of the value to the output of
+// the template.
+func (s *state) printValue(n parse.Node, v reflect.Value) {
+	if v.Kind() == reflect.Ptr {
+		v, _ = indirect(v) // fmt.Fprint handles nil.
+	}
+	if !v.IsValid() {
+		fmt.Fprint(s.wr, "<no value>")
+		return
+	}
+
+	if !v.Type().Implements(fmtStringerType) {
+		if v.CanAddr() && reflect.PtrTo(v.Type()).Implements(fmtStringerType) {
+			v = v.Addr()
+		} else {
+			switch v.Kind() {
+			case reflect.Chan, reflect.Func:
+				s.errorf("can't print %s of type %s", n, v.Type())
+			}
+		}
+	}
+	fmt.Fprint(s.wr, v.Interface())
+}
diff --git a/src/pkg/template/exec_test.go b/src/pkg/template/exec_test.go
new file mode 100644
index 000000000..82f56e13c
--- /dev/null
+++ b/src/pkg/template/exec_test.go
@@ -0,0 +1,580 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"os"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+)
+
+var debug = flag.Bool("debug", false, "show the errors produced by the tests")
+
+// T has lots of interesting pieces to use to test execution.
+type T struct {
+	// Basics
+	True        bool
+	I           int
+	U16         uint16
+	X           string
+	FloatZero   float64
+	ComplexZero float64
+	// Nested structs.
+	U *U
+	// Struct with String method.
+	V0     V
+	V1, V2 *V
+	// Slices
+	SI      []int
+	SIEmpty []int
+	SB      []bool
+	// Maps
+	MSI      map[string]int
+	MSIone   map[string]int // one element, for deterministic output
+	MSIEmpty map[string]int
+	MXI      map[interface{}]int
+	MII      map[int]int
+	SMSI     []map[string]int
+	// Empty interfaces; used to see if we can dig inside one.
+	Empty0 interface{} // nil
+	Empty1 interface{}
+	Empty2 interface{}
+	Empty3 interface{}
+	Empty4 interface{}
+	// Non-empty interface.
+	NonEmptyInterface I
+	// Stringer.
+	Str fmt.Stringer
+	// Pointers
+	PI  *int
+	PSI *[]int
+	NIL *int
+	// Template to test evaluation of templates.
+	Tmpl *Template
+}
+
+type U struct {
+	V string
+}
+
+type V struct {
+	j int
+}
+
+func (v *V) String() string {
+	if v == nil {
+		return "nilV"
+	}
+	return fmt.Sprintf("<%d>", v.j)
+}
+
+var tVal = &T{
+	True:   true,
+	I:      17,
+	U16:    16,
+	X:      "x",
+	U:      &U{"v"},
+	V0:     V{6666},
+	V1:     &V{7777}, // leave V2 as nil
+	SI:     []int{3, 4, 5},
+	SB:     []bool{true, false},
+	MSI:    map[string]int{"one": 1, "two": 2, "three": 3},
+	MSIone: map[string]int{"one": 1},
+	MXI:    map[interface{}]int{"one": 1},
+	MII:    map[int]int{1: 1},
+	SMSI: []map[string]int{
+		{"one": 1, "two": 2},
+		{"eleven": 11, "twelve": 12},
+	},
+	Empty1:            3,
+	Empty2:            "empty2",
+	Empty3:            []int{7, 8},
+	Empty4:            &U{"UinEmpty"},
+	NonEmptyInterface: new(T),
+	Str:               os.NewError("foozle"),
+	PI:                newInt(23),
+	PSI:               newIntSlice(21, 22, 23),
+	Tmpl:              Must(New("x").Parse("test template")), // "x" is the value of .X
+}
+
+// A non-empty interface.
+type I interface {
+	Method0() string
+}
+
+var iVal I = tVal
+
+// Helpers for creation.
+func newInt(n int) *int {
+	p := new(int)
+	*p = n
+	return p
+}
+
+func newIntSlice(n ...int) *[]int {
+	p := new([]int)
+	*p = make([]int, len(n))
+	copy(*p, n)
+	return p
+}
+
+// Simple methods with and without arguments.
+func (t *T) Method0() string {
+	return "M0"
+}
+
+func (t *T) Method1(a int) int {
+	return a
+}
+
+func (t *T) Method2(a uint16, b string) string {
+	return fmt.Sprintf("Method2: %d %s", a, b)
+}
+
+func (t *T) MAdd(a int, b []int) []int {
+	v := make([]int, len(b))
+	for i, x := range b {
+		v[i] = x + a
+	}
+	return v
+}
+
+// MSort is used to sort map keys for stable output. (Nice trick!)
+func (t *T) MSort(m map[string]int) []string {
+	keys := make([]string, len(m))
+	i := 0
+	for k := range m {
+		keys[i] = k
+		i++
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+// EPERM returns a value and an os.Error according to its argument.
+func (t *T) EPERM(error bool) (bool, os.Error) {
+	if error {
+		return true, os.EPERM
+	}
+	return false, nil
+}
+
+// A few methods to test chaining.
+func (t *T) GetU() *U {
+	return t.U
+}
+
+func (u *U) TrueFalse(b bool) string {
+	if b {
+		return "true"
+	}
+	return ""
+}
+
+func typeOf(arg interface{}) string {
+	return fmt.Sprintf("%T", arg)
+}
+
+type execTest struct {
+	name   string
+	input  string
+	output string
+	data   interface{}
+	ok     bool
+}
+
+// bigInt and bigUint are hex string representing numbers either side
+// of the max int boundary.
+// We do it this way so the test doesn't depend on ints being 32 bits.
+var (
+	bigInt  = fmt.Sprintf("0x%x", int(1<<uint(reflect.TypeOf(0).Bits()-1)-1))
+	bigUint = fmt.Sprintf("0x%x", uint(1<<uint(reflect.TypeOf(0).Bits()-1)))
+)
+
+var execTests = []execTest{
+	// Trivial cases.
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+
+	// Ideal constants.
+	{"ideal int", "{{typeOf 3}}", "int", 0, true},
+	{"ideal float", "{{typeOf 1.0}}", "float64", 0, true},
+	{"ideal exp float", "{{typeOf 1e1}}", "float64", 0, true},
+	{"ideal complex", "{{typeOf 1i}}", "complex128", 0, true},
+	{"ideal int", "{{typeOf " + bigInt + "}}", "int", 0, true},
+	{"ideal too big", "{{typeOf " + bigUint + "}}", "", 0, false},
+
+	// Fields of structs.
+	{".X", "-{{.X}}-", "-x-", tVal, true},
+	{".U.V", "-{{.U.V}}-", "-v-", tVal, true},
+
+	// Fields on maps.
+	{"map .one", "{{.MSI.one}}", "1", tVal, true},
+	{"map .two", "{{.MSI.two}}", "2", tVal, true},
+	{"map .NO", "{{.MSI.NO}}", "<no value>", tVal, true},
+	{"map .one interface", "{{.MXI.one}}", "1", tVal, true},
+	{"map .WRONG args", "{{.MSI.one 1}}", "", tVal, false},
+	{"map .WRONG type", "{{.MII.one}}", "", tVal, false},
+
+	// Dots of all kinds to test basic evaluation.
+	{"dot int", "<{{.}}>", "<13>", 13, true},
+	{"dot uint", "<{{.}}>", "<14>", uint(14), true},
+	{"dot float", "<{{.}}>", "<15.1>", 15.1, true},
+	{"dot bool", "<{{.}}>", "<true>", true, true},
+	{"dot complex", "<{{.}}>", "<(16.2-17i)>", 16.2 - 17i, true},
+	{"dot string", "<{{.}}>", "<hello>", "hello", true},
+	{"dot slice", "<{{.}}>", "<[-1 -2 -3]>", []int{-1, -2, -3}, true},
+	{"dot map", "<{{.}}>", "<map[two:22 one:11]>", map[string]int{"one": 11, "two": 22}, true},
+	{"dot struct", "<{{.}}>", "<{7 seven}>", struct {
+		a int
+		b string
+	}{7, "seven"}, true},
+
+	// Variables.
+	{"$ int", "{{$}}", "123", 123, true},
+	{"$.I", "{{$.I}}", "17", tVal, true},
+	{"$.U.V", "{{$.U.V}}", "v", tVal, true},
+	{"declare in action", "{{$x := $.U.V}}{{$x}}", "v", tVal, true},
+
+	// Type with String method.
+	{"V{6666}.String()", "-{{.V0}}-", "-<6666>-", tVal, true},
+	{"&V{7777}.String()", "-{{.V1}}-", "-<7777>-", tVal, true},
+	{"(*V)(nil).String()", "-{{.V2}}-", "-nilV-", tVal, true},
+
+	// Pointers.
+	{"*int", "{{.PI}}", "23", tVal, true},
+	{"*[]int", "{{.PSI}}", "[21 22 23]", tVal, true},
+	{"*[]int[1]", "{{index .PSI 1}}", "22", tVal, true},
+	{"NIL", "{{.NIL}}", "<nil>", tVal, true},
+
+	// Empty interfaces holding values.
+	{"empty nil", "{{.Empty0}}", "<no value>", tVal, true},
+	{"empty with int", "{{.Empty1}}", "3", tVal, true},
+	{"empty with string", "{{.Empty2}}", "empty2", tVal, true},
+	{"empty with slice", "{{.Empty3}}", "[7 8]", tVal, true},
+	{"empty with struct", "{{.Empty4}}", "{UinEmpty}", tVal, true},
+	{"empty with struct, field", "{{.Empty4.V}}", "UinEmpty", tVal, true},
+
+	// Method calls.
+	{".Method0", "-{{.Method0}}-", "-M0-", tVal, true},
+	{".Method1(1234)", "-{{.Method1 1234}}-", "-1234-", tVal, true},
+	{".Method1(.I)", "-{{.Method1 .I}}-", "-17-", tVal, true},
+	{".Method2(3, .X)", "-{{.Method2 3 .X}}-", "-Method2: 3 x-", tVal, true},
+	{".Method2(.U16, `str`)", "-{{.Method2 .U16 `str`}}-", "-Method2: 16 str-", tVal, true},
+	{".Method2(.U16, $x)", "{{if $x := .X}}-{{.Method2 .U16 $x}}{{end}}-", "-Method2: 16 x-", tVal, true},
+	{"method on var", "{{if $x := .}}-{{$x.Method2 .U16 $x.X}}{{end}}-", "-Method2: 16 x-", tVal, true},
+	{"method on chained var",
+		"{{range .MSIone}}{{if $.U.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
+		"true", tVal, true},
+	{"chained method",
+		"{{range .MSIone}}{{if $.GetU.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
+		"true", tVal, true},
+	{"chained method on variable",
+		"{{with $x := .}}{{with .SI}}{{$.GetU.TrueFalse $.True}}{{end}}{{end}}",
+		"true", tVal, true},
+
+	// Pipelines.
+	{"pipeline", "-{{.Method0 | .Method2 .U16}}-", "-Method2: 16 M0-", tVal, true},
+
+	// If.
+	{"if true", "{{if true}}TRUE{{end}}", "TRUE", tVal, true},
+	{"if false", "{{if false}}TRUE{{else}}FALSE{{end}}", "FALSE", tVal, true},
+	{"if 1", "{{if 1}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0", "{{if 0}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if 1.5", "{{if 1.5}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0.0", "{{if .FloatZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if 1.5i", "{{if 1.5i}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0.0i", "{{if .ComplexZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if emptystring", "{{if ``}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if string", "{{if `notempty`}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if emptyslice", "{{if .SIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if slice", "{{if .SI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if emptymap", "{{if .MSIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if map", "{{if .MSI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if $x with $y int", "{{if $x := true}}{{with $y := .I}}{{$x}},{{$y}}{{end}}{{end}}", "true,17", tVal, true},
+	{"if $x with $x int", "{{if $x := true}}{{with $x := .I}}{{$x}},{{end}}{{$x}}{{end}}", "17,true", tVal, true},
+
+	// Print etc.
+	{"print", `{{print "hello, print"}}`, "hello, print", tVal, true},
+	{"print", `{{print 1 2 3}}`, "1 2 3", tVal, true},
+	{"println", `{{println 1 2 3}}`, "1 2 3\n", tVal, true},
+	{"printf int", `{{printf "%04x" 127}}`, "007f", tVal, true},
+	{"printf float", `{{printf "%g" 3.5}}`, "3.5", tVal, true},
+	{"printf complex", `{{printf "%g" 1+7i}}`, "(1+7i)", tVal, true},
+	{"printf string", `{{printf "%s" "hello"}}`, "hello", tVal, true},
+	{"printf function", `{{printf "%#q" zeroArgs}}`, "`zeroArgs`", tVal, true},
+	{"printf field", `{{printf "%s" .U.V}}`, "v", tVal, true},
+	{"printf method", `{{printf "%s" .Method0}}`, "M0", tVal, true},
+	{"printf dot", `{{with .I}}{{printf "%d" .}}{{end}}`, "17", tVal, true},
+	{"printf var", `{{with $x := .I}}{{printf "%d" $x}}{{end}}`, "17", tVal, true},
+	{"printf lots", `{{printf "%d %s %g %s" 127 "hello" 7-3i .Method0}}`, "127 hello (7-3i) M0", tVal, true},
+
+	// HTML.
+	{"html", `{{html "<script>alert(\"XSS\");</script>"}}`,
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
+	{"html pipeline", `{{printf "<script>alert(\"XSS\");</script>" | html}}`,
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
+
+	// JavaScript.
+	{"js", `{{js .}}`, `It\'d be nice.`, `It'd be nice.`, true},
+
+	// URL query.
+	{"urlquery", `{{"http://www.example.org/"|urlquery}}`, "http%3A%2F%2Fwww.example.org%2F", nil, true},
+
+	// Booleans
+	{"not", "{{not true}} {{not false}}", "false true", nil, true},
+	{"and", "{{and false 0}} {{and 1 0}} {{and 0 true}} {{and 1 1}}", "false 0 0 1", nil, true},
+	{"or", "{{or 0 0}} {{or 1 0}} {{or 0 true}} {{or 1 1}}", "0 1 true 1", nil, true},
+	{"boolean if", "{{if and true 1 `hi`}}TRUE{{else}}FALSE{{end}}", "TRUE", tVal, true},
+	{"boolean if not", "{{if and true 1 `hi` | not}}TRUE{{else}}FALSE{{end}}", "FALSE", nil, true},
+
+	// Indexing.
+	{"slice[0]", "{{index .SI 0}}", "3", tVal, true},
+	{"slice[1]", "{{index .SI 1}}", "4", tVal, true},
+	{"slice[HUGE]", "{{index .SI 10}}", "", tVal, false},
+	{"slice[WRONG]", "{{index .SI `hello`}}", "", tVal, false},
+	{"map[one]", "{{index .MSI `one`}}", "1", tVal, true},
+	{"map[two]", "{{index .MSI `two`}}", "2", tVal, true},
+	{"map[NO]", "{{index .MSI `XXX`}}", "", tVal, true},
+	{"map[WRONG]", "{{index .MSI 10}}", "", tVal, false},
+	{"double index", "{{index .SMSI 1 `eleven`}}", "11", tVal, true},
+
+	// Len.
+	{"slice", "{{len .SI}}", "3", tVal, true},
+	{"map", "{{len .MSI }}", "3", tVal, true},
+	{"len of int", "{{len 3}}", "", tVal, false},
+	{"len of nothing", "{{len .Empty0}}", "", tVal, false},
+
+	// With.
+	{"with true", "{{with true}}{{.}}{{end}}", "true", tVal, true},
+	{"with false", "{{with false}}{{.}}{{else}}FALSE{{end}}", "FALSE", tVal, true},
+	{"with 1", "{{with 1}}{{.}}{{else}}ZERO{{end}}", "1", tVal, true},
+	{"with 0", "{{with 0}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with 1.5", "{{with 1.5}}{{.}}{{else}}ZERO{{end}}", "1.5", tVal, true},
+	{"with 0.0", "{{with .FloatZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with 1.5i", "{{with 1.5i}}{{.}}{{else}}ZERO{{end}}", "(0+1.5i)", tVal, true},
+	{"with 0.0i", "{{with .ComplexZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with emptystring", "{{with ``}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with string", "{{with `notempty`}}{{.}}{{else}}EMPTY{{end}}", "notempty", tVal, true},
+	{"with emptyslice", "{{with .SIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with slice", "{{with .SI}}{{.}}{{else}}EMPTY{{end}}", "[3 4 5]", tVal, true},
+	{"with emptymap", "{{with .MSIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true},
+	{"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "UinEmpty", tVal, true},
+	{"with $x int", "{{with $x := .I}}{{$x}}{{end}}", "17", tVal, true},
+	{"with $x struct.U.V", "{{with $x := $}}{{$x.U.V}}{{end}}", "v", tVal, true},
+	{"with variable and action", "{{with $x := $}}{{$y := $.U.V}}{{$y}}{{end}}", "v", tVal, true},
+
+	// Range.
+	{"range []int", "{{range .SI}}-{{.}}-{{end}}", "-3--4--5-", tVal, true},
+	{"range empty no else", "{{range .SIEmpty}}-{{.}}-{{end}}", "", tVal, true},
+	{"range []int else", "{{range .SI}}-{{.}}-{{else}}EMPTY{{end}}", "-3--4--5-", tVal, true},
+	{"range empty else", "{{range .SIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"range []bool", "{{range .SB}}-{{.}}-{{end}}", "-true--false-", tVal, true},
+	{"range []int method", "{{range .SI | .MAdd .I}}-{{.}}-{{end}}", "-20--21--22-", tVal, true},
+	{"range map", "{{range .MSI | .MSort}}-{{.}}-{{end}}", "-one--three--two-", tVal, true},
+	{"range empty map no else", "{{range .MSIEmpty}}-{{.}}-{{end}}", "", tVal, true},
+	{"range map else", "{{range .MSI | .MSort}}-{{.}}-{{else}}EMPTY{{end}}", "-one--three--two-", tVal, true},
+	{"range empty map else", "{{range .MSIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"range empty interface", "{{range .Empty3}}-{{.}}-{{else}}EMPTY{{end}}", "-7--8-", tVal, true},
+	{"range empty nil", "{{range .Empty0}}-{{.}}-{{end}}", "", tVal, true},
+	{"range $x SI", "{{range $x := .SI}}<{{$x}}>{{end}}", "<3><4><5>", tVal, true},
+	{"range $x $y SI", "{{range $x, $y := .SI}}<{{$x}}={{$y}}>{{end}}", "<0=3><1=4><2=5>", tVal, true},
+	{"range $x MSIone", "{{range $x := .MSIone}}<{{$x}}>{{end}}", "<1>", tVal, true},
+	{"range $x $y MSIone", "{{range $x, $y := .MSIone}}<{{$x}}={{$y}}>{{end}}", "<one=1>", tVal, true},
+	{"range $x PSI", "{{range $x := .PSI}}<{{$x}}>{{end}}", "<21><22><23>", tVal, true},
+	{"declare in range", "{{range $x := .PSI}}<{{$foo:=$x}}{{$x}}>{{end}}", "<21><22><23>", tVal, true},
+
+	// Cute examples.
+	{"or as if true", `{{or .SI "slice is empty"}}`, "[3 4 5]", tVal, true},
+	{"or as if false", `{{or .SIEmpty "slice is empty"}}`, "slice is empty", tVal, true},
+
+	// Error handling.
+	{"error method, error", "{{.EPERM true}}", "", tVal, false},
+	{"error method, no error", "{{.EPERM false}}", "false", tVal, true},
+
+	// Fixed bugs.
+	// Must separate dot and receiver; otherwise args are evaluated with dot set to variable.
+	{"bug0", "{{range .MSIone}}{{if $.Method1 .}}X{{end}}{{end}}", "X", tVal, true},
+	// Do not loop endlessly in indirect for non-empty interfaces.
+	// The bug appears with *interface only; looped forever.
+	{"bug1", "{{.Method0}}", "M0", &iVal, true},
+	// Was taking address of interface field, so method set was empty.
+	{"bug2", "{{$.NonEmptyInterface.Method0}}", "M0", tVal, true},
+	// Struct values were not legal in with - mere oversight.
+	{"bug3", "{{with $}}{{.Method0}}{{end}}", "M0", tVal, true},
+	// Nil interface values in if.
+	{"bug4", "{{if .Empty0}}non-nil{{else}}nil{{end}}", "nil", tVal, true},
+	// Stringer.
+	{"bug5", "{{.Str}}", "foozle", tVal, true},
+}
+
+func zeroArgs() string {
+	return "zeroArgs"
+}
+
+func oneArg(a string) string {
+	return "oneArg=" + a
+}
+
+func testExecute(execTests []execTest, set *Set, t *testing.T) {
+	b := new(bytes.Buffer)
+	funcs := FuncMap{"zeroArgs": zeroArgs, "oneArg": oneArg, "typeOf": typeOf}
+	for _, test := range execTests {
+		tmpl := New(test.name).Funcs(funcs)
+		_, err := tmpl.ParseInSet(test.input, set)
+		if err != nil {
+			t.Errorf("%s: parse error: %s", test.name, err)
+			continue
+		}
+		b.Reset()
+		err = tmpl.Execute(b, test.data)
+		switch {
+		case !test.ok && err == nil:
+			t.Errorf("%s: expected error; got none", test.name)
+			continue
+		case test.ok && err != nil:
+			t.Errorf("%s: unexpected execute error: %s", test.name, err)
+			continue
+		case !test.ok && err != nil:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+		}
+		result := b.String()
+		if result != test.output {
+			t.Errorf("%s: expected\n\t%q\ngot\n\t%q", test.name, test.output, result)
+		}
+	}
+}
+
+func TestExecute(t *testing.T) {
+	testExecute(execTests, nil, t)
+}
+
+// Check that an error from a method flows back to the top.
+func TestExecuteError(t *testing.T) {
+	b := new(bytes.Buffer)
+	tmpl := New("error")
+	_, err := tmpl.Parse("{{.EPERM true}}")
+	if err != nil {
+		t.Fatalf("parse error: %s", err)
+	}
+	err = tmpl.Execute(b, tVal)
+	if err == nil {
+		t.Errorf("expected error; got none")
+	} else if !strings.Contains(err.String(), os.EPERM.String()) {
+		if *debug {
+			fmt.Printf("test execute error: %s\n", err)
+		}
+		t.Errorf("expected os.EPERM; got %s", err)
+	}
+}
+
+func TestJSEscaping(t *testing.T) {
+	testCases := []struct {
+		in, exp string
+	}{
+		{`a`, `a`},
+		{`'foo`, `\'foo`},
+		{`Go "jump" \`, `Go \"jump\" \\`},
+		{`Yukihiro says "今日は世界"`, `Yukihiro says \"今日は世界\"`},
+		{"unprintable \uFDFF", `unprintable \uFDFF`},
+		{`<html>`, `\x3Chtml\x3E`},
+	}
+	for _, tc := range testCases {
+		s := JSEscapeString(tc.in)
+		if s != tc.exp {
+			t.Errorf("JS escaping [%s] got [%s] want [%s]", tc.in, s, tc.exp)
+		}
+	}
+}
+
+// A nice example: walk a binary tree.
+
+type Tree struct {
+	Val         int
+	Left, Right *Tree
+}
+
+const treeTemplate = `
+	{{define "tree"}}
+	[
+		{{.Val}}
+		{{with .Left}}
+			{{template "tree" .}}
+		{{end}}
+		{{with .Right}}
+			{{template "tree" .}}
+		{{end}}
+	]
+	{{end}}
+`
+
+func TestTree(t *testing.T) {
+	var tree = &Tree{
+		1,
+		&Tree{
+			2, &Tree{
+				3,
+				&Tree{
+					4, nil, nil,
+				},
+				nil,
+			},
+			&Tree{
+				5,
+				&Tree{
+					6, nil, nil,
+				},
+				nil,
+			},
+		},
+		&Tree{
+			7,
+			&Tree{
+				8,
+				&Tree{
+					9, nil, nil,
+				},
+				nil,
+			},
+			&Tree{
+				10,
+				&Tree{
+					11, nil, nil,
+				},
+				nil,
+			},
+		},
+	}
+	set := new(Set)
+	_, err := set.Parse(treeTemplate)
+	if err != nil {
+		t.Fatal("parse error:", err)
+	}
+	var b bytes.Buffer
+	err = set.Execute(&b, "tree", tree)
+	if err != nil {
+		t.Fatal("exec error:", err)
+	}
+	stripSpace := func(r int) int {
+		if r == '\t' || r == '\n' {
+			return -1
+		}
+		return r
+	}
+	result := strings.Map(stripSpace, b.String())
+	const expect = "[1[2[3[4]][5[6]]][7[8[9]][10[11]]]]"
+	if result != expect {
+		t.Errorf("expected %q got %q", expect, result)
+	}
+}
diff --git a/src/pkg/template/funcs.go b/src/pkg/template/funcs.go
new file mode 100644
index 000000000..feb1fd82c
--- /dev/null
+++ b/src/pkg/template/funcs.go
@@ -0,0 +1,368 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"reflect"
+	"strings"
+	"unicode"
+	"url"
+	"utf8"
+)
+
+// FuncMap is the type of the map defining the mapping from names to functions.
+// Each function must have either a single return value, or two return values of
+// which the second has type os.Error. If the second argument evaluates to non-nil
+// during execution, execution terminates and Execute returns an error.
+type FuncMap map[string]interface{}
+
+var builtins = FuncMap{
+	"and":      and,
+	"html":     HTMLEscaper,
+	"index":    index,
+	"js":       JSEscaper,
+	"len":      length,
+	"not":      not,
+	"or":       or,
+	"print":    fmt.Sprint,
+	"printf":   fmt.Sprintf,
+	"println":  fmt.Sprintln,
+	"urlquery": URLQueryEscaper,
+}
+
+var builtinFuncs = createValueFuncs(builtins)
+
+// createValueFuncs turns a FuncMap into a map[string]reflect.Value
+func createValueFuncs(funcMap FuncMap) map[string]reflect.Value {
+	m := make(map[string]reflect.Value)
+	addValueFuncs(m, funcMap)
+	return m
+}
+
+// addValueFuncs adds to values the functions in funcs, converting them to reflect.Values.
+func addValueFuncs(out map[string]reflect.Value, in FuncMap) {
+	for name, fn := range in {
+		v := reflect.ValueOf(fn)
+		if v.Kind() != reflect.Func {
+			panic("value for " + name + " not a function")
+		}
+		if !goodFunc(v.Type()) {
+			panic(fmt.Errorf("can't handle multiple results from method/function %q", name))
+		}
+		out[name] = v
+	}
+}
+
+// addFuncs adds to values the functions in funcs. It does no checking of the input -
+// call addValueFuncs first.
+func addFuncs(out, in FuncMap) {
+	for name, fn := range in {
+		out[name] = fn
+	}
+}
+
+// goodFunc checks that the function or method has the right result signature.
+func goodFunc(typ reflect.Type) bool {
+	// We allow functions with 1 result or 2 results where the second is an os.Error.
+	switch {
+	case typ.NumOut() == 1:
+		return true
+	case typ.NumOut() == 2 && typ.Out(1) == osErrorType:
+		return true
+	}
+	return false
+}
+
+// findFunction looks for a function in the template, set, and global map.
+func findFunction(name string, tmpl *Template, set *Set) (reflect.Value, bool) {
+	if tmpl != nil {
+		if fn := tmpl.execFuncs[name]; fn.IsValid() {
+			return fn, true
+		}
+	}
+	if set != nil {
+		if fn := set.execFuncs[name]; fn.IsValid() {
+			return fn, true
+		}
+	}
+	if fn := builtinFuncs[name]; fn.IsValid() {
+		return fn, true
+	}
+	return reflect.Value{}, false
+}
+
+// Indexing.
+
+// index returns the result of indexing its first argument by the following
+// arguments.  Thus "index x 1 2 3" is, in Go syntax, x[1][2][3]. Each
+// indexed item must be a map, slice, or array.
+func index(item interface{}, indices ...interface{}) (interface{}, os.Error) {
+	v := reflect.ValueOf(item)
+	for _, i := range indices {
+		index := reflect.ValueOf(i)
+		var isNil bool
+		if v, isNil = indirect(v); isNil {
+			return nil, fmt.Errorf("index of nil pointer")
+		}
+		switch v.Kind() {
+		case reflect.Array, reflect.Slice:
+			var x int64
+			switch index.Kind() {
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				x = index.Int()
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+				x = int64(index.Uint())
+			default:
+				return nil, fmt.Errorf("cannot index slice/array with type %s", index.Type())
+			}
+			if x < 0 || x >= int64(v.Len()) {
+				return nil, fmt.Errorf("index out of range: %d", x)
+			}
+			v = v.Index(int(x))
+		case reflect.Map:
+			if !index.Type().AssignableTo(v.Type().Key()) {
+				return nil, fmt.Errorf("%s is not index type for %s", index.Type(), v.Type())
+			}
+			if x := v.MapIndex(index); x.IsValid() {
+				v = x
+			} else {
+				v = reflect.Zero(v.Type().Key())
+			}
+		default:
+			return nil, fmt.Errorf("can't index item of type %s", index.Type())
+		}
+	}
+	return v.Interface(), nil
+}
+
+// Length
+
+// length returns the length of the item, with an error if it has no defined length.
+func length(item interface{}) (int, os.Error) {
+	v, isNil := indirect(reflect.ValueOf(item))
+	if isNil {
+		return 0, fmt.Errorf("len of nil pointer")
+	}
+	switch v.Kind() {
+	case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len(), nil
+	}
+	return 0, fmt.Errorf("len of type %s", v.Type())
+}
+
+// Boolean logic.
+
+func truth(a interface{}) bool {
+	t, _ := isTrue(reflect.ValueOf(a))
+	return t
+}
+
+// and computes the Boolean AND of its arguments, returning
+// the first false argument it encounters, or the last argument.
+func and(arg0 interface{}, args ...interface{}) interface{} {
+	if !truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if !truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// or computes the Boolean OR of its arguments, returning
+// the first true argument it encounters, or the last argument.
+func or(arg0 interface{}, args ...interface{}) interface{} {
+	if truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// not returns the Boolean negation of its argument.
+func not(arg interface{}) (truth bool) {
+	truth, _ = isTrue(reflect.ValueOf(arg))
+	return !truth
+}
+
+// HTML escaping.
+
+var (
+	htmlQuot = []byte("&#34;") // shorter than "&quot;"
+	htmlApos = []byte("&#39;") // shorter than "&apos;"
+	htmlAmp  = []byte("&amp;")
+	htmlLt   = []byte("&lt;")
+	htmlGt   = []byte("&gt;")
+)
+
+// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
+func HTMLEscape(w io.Writer, b []byte) {
+	last := 0
+	for i, c := range b {
+		var html []byte
+		switch c {
+		case '"':
+			html = htmlQuot
+		case '\'':
+			html = htmlApos
+		case '&':
+			html = htmlAmp
+		case '<':
+			html = htmlLt
+		case '>':
+			html = htmlGt
+		default:
+			continue
+		}
+		w.Write(b[last:i])
+		w.Write(html)
+		last = i + 1
+	}
+	w.Write(b[last:])
+}
+
+// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
+func HTMLEscapeString(s string) string {
+	// Avoid allocation if we can.
+	if strings.IndexAny(s, `'"&<>`) < 0 {
+		return s
+	}
+	var b bytes.Buffer
+	HTMLEscape(&b, []byte(s))
+	return b.String()
+}
+
+// HTMLEscaper returns the escaped HTML equivalent of the textual
+// representation of its arguments.
+func HTMLEscaper(args ...interface{}) string {
+	ok := false
+	var s string
+	if len(args) == 1 {
+		s, ok = args[0].(string)
+	}
+	if !ok {
+		s = fmt.Sprint(args...)
+	}
+	return HTMLEscapeString(s)
+}
+
+// JavaScript escaping.
+
+var (
+	jsLowUni = []byte(`\u00`)
+	hex      = []byte("0123456789ABCDEF")
+
+	jsBackslash = []byte(`\\`)
+	jsApos      = []byte(`\'`)
+	jsQuot      = []byte(`\"`)
+	jsLt        = []byte(`\x3C`)
+	jsGt        = []byte(`\x3E`)
+)
+
+// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
+func JSEscape(w io.Writer, b []byte) {
+	last := 0
+	for i := 0; i < len(b); i++ {
+		c := b[i]
+
+		if !jsIsSpecial(int(c)) {
+			// fast path: nothing to do
+			continue
+		}
+		w.Write(b[last:i])
+
+		if c < utf8.RuneSelf {
+			// Quotes, slashes and angle brackets get quoted.
+			// Control characters get written as \u00XX.
+			switch c {
+			case '\\':
+				w.Write(jsBackslash)
+			case '\'':
+				w.Write(jsApos)
+			case '"':
+				w.Write(jsQuot)
+			case '<':
+				w.Write(jsLt)
+			case '>':
+				w.Write(jsGt)
+			default:
+				w.Write(jsLowUni)
+				t, b := c>>4, c&0x0f
+				w.Write(hex[t : t+1])
+				w.Write(hex[b : b+1])
+			}
+		} else {
+			// Unicode rune.
+			rune, size := utf8.DecodeRune(b[i:])
+			if unicode.IsPrint(rune) {
+				w.Write(b[i : i+size])
+			} else {
+				// TODO(dsymonds): Do this without fmt?
+				fmt.Fprintf(w, "\\u%04X", rune)
+			}
+			i += size - 1
+		}
+		last = i + 1
+	}
+	w.Write(b[last:])
+}
+
+// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
+func JSEscapeString(s string) string {
+	// Avoid allocation if we can.
+	if strings.IndexFunc(s, jsIsSpecial) < 0 {
+		return s
+	}
+	var b bytes.Buffer
+	JSEscape(&b, []byte(s))
+	return b.String()
+}
+
+func jsIsSpecial(rune int) bool {
+	switch rune {
+	case '\\', '\'', '"', '<', '>':
+		return true
+	}
+	return rune < ' ' || utf8.RuneSelf <= rune
+}
+
+// JSEscaper returns the escaped JavaScript equivalent of the textual
+// representation of its arguments.
+func JSEscaper(args ...interface{}) string {
+	ok := false
+	var s string
+	if len(args) == 1 {
+		s, ok = args[0].(string)
+	}
+	if !ok {
+		s = fmt.Sprint(args...)
+	}
+	return JSEscapeString(s)
+}
+
+// URLQueryEscaper returns the escaped value of the textual representation of
+// its arguments in a form suitable for embedding in a URL query.
+func URLQueryEscaper(args ...interface{}) string {
+	s, ok := "", false
+	if len(args) == 1 {
+		s, ok = args[0].(string)
+	}
+	if !ok {
+		s = fmt.Sprint(args...)
+	}
+	return url.QueryEscape(s)
+}
diff --git a/src/pkg/template/helper.go b/src/pkg/template/helper.go
new file mode 100644
index 000000000..c9b099856
--- /dev/null
+++ b/src/pkg/template/helper.go
@@ -0,0 +1,238 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Helper functions to make constructing templates and sets easier.
+
+package template
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// Functions and methods to parse a single template.
+
+// Must is a helper that wraps a call to a function returning (*Template, os.Error)
+// and panics if the error is non-nil. It is intended for use in variable initializations
+// such as
+//	var t = template.Must(template.New("name").Parse("text"))
+func Must(t *Template, err os.Error) *Template {
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+// ParseFile creates a new Template and parses the template definition from
+// the named file.  The template name is the base name of the file.
+func ParseFile(filename string) (*Template, os.Error) {
+	t := New(filepath.Base(filename))
+	return t.ParseFile(filename)
+}
+
+// parseFileInSet creates a new Template and parses the template
+// definition from the named file. The template name is the base name
+// of the file. It also adds the template to the set. Function bindings are
+// checked against those in the set.
+func parseFileInSet(filename string, set *Set) (*Template, os.Error) {
+	t := New(filepath.Base(filename))
+	return t.parseFileInSet(filename, set)
+}
+
+// ParseFile reads the template definition from a file and parses it to
+// construct an internal representation of the template for execution.
+// The returned template will be nil if an error occurs.
+func (t *Template) ParseFile(filename string) (*Template, os.Error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return t.Parse(string(b))
+}
+
+// parseFileInSet is the same as ParseFile except that function bindings
+// are checked against those in the set and the template is added
+// to the set.
+// The returned template will be nil if an error occurs.
+func (t *Template) parseFileInSet(filename string, set *Set) (*Template, os.Error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return t.ParseInSet(string(b), set)
+}
+
+// Functions and methods to parse a set.
+
+// SetMust is a helper that wraps a call to a function returning (*Set, os.Error)
+// and panics if the error is non-nil. It is intended for use in variable initializations
+// such as
+//	var s = template.SetMust(template.ParseSetFiles("file"))
+func SetMust(s *Set, err os.Error) *Set {
+	if err != nil {
+		panic(err)
+	}
+	return s
+}
+
+// ParseFiles parses the named files into a set of named templates.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
+func (s *Set) ParseFiles(filenames ...string) (*Set, os.Error) {
+	for _, filename := range filenames {
+		b, err := ioutil.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		_, err = s.Parse(string(b))
+		if err != nil {
+			return nil, err
+		}
+	}
+	return s, nil
+}
+
+// ParseSetFiles creates a new Set and parses the set definition from the
+// named files. Each file must be individually parseable.
+func ParseSetFiles(filenames ...string) (*Set, os.Error) {
+	s := new(Set)
+	for _, filename := range filenames {
+		b, err := ioutil.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		_, err = s.Parse(string(b))
+		if err != nil {
+			return nil, err
+		}
+	}
+	return s, nil
+}
+
+// ParseGlob parses the set definition from the files identified by the
+// pattern.  The pattern is processed by filepath.Glob and must match at
+// least one file.
+// If an error occurs, parsing stops and the returned set is nil.
+func (s *Set) ParseGlob(pattern string) (*Set, os.Error) {
+	filenames, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	if len(filenames) == 0 {
+		return nil, fmt.Errorf("pattern matches no files: %#q", pattern)
+	}
+	return s.ParseFiles(filenames...)
+}
+
+// ParseSetGlob creates a new Set and parses the set definition from the
+// files identified by the pattern. The pattern is processed by filepath.Glob
+// and must match at least one file.
+func ParseSetGlob(pattern string) (*Set, os.Error) {
+	set, err := new(Set).ParseGlob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	return set, nil
+}
+
+// Functions and methods to parse stand-alone template files into a set.
+
+// ParseTemplateFiles parses the named template files and adds
+// them to the set. Each template will be named the base name of
+// its file.
+// Unlike with ParseFiles, each file should be a stand-alone template
+// definition suitable for Template.Parse (not Set.Parse); that is, the
+// file does not contain {{define}} clauses. ParseTemplateFiles is
+// therefore equivalent to calling the ParseFile function to create
+// individual templates, which are then added to the set.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
+func (s *Set) ParseTemplateFiles(filenames ...string) (*Set, os.Error) {
+	for _, filename := range filenames {
+		_, err := parseFileInSet(filename, s)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return s, nil
+}
+
+// ParseTemplateGlob parses the template files matched by the
+// patern and adds them to the set. Each template will be named
+// the base name of its file.
+// Unlike with ParseGlob, each file should be a stand-alone template
+// definition suitable for Template.Parse (not Set.Parse); that is, the
+// file does not contain {{define}} clauses. ParseTemplateGlob is
+// therefore equivalent to calling the ParseFile function to create
+// individual templates, which are then added to the set.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
+func (s *Set) ParseTemplateGlob(pattern string) (*Set, os.Error) {
+	filenames, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	for _, filename := range filenames {
+		_, err := parseFileInSet(filename, s)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return s, nil
+}
+
+// ParseTemplateFiles creates a set by parsing the named files,
+// each of which defines a single template. Each template will be
+// named the base name of its file.
+// Unlike with ParseFiles, each file should be a stand-alone template
+// definition suitable for Template.Parse (not Set.Parse); that is, the
+// file does not contain {{define}} clauses. ParseTemplateFiles is
+// therefore equivalent to calling the ParseFile function to create
+// individual templates, which are then added to the set.
+// Each file must be parseable by itself. Parsing stops if an error is
+// encountered.
+func ParseTemplateFiles(filenames ...string) (*Set, os.Error) {
+	set := new(Set)
+	set.init()
+	for _, filename := range filenames {
+		t, err := ParseFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		if err := set.add(t); err != nil {
+			return nil, err
+		}
+	}
+	return set, nil
+}
+
+// ParseTemplateGlob creates a set by parsing the files matched
+// by the pattern, each of which defines a single template. Each
+// template will be named the base name of its file.
+// Unlike with ParseGlob, each file should be a stand-alone template
+// definition suitable for Template.Parse (not Set.Parse); that is, the
+// file does not contain {{define}} clauses. ParseTemplateGlob is
+// therefore equivalent to calling the ParseFile function to create
+// individual templates, which are then added to the set.
+// Each file must be parseable by itself. Parsing stops if an error is
+// encountered.
+func ParseTemplateGlob(pattern string) (*Set, os.Error) {
+	set := new(Set)
+	filenames, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	for _, filename := range filenames {
+		t, err := ParseFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		if err := set.add(t); err != nil {
+			return nil, err
+		}
+	}
+	return set, nil
+}
diff --git a/src/pkg/template/parse.go b/src/pkg/template/parse.go
new file mode 100644
index 000000000..b089c599a
--- /dev/null
+++ b/src/pkg/template/parse.go
@@ -0,0 +1,85 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"os"
+	"reflect"
+	"template/parse"
+)
+
+// Template is the representation of a parsed template.
+type Template struct {
+	name string
+	*parse.Tree
+	// We use two maps, one for parsing and one for execution.
+	// This separation makes the API cleaner since it doesn't
+	// expose reflection to the client.
+	parseFuncs FuncMap
+	execFuncs  map[string]reflect.Value
+	set        *Set // can be nil.
+}
+
+// Name returns the name of the template.
+func (t *Template) Name() string {
+	return t.name
+}
+
+// Parsing.
+
+// New allocates a new template with the given name.
+func New(name string) *Template {
+	return &Template{
+		name:       name,
+		parseFuncs: make(FuncMap),
+		execFuncs:  make(map[string]reflect.Value),
+	}
+}
+
+// Funcs adds the elements of the argument map to the template's function
+// map.  It panics if a value in the map is not a function with appropriate
+// return type.
+// The return value is the template, so calls can be chained.
+func (t *Template) Funcs(funcMap FuncMap) *Template {
+	addValueFuncs(t.execFuncs, funcMap)
+	addFuncs(t.parseFuncs, funcMap)
+	return t
+}
+
+// Parse parses the template definition string to construct an internal
+// representation of the template for execution.
+func (t *Template) Parse(s string) (tmpl *Template, err os.Error) {
+	t.Tree, err = parse.New(t.name).Parse(s, t.parseFuncs, builtins)
+	if err != nil {
+		return nil, err
+	}
+	return t, nil
+}
+
+// ParseInSet parses the template definition string to construct an internal
+// representation of the template for execution. It also adds the template
+// to the set.
+// Function bindings are checked against those in the set.
+func (t *Template) ParseInSet(s string, set *Set) (tmpl *Template, err os.Error) {
+	var setFuncs FuncMap
+	if set != nil {
+		setFuncs = set.parseFuncs
+	}
+	t.Tree, err = parse.New(t.name).Parse(s, t.parseFuncs, setFuncs, builtins)
+	if err != nil {
+		return nil, err
+	}
+	t.addToSet(set)
+	return t, nil
+}
+
+// addToSet adds the template to the set, verifying it's not being double-assigned.
+func (t *Template) addToSet(set *Set) {
+	if set == nil || t.set == set {
+		return
+	}
+	// If double-assigned, Add will panic and we will turn that into an error.
+	set.Add(t)
+}
diff --git a/src/pkg/template/parse/Makefile b/src/pkg/template/parse/Makefile
new file mode 100644
index 000000000..fe6585809
--- /dev/null
+++ b/src/pkg/template/parse/Makefile
@@ -0,0 +1,14 @@
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../../Make.inc
+
+TARG=template/parse
+GOFILES=\
+	lex.go\
+	node.go\
+	parse.go\
+	set.go\
+
+include ../../../Make.pkg
diff --git a/src/pkg/template/parse/lex.go b/src/pkg/template/parse/lex.go
new file mode 100644
index 000000000..7ec4e920b
--- /dev/null
+++ b/src/pkg/template/parse/lex.go
@@ -0,0 +1,474 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+	"utf8"
+)
+
+// item represents a token or text string returned from the scanner.
+type item struct {
+	typ itemType
+	val string
+}
+
+func (i item) String() string {
+	switch {
+	case i.typ == itemEOF:
+		return "EOF"
+	case i.typ == itemError:
+		return i.val
+	case i.typ > itemKeyword:
+		return fmt.Sprintf("<%s>", i.val)
+	case len(i.val) > 10:
+		return fmt.Sprintf("%.10q...", i.val)
+	}
+	return fmt.Sprintf("%q", i.val)
+}
+
+// itemType identifies the type of lex items.
+type itemType int
+
+const (
+	itemError        itemType = iota // error occurred; value is text of error
+	itemBool                         // boolean constant
+	itemChar                         // printable ASCII character; grab bag for comma etc.
+	itemCharConstant                 // character constant
+	itemComplex                      // complex constant (1+2i); imaginary is just a number
+	itemColonEquals                  // colon-equals (':=') introducing a declaration
+	itemEOF
+	itemField      // alphanumeric identifier, starting with '.', possibly chained ('.x.y')
+	itemIdentifier // alphanumeric identifier
+	itemLeftDelim  // left action delimiter
+	itemNumber     // simple number, including imaginary
+	itemPipe       // pipe symbol
+	itemRawString  // raw quoted string (includes quotes)
+	itemRightDelim // right action delimiter
+	itemString     // quoted string (includes quotes)
+	itemText       // plain text
+	itemVariable   // variable starting with '$', such as '$' or  '$1' or '$hello'.
+	// Keywords appear after all the rest.
+	itemKeyword  // used only to delimit the keywords
+	itemDot      // the cursor, spelled '.'.
+	itemDefine   // define keyword
+	itemElse     // else keyword
+	itemEnd      // end keyword
+	itemIf       // if keyword
+	itemRange    // range keyword
+	itemTemplate // template keyword
+	itemWith     // with keyword
+)
+
+// Make the types prettyprint.
+var itemName = map[itemType]string{
+	itemError:        "error",
+	itemBool:         "bool",
+	itemChar:         "char",
+	itemCharConstant: "charconst",
+	itemComplex:      "complex",
+	itemColonEquals:  ":=",
+	itemEOF:          "EOF",
+	itemField:        "field",
+	itemIdentifier:   "identifier",
+	itemLeftDelim:    "left delim",
+	itemNumber:       "number",
+	itemPipe:         "pipe",
+	itemRawString:    "raw string",
+	itemRightDelim:   "right delim",
+	itemString:       "string",
+	itemVariable:     "variable",
+	// keywords
+	itemDot:      ".",
+	itemDefine:   "define",
+	itemElse:     "else",
+	itemIf:       "if",
+	itemEnd:      "end",
+	itemRange:    "range",
+	itemTemplate: "template",
+	itemWith:     "with",
+}
+
+func (i itemType) String() string {
+	s := itemName[i]
+	if s == "" {
+		return fmt.Sprintf("item%d", int(i))
+	}
+	return s
+}
+
+var key = map[string]itemType{
+	".":        itemDot,
+	"define":   itemDefine,
+	"else":     itemElse,
+	"end":      itemEnd,
+	"if":       itemIf,
+	"range":    itemRange,
+	"template": itemTemplate,
+	"with":     itemWith,
+}
+
+const eof = -1
+
+// stateFn represents the state of the scanner as a function that returns the next state.
+type stateFn func(*lexer) stateFn
+
+// lexer holds the state of the scanner.
+type lexer struct {
+	name  string    // the name of the input; used only for error reports.
+	input string    // the string being scanned.
+	state stateFn   // the next lexing function to enter
+	pos   int       // current position in the input.
+	start int       // start position of this item.
+	width int       // width of last rune read from input.
+	items chan item // channel of scanned items.
+}
+
+// next returns the next rune in the input.
+func (l *lexer) next() (rune int) {
+	if l.pos >= len(l.input) {
+		l.width = 0
+		return eof
+	}
+	rune, l.width = utf8.DecodeRuneInString(l.input[l.pos:])
+	l.pos += l.width
+	return rune
+}
+
+// peek returns but does not consume the next rune in the input.
+func (l *lexer) peek() int {
+	rune := l.next()
+	l.backup()
+	return rune
+}
+
+// backup steps back one rune. Can only be called once per call of next.
+func (l *lexer) backup() {
+	l.pos -= l.width
+}
+
+// emit passes an item back to the client.
+func (l *lexer) emit(t itemType) {
+	l.items <- item{t, l.input[l.start:l.pos]}
+	l.start = l.pos
+}
+
+// ignore skips over the pending input before this point.
+func (l *lexer) ignore() {
+	l.start = l.pos
+}
+
+// accept consumes the next rune if it's from the valid set.
+func (l *lexer) accept(valid string) bool {
+	if strings.IndexRune(valid, l.next()) >= 0 {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+// acceptRun consumes a run of runes from the valid set.
+func (l *lexer) acceptRun(valid string) {
+	for strings.IndexRune(valid, l.next()) >= 0 {
+	}
+	l.backup()
+}
+
+// lineNumber reports which line we're on. Doing it this way
+// means we don't have to worry about peek double counting.
+func (l *lexer) lineNumber() int {
+	return 1 + strings.Count(l.input[:l.pos], "\n")
+}
+
+// error returns an error token and terminates the scan by passing
+// back a nil pointer that will be the next state, terminating l.run.
+func (l *lexer) errorf(format string, args ...interface{}) stateFn {
+	l.items <- item{itemError, fmt.Sprintf(format, args...)}
+	return nil
+}
+
+// nextItem returns the next item from the input.
+func (l *lexer) nextItem() item {
+	for {
+		select {
+		case item := <-l.items:
+			return item
+		default:
+			l.state = l.state(l)
+		}
+	}
+	panic("not reached")
+}
+
+// lex creates a new scanner for the input string.
+func lex(name, input string) *lexer {
+	l := &lexer{
+		name:  name,
+		input: input,
+		state: lexText,
+		items: make(chan item, 2), // Two items of buffering is sufficient for all state functions
+	}
+	return l
+}
+
+// state functions
+
+const (
+	leftDelim    = "{{"
+	rightDelim   = "}}"
+	leftComment  = "{{/*"
+	rightComment = "*/}}"
+)
+
+// lexText scans until an opening action delimiter, "{{".
+func lexText(l *lexer) stateFn {
+	for {
+		if strings.HasPrefix(l.input[l.pos:], leftDelim) {
+			if l.pos > l.start {
+				l.emit(itemText)
+			}
+			return lexLeftDelim
+		}
+		if l.next() == eof {
+			break
+		}
+	}
+	// Correctly reached EOF.
+	if l.pos > l.start {
+		l.emit(itemText)
+	}
+	l.emit(itemEOF)
+	return nil
+}
+
+// lexLeftDelim scans the left delimiter, which is known to be present.
+func lexLeftDelim(l *lexer) stateFn {
+	if strings.HasPrefix(l.input[l.pos:], leftComment) {
+		return lexComment
+	}
+	l.pos += len(leftDelim)
+	l.emit(itemLeftDelim)
+	return lexInsideAction
+}
+
+// lexComment scans a comment. The left comment marker is known to be present.
+func lexComment(l *lexer) stateFn {
+	i := strings.Index(l.input[l.pos:], rightComment)
+	if i < 0 {
+		return l.errorf("unclosed comment")
+	}
+	l.pos += i + len(rightComment)
+	l.ignore()
+	return lexText
+}
+
+// lexRightDelim scans the right delimiter, which is known to be present.
+func lexRightDelim(l *lexer) stateFn {
+	l.pos += len(rightDelim)
+	l.emit(itemRightDelim)
+	return lexText
+}
+
+// lexInsideAction scans the elements inside action delimiters.
+func lexInsideAction(l *lexer) stateFn {
+	// Either number, quoted string, or identifier.
+	// Spaces separate and are ignored.
+	// Pipe symbols separate and are emitted.
+	for {
+		if strings.HasPrefix(l.input[l.pos:], rightDelim) {
+			return lexRightDelim
+		}
+		switch r := l.next(); {
+		case r == eof || r == '\n':
+			return l.errorf("unclosed action")
+		case isSpace(r):
+			l.ignore()
+		case r == ':':
+			if l.next() != '=' {
+				return l.errorf("expected :=")
+			}
+			l.emit(itemColonEquals)
+		case r == '|':
+			l.emit(itemPipe)
+		case r == '"':
+			return lexQuote
+		case r == '`':
+			return lexRawQuote
+		case r == '$':
+			return lexIdentifier
+		case r == '\'':
+			return lexChar
+		case r == '.':
+			// special look-ahead for ".field" so we don't break l.backup().
+			if l.pos < len(l.input) {
+				r := l.input[l.pos]
+				if r < '0' || '9' < r {
+					return lexIdentifier // itemDot comes from the keyword table.
+				}
+			}
+			fallthrough // '.' can start a number.
+		case r == '+' || r == '-' || ('0' <= r && r <= '9'):
+			l.backup()
+			return lexNumber
+		case isAlphaNumeric(r):
+			l.backup()
+			return lexIdentifier
+		case r <= unicode.MaxASCII && unicode.IsPrint(r):
+			l.emit(itemChar)
+			return lexInsideAction
+		default:
+			return l.errorf("unrecognized character in action: %#U", r)
+		}
+	}
+	return nil
+}
+
+// lexIdentifier scans an alphanumeric or field.
+func lexIdentifier(l *lexer) stateFn {
+Loop:
+	for {
+		switch r := l.next(); {
+		case isAlphaNumeric(r):
+			// absorb.
+		case r == '.' && (l.input[l.start] == '.' || l.input[l.start] == '$'):
+			// field chaining; absorb into one token.
+		default:
+			l.backup()
+			word := l.input[l.start:l.pos]
+			switch {
+			case key[word] > itemKeyword:
+				l.emit(key[word])
+			case word[0] == '.':
+				l.emit(itemField)
+			case word[0] == '$':
+				l.emit(itemVariable)
+			case word == "true", word == "false":
+				l.emit(itemBool)
+			default:
+				l.emit(itemIdentifier)
+			}
+			break Loop
+		}
+	}
+	return lexInsideAction
+}
+
+// lexChar scans a character constant. The initial quote is already
+// scanned.  Syntax checking is done by the parse.
+func lexChar(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != eof && r != '\n' {
+				break
+			}
+			fallthrough
+		case eof, '\n':
+			return l.errorf("unterminated character constant")
+		case '\'':
+			break Loop
+		}
+	}
+	l.emit(itemCharConstant)
+	return lexInsideAction
+}
+
+// lexNumber scans a number: decimal, octal, hex, float, or imaginary.  This
+// isn't a perfect number scanner - for instance it accepts "." and "0x0.2"
+// and "089" - but when it's wrong the input is invalid and the parser (via
+// strconv) will notice.
+func lexNumber(l *lexer) stateFn {
+	if !l.scanNumber() {
+		return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
+	}
+	if sign := l.peek(); sign == '+' || sign == '-' {
+		// Complex: 1+2i.  No spaces, must end in 'i'.
+		if !l.scanNumber() || l.input[l.pos-1] != 'i' {
+			return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
+		}
+		l.emit(itemComplex)
+	} else {
+		l.emit(itemNumber)
+	}
+	return lexInsideAction
+}
+
+func (l *lexer) scanNumber() bool {
+	// Optional leading sign.
+	l.accept("+-")
+	// Is it hex?
+	digits := "0123456789"
+	if l.accept("0") && l.accept("xX") {
+		digits = "0123456789abcdefABCDEF"
+	}
+	l.acceptRun(digits)
+	if l.accept(".") {
+		l.acceptRun(digits)
+	}
+	if l.accept("eE") {
+		l.accept("+-")
+		l.acceptRun("0123456789")
+	}
+	// Is it imaginary?
+	l.accept("i")
+	// Next thing mustn't be alphanumeric.
+	if isAlphaNumeric(l.peek()) {
+		l.next()
+		return false
+	}
+	return true
+}
+
+// lexQuote scans a quoted string.
+func lexQuote(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != eof && r != '\n' {
+				break
+			}
+			fallthrough
+		case eof, '\n':
+			return l.errorf("unterminated quoted string")
+		case '"':
+			break Loop
+		}
+	}
+	l.emit(itemString)
+	return lexInsideAction
+}
+
+// lexRawQuote scans a raw quoted string.
+func lexRawQuote(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case eof, '\n':
+			return l.errorf("unterminated raw quoted string")
+		case '`':
+			break Loop
+		}
+	}
+	l.emit(itemRawString)
+	return lexInsideAction
+}
+
+// isSpace reports whether r is a space character.
+func isSpace(r int) bool {
+	switch r {
+	case ' ', '\t', '\n', '\r':
+		return true
+	}
+	return false
+}
+
+// isAlphaNumeric reports whether r is an alphabetic, digit, or underscore.
+func isAlphaNumeric(r int) bool {
+	return r == '_' || unicode.IsLetter(r) || unicode.IsDigit(r)
+}
diff --git a/src/pkg/template/parse/lex_test.go b/src/pkg/template/parse/lex_test.go
new file mode 100644
index 000000000..2ad91d5fa
--- /dev/null
+++ b/src/pkg/template/parse/lex_test.go
@@ -0,0 +1,209 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"reflect"
+	"testing"
+)
+
+type lexTest struct {
+	name  string
+	input string
+	items []item
+}
+
+var (
+	tEOF      = item{itemEOF, ""}
+	tLeft     = item{itemLeftDelim, "{{"}
+	tRight    = item{itemRightDelim, "}}"}
+	tRange    = item{itemRange, "range"}
+	tPipe     = item{itemPipe, "|"}
+	tFor      = item{itemIdentifier, "for"}
+	tQuote    = item{itemString, `"abc \n\t\" "`}
+	raw       = "`" + `abc\n\t\" ` + "`"
+	tRawQuote = item{itemRawString, raw}
+)
+
+var lexTests = []lexTest{
+	{"empty", "", []item{tEOF}},
+	{"spaces", " \t\n", []item{{itemText, " \t\n"}, tEOF}},
+	{"text", `now is the time`, []item{{itemText, "now is the time"}, tEOF}},
+	{"text with comment", "hello-{{/* this is a comment */}}-world", []item{
+		{itemText, "hello-"},
+		{itemText, "-world"},
+		tEOF,
+	}},
+	{"punctuation", "{{,@%}}", []item{
+		tLeft,
+		{itemChar, ","},
+		{itemChar, "@"},
+		{itemChar, "%"},
+		tRight,
+		tEOF,
+	}},
+	{"empty action", `{{}}`, []item{tLeft, tRight, tEOF}},
+	{"for", `{{for }}`, []item{tLeft, tFor, tRight, tEOF}},
+	{"quote", `{{"abc \n\t\" "}}`, []item{tLeft, tQuote, tRight, tEOF}},
+	{"raw quote", "{{" + raw + "}}", []item{tLeft, tRawQuote, tRight, tEOF}},
+	{"numbers", "{{1 02 0x14 -7.2i 1e3 +1.2e-4 4.2i 1+2i}}", []item{
+		tLeft,
+		{itemNumber, "1"},
+		{itemNumber, "02"},
+		{itemNumber, "0x14"},
+		{itemNumber, "-7.2i"},
+		{itemNumber, "1e3"},
+		{itemNumber, "+1.2e-4"},
+		{itemNumber, "4.2i"},
+		{itemComplex, "1+2i"},
+		tRight,
+		tEOF,
+	}},
+	{"characters", `{{'a' '\n' '\'' '\\' '\u00FF' '\xFF' '本'}}`, []item{
+		tLeft,
+		{itemCharConstant, `'a'`},
+		{itemCharConstant, `'\n'`},
+		{itemCharConstant, `'\''`},
+		{itemCharConstant, `'\\'`},
+		{itemCharConstant, `'\u00FF'`},
+		{itemCharConstant, `'\xFF'`},
+		{itemCharConstant, `'本'`},
+		tRight,
+		tEOF,
+	}},
+	{"bools", "{{true false}}", []item{
+		tLeft,
+		{itemBool, "true"},
+		{itemBool, "false"},
+		tRight,
+		tEOF,
+	}},
+	{"dot", "{{.}}", []item{
+		tLeft,
+		{itemDot, "."},
+		tRight,
+		tEOF,
+	}},
+	{"dots", "{{.x . .2 .x.y}}", []item{
+		tLeft,
+		{itemField, ".x"},
+		{itemDot, "."},
+		{itemNumber, ".2"},
+		{itemField, ".x.y"},
+		tRight,
+		tEOF,
+	}},
+	{"keywords", "{{range if else end with}}", []item{
+		tLeft,
+		{itemRange, "range"},
+		{itemIf, "if"},
+		{itemElse, "else"},
+		{itemEnd, "end"},
+		{itemWith, "with"},
+		tRight,
+		tEOF,
+	}},
+	{"variables", "{{$c := printf $ $hello $23 $ $var.Field .Method}}", []item{
+		tLeft,
+		{itemVariable, "$c"},
+		{itemColonEquals, ":="},
+		{itemIdentifier, "printf"},
+		{itemVariable, "$"},
+		{itemVariable, "$hello"},
+		{itemVariable, "$23"},
+		{itemVariable, "$"},
+		{itemVariable, "$var.Field"},
+		{itemField, ".Method"},
+		tRight,
+		tEOF,
+	}},
+	{"pipeline", `intro {{echo hi 1.2 |noargs|args 1 "hi"}} outro`, []item{
+		{itemText, "intro "},
+		tLeft,
+		{itemIdentifier, "echo"},
+		{itemIdentifier, "hi"},
+		{itemNumber, "1.2"},
+		tPipe,
+		{itemIdentifier, "noargs"},
+		tPipe,
+		{itemIdentifier, "args"},
+		{itemNumber, "1"},
+		{itemString, `"hi"`},
+		tRight,
+		{itemText, " outro"},
+		tEOF,
+	}},
+	{"declaration", "{{$v := 3}}", []item{
+		tLeft,
+		{itemVariable, "$v"},
+		{itemColonEquals, ":="},
+		{itemNumber, "3"},
+		tRight,
+		tEOF,
+	}},
+	{"2 declarations", "{{$v , $w := 3}}", []item{
+		tLeft,
+		{itemVariable, "$v"},
+		{itemChar, ","},
+		{itemVariable, "$w"},
+		{itemColonEquals, ":="},
+		{itemNumber, "3"},
+		tRight,
+		tEOF,
+	}},
+	// errors
+	{"badchar", "#{{\x01}}", []item{
+		{itemText, "#"},
+		tLeft,
+		{itemError, "unrecognized character in action: U+0001"},
+	}},
+	{"unclosed action", "{{\n}}", []item{
+		tLeft,
+		{itemError, "unclosed action"},
+	}},
+	{"EOF in action", "{{range", []item{
+		tLeft,
+		tRange,
+		{itemError, "unclosed action"},
+	}},
+	{"unclosed quote", "{{\"\n\"}}", []item{
+		tLeft,
+		{itemError, "unterminated quoted string"},
+	}},
+	{"unclosed raw quote", "{{`xx\n`}}", []item{
+		tLeft,
+		{itemError, "unterminated raw quoted string"},
+	}},
+	{"unclosed char constant", "{{'\n}}", []item{
+		tLeft,
+		{itemError, "unterminated character constant"},
+	}},
+	{"bad number", "{{3k}}", []item{
+		tLeft,
+		{itemError, `bad number syntax: "3k"`},
+	}},
+}
+
+// collect gathers the emitted items into a slice.
+func collect(t *lexTest) (items []item) {
+	l := lex(t.name, t.input)
+	for {
+		item := l.nextItem()
+		items = append(items, item)
+		if item.typ == itemEOF || item.typ == itemError {
+			break
+		}
+	}
+	return
+}
+
+func TestLex(t *testing.T) {
+	for _, test := range lexTests {
+		items := collect(&test)
+		if !reflect.DeepEqual(items, test.items) {
+			t.Errorf("%s: got\n\t%v\nexpected\n\t%v", test.name, items, test.items)
+		}
+	}
+}
diff --git a/src/pkg/template/parse/node.go b/src/pkg/template/parse/node.go
new file mode 100644
index 000000000..a917418dc
--- /dev/null
+++ b/src/pkg/template/parse/node.go
@@ -0,0 +1,469 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parse nodes.
+
+package parse
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// A node is an element in the parse tree. The interface is trivial.
+type Node interface {
+	Type() NodeType
+	String() string
+}
+
+// NodeType identifies the type of a parse tree node.
+type NodeType int
+
+// Type returns itself and provides an easy default implementation
+// for embedding in a Node. Embedded in all non-trivial Nodes.
+func (t NodeType) Type() NodeType {
+	return t
+}
+
+const (
+	NodeText       NodeType = iota // Plain text.
+	NodeAction                     // A simple action such as field evaluation.
+	NodeBool                       // A boolean constant.
+	NodeCommand                    // An element of a pipeline.
+	NodeDot                        // The cursor, dot.
+	NodeElse                       // An else action.
+	NodeEnd                        // An end action.
+	NodeField                      // A field or method name.
+	NodeIdentifier                 // An identifier; always a function name.
+	NodeIf                         // An if action.
+	NodeList                       // A list of Nodes.
+	NodeNumber                     // A numerical constant.
+	NodePipe                       // A pipeline of commands.
+	NodeRange                      // A range action.
+	NodeString                     // A string constant.
+	NodeTemplate                   // A template invocation action.
+	NodeVariable                   // A $ variable.
+	NodeWith                       // A with action.
+)
+
+// Nodes.
+
+// ListNode holds a sequence of nodes.
+type ListNode struct {
+	NodeType
+	Nodes []Node // The element nodes in lexical order.
+}
+
+func newList() *ListNode {
+	return &ListNode{NodeType: NodeList}
+}
+
+func (l *ListNode) append(n Node) {
+	l.Nodes = append(l.Nodes, n)
+}
+
+func (l *ListNode) String() string {
+	b := new(bytes.Buffer)
+	fmt.Fprint(b, "[")
+	for _, n := range l.Nodes {
+		fmt.Fprint(b, n)
+	}
+	fmt.Fprint(b, "]")
+	return b.String()
+}
+
+// TextNode holds plain text.
+type TextNode struct {
+	NodeType
+	Text []byte // The text; may span newlines.
+}
+
+func newText(text string) *TextNode {
+	return &TextNode{NodeType: NodeText, Text: []byte(text)}
+}
+
+func (t *TextNode) String() string {
+	return fmt.Sprintf("(text: %q)", t.Text)
+}
+
+// PipeNode holds a pipeline with optional declaration
+type PipeNode struct {
+	NodeType
+	Line int             // The line number in the input.
+	Decl []*VariableNode // Variable declarations in lexical order.
+	Cmds []*CommandNode  // The commands in lexical order.
+}
+
+func newPipeline(line int, decl []*VariableNode) *PipeNode {
+	return &PipeNode{NodeType: NodePipe, Line: line, Decl: decl}
+}
+
+func (p *PipeNode) append(command *CommandNode) {
+	p.Cmds = append(p.Cmds, command)
+}
+
+func (p *PipeNode) String() string {
+	if p.Decl != nil {
+		return fmt.Sprintf("%v := %v", p.Decl, p.Cmds)
+	}
+	return fmt.Sprintf("%v", p.Cmds)
+}
+
+// ActionNode holds an action (something bounded by delimiters).
+// Control actions have their own nodes; ActionNode represents simple
+// ones such as field evaluations.
+type ActionNode struct {
+	NodeType
+	Line int       // The line number in the input.
+	Pipe *PipeNode // The pipeline in the action.
+}
+
+func newAction(line int, pipe *PipeNode) *ActionNode {
+	return &ActionNode{NodeType: NodeAction, Line: line, Pipe: pipe}
+}
+
+func (a *ActionNode) String() string {
+	return fmt.Sprintf("(action: %v)", a.Pipe)
+}
+
+// CommandNode holds a command (a pipeline inside an evaluating action).
+type CommandNode struct {
+	NodeType
+	Args []Node // Arguments in lexical order: Identifier, field, or constant.
+}
+
+func newCommand() *CommandNode {
+	return &CommandNode{NodeType: NodeCommand}
+}
+
+func (c *CommandNode) append(arg Node) {
+	c.Args = append(c.Args, arg)
+}
+
+func (c *CommandNode) String() string {
+	return fmt.Sprintf("(command: %v)", c.Args)
+}
+
+// IdentifierNode holds an identifier.
+type IdentifierNode struct {
+	NodeType
+	Ident string // The identifier's name.
+}
+
+// NewIdentifier returns a new IdentifierNode with the given identifier name.
+func NewIdentifier(ident string) *IdentifierNode {
+	return &IdentifierNode{NodeType: NodeIdentifier, Ident: ident}
+}
+
+func (i *IdentifierNode) String() string {
+	return fmt.Sprintf("I=%s", i.Ident)
+}
+
+// VariableNode holds a list of variable names. The dollar sign is
+// part of the name.
+type VariableNode struct {
+	NodeType
+	Ident []string // Variable names in lexical order.
+}
+
+func newVariable(ident string) *VariableNode {
+	return &VariableNode{NodeType: NodeVariable, Ident: strings.Split(ident, ".")}
+}
+
+func (v *VariableNode) String() string {
+	return fmt.Sprintf("V=%s", v.Ident)
+}
+
+// DotNode holds the special identifier '.'. It is represented by a nil pointer.
+type DotNode bool
+
+func newDot() *DotNode {
+	return nil
+}
+
+func (d *DotNode) Type() NodeType {
+	return NodeDot
+}
+
+func (d *DotNode) String() string {
+	return "{{<.>}}"
+}
+
+// FieldNode holds a field (identifier starting with '.').
+// The names may be chained ('.x.y').
+// The period is dropped from each ident.
+type FieldNode struct {
+	NodeType
+	Ident []string // The identifiers in lexical order.
+}
+
+func newField(ident string) *FieldNode {
+	return &FieldNode{NodeType: NodeField, Ident: strings.Split(ident[1:], ".")} // [1:] to drop leading period
+}
+
+func (f *FieldNode) String() string {
+	return fmt.Sprintf("F=%s", f.Ident)
+}
+
+// BoolNode holds a boolean constant.
+type BoolNode struct {
+	NodeType
+	True bool // The value of the boolean constant.
+}
+
+func newBool(true bool) *BoolNode {
+	return &BoolNode{NodeType: NodeBool, True: true}
+}
+
+func (b *BoolNode) String() string {
+	return fmt.Sprintf("B=%t", b.True)
+}
+
+// NumberNode holds a number: signed or unsigned integer, float, or complex.
+// The value is parsed and stored under all the types that can represent the value.
+// This simulates in a small amount of code the behavior of Go's ideal constants.
+type NumberNode struct {
+	NodeType
+	IsInt      bool       // Number has an integral value.
+	IsUint     bool       // Number has an unsigned integral value.
+	IsFloat    bool       // Number has a floating-point value.
+	IsComplex  bool       // Number is complex.
+	Int64      int64      // The signed integer value.
+	Uint64     uint64     // The unsigned integer value.
+	Float64    float64    // The floating-point value.
+	Complex128 complex128 // The complex value.
+	Text       string     // The original textual representation from the input.
+}
+
+func newNumber(text string, typ itemType) (*NumberNode, os.Error) {
+	n := &NumberNode{NodeType: NodeNumber, Text: text}
+	switch typ {
+	case itemCharConstant:
+		rune, _, tail, err := strconv.UnquoteChar(text[1:], text[0])
+		if err != nil {
+			return nil, err
+		}
+		if tail != "'" {
+			return nil, fmt.Errorf("malformed character constant: %s", text)
+		}
+		n.Int64 = int64(rune)
+		n.IsInt = true
+		n.Uint64 = uint64(rune)
+		n.IsUint = true
+		n.Float64 = float64(rune) // odd but those are the rules.
+		n.IsFloat = true
+		return n, nil
+	case itemComplex:
+		// fmt.Sscan can parse the pair, so let it do the work.
+		if _, err := fmt.Sscan(text, &n.Complex128); err != nil {
+			return nil, err
+		}
+		n.IsComplex = true
+		n.simplifyComplex()
+		return n, nil
+	}
+	// Imaginary constants can only be complex unless they are zero.
+	if len(text) > 0 && text[len(text)-1] == 'i' {
+		f, err := strconv.Atof64(text[:len(text)-1])
+		if err == nil {
+			n.IsComplex = true
+			n.Complex128 = complex(0, f)
+			n.simplifyComplex()
+			return n, nil
+		}
+	}
+	// Do integer test first so we get 0x123 etc.
+	u, err := strconv.Btoui64(text, 0) // will fail for -0; fixed below.
+	if err == nil {
+		n.IsUint = true
+		n.Uint64 = u
+	}
+	i, err := strconv.Btoi64(text, 0)
+	if err == nil {
+		n.IsInt = true
+		n.Int64 = i
+		if i == 0 {
+			n.IsUint = true // in case of -0.
+			n.Uint64 = u
+		}
+	}
+	// If an integer extraction succeeded, promote the float.
+	if n.IsInt {
+		n.IsFloat = true
+		n.Float64 = float64(n.Int64)
+	} else if n.IsUint {
+		n.IsFloat = true
+		n.Float64 = float64(n.Uint64)
+	} else {
+		f, err := strconv.Atof64(text)
+		if err == nil {
+			n.IsFloat = true
+			n.Float64 = f
+			// If a floating-point extraction succeeded, extract the int if needed.
+			if !n.IsInt && float64(int64(f)) == f {
+				n.IsInt = true
+				n.Int64 = int64(f)
+			}
+			if !n.IsUint && float64(uint64(f)) == f {
+				n.IsUint = true
+				n.Uint64 = uint64(f)
+			}
+		}
+	}
+	if !n.IsInt && !n.IsUint && !n.IsFloat {
+		return nil, fmt.Errorf("illegal number syntax: %q", text)
+	}
+	return n, nil
+}
+
+// simplifyComplex pulls out any other types that are represented by the complex number.
+// These all require that the imaginary part be zero.
+func (n *NumberNode) simplifyComplex() {
+	n.IsFloat = imag(n.Complex128) == 0
+	if n.IsFloat {
+		n.Float64 = real(n.Complex128)
+		n.IsInt = float64(int64(n.Float64)) == n.Float64
+		if n.IsInt {
+			n.Int64 = int64(n.Float64)
+		}
+		n.IsUint = float64(uint64(n.Float64)) == n.Float64
+		if n.IsUint {
+			n.Uint64 = uint64(n.Float64)
+		}
+	}
+}
+
+func (n *NumberNode) String() string {
+	return fmt.Sprintf("N=%s", n.Text)
+}
+
+// StringNode holds a string constant. The value has been "unquoted".
+type StringNode struct {
+	NodeType
+	Quoted string // The original text of the string, with quotes.
+	Text   string // The string, after quote processing.
+}
+
+func newString(orig, text string) *StringNode {
+	return &StringNode{NodeType: NodeString, Quoted: orig, Text: text}
+}
+
+func (s *StringNode) String() string {
+	return fmt.Sprintf("S=%#q", s.Text)
+}
+
+// EndNode represents an {{end}} action. It is represented by a nil pointer.
+type EndNode bool
+
+func newEnd() *EndNode {
+	return nil
+}
+
+func (e *EndNode) Type() NodeType {
+	return NodeEnd
+}
+
+func (e *EndNode) String() string {
+	return "{{end}}"
+}
+
+// ElseNode represents an {{else}} action.
+type ElseNode struct {
+	NodeType
+	Line int // The line number in the input.
+}
+
+func newElse(line int) *ElseNode {
+	return &ElseNode{NodeType: NodeElse, Line: line}
+}
+
+func (e *ElseNode) Type() NodeType {
+	return NodeElse
+}
+
+func (e *ElseNode) String() string {
+	return "{{else}}"
+}
+
+// IfNode represents an {{if}} action and its commands.
+type IfNode struct {
+	NodeType
+	Line     int       // The line number in the input.
+	Pipe     *PipeNode // The pipeline to be evaluated.
+	List     *ListNode // What to execute if the value is non-empty.
+	ElseList *ListNode // What to execute if the value is empty (nil if absent).
+}
+
+func newIf(line int, pipe *PipeNode, list, elseList *ListNode) *IfNode {
+	return &IfNode{NodeType: NodeIf, Line: line, Pipe: pipe, List: list, ElseList: elseList}
+}
+
+func (i *IfNode) String() string {
+	if i.ElseList != nil {
+		return fmt.Sprintf("({{if %s}} %s {{else}} %s)", i.Pipe, i.List, i.ElseList)
+	}
+	return fmt.Sprintf("({{if %s}} %s)", i.Pipe, i.List)
+}
+
+// RangeNode represents a {{range}} action and its commands.
+type RangeNode struct {
+	NodeType
+	Line     int       // The line number in the input.
+	Pipe     *PipeNode // The pipeline to be evaluated.
+	List     *ListNode // What to execute if the value is non-empty.
+	ElseList *ListNode // What to execute if the value is empty (nil if absent).
+}
+
+func newRange(line int, pipe *PipeNode, list, elseList *ListNode) *RangeNode {
+	return &RangeNode{NodeType: NodeRange, Line: line, Pipe: pipe, List: list, ElseList: elseList}
+}
+
+func (r *RangeNode) String() string {
+	if r.ElseList != nil {
+		return fmt.Sprintf("({{range %s}} %s {{else}} %s)", r.Pipe, r.List, r.ElseList)
+	}
+	return fmt.Sprintf("({{range %s}} %s)", r.Pipe, r.List)
+}
+
+// TemplateNode represents a {{template}} action.
+type TemplateNode struct {
+	NodeType
+	Line int       // The line number in the input.
+	Name string    // The name of the template (unquoted).
+	Pipe *PipeNode // The command to evaluate as dot for the template.
+}
+
+func newTemplate(line int, name string, pipe *PipeNode) *TemplateNode {
+	return &TemplateNode{NodeType: NodeTemplate, Line: line, Name: name, Pipe: pipe}
+}
+
+func (t *TemplateNode) String() string {
+	if t.Pipe == nil {
+		return fmt.Sprintf("{{template %q}}", t.Name)
+	}
+	return fmt.Sprintf("{{template %q %s}}", t.Name, t.Pipe)
+}
+
+// WithNode represents a {{with}} action and its commands.
+type WithNode struct {
+	NodeType
+	Line     int       // The line number in the input.
+	Pipe     *PipeNode // The pipeline to be evaluated.
+	List     *ListNode // What to execute if the value is non-empty.
+	ElseList *ListNode // What to execute if the value is empty (nil if absent).
+}
+
+func newWith(line int, pipe *PipeNode, list, elseList *ListNode) *WithNode {
+	return &WithNode{NodeType: NodeWith, Line: line, Pipe: pipe, List: list, ElseList: elseList}
+}
+
+func (w *WithNode) String() string {
+	if w.ElseList != nil {
+		return fmt.Sprintf("({{with %s}} %s {{else}} %s)", w.Pipe, w.List, w.ElseList)
+	}
+	return fmt.Sprintf("({{with %s}} %s)", w.Pipe, w.List)
+}
diff --git a/src/pkg/template/parse/parse.go b/src/pkg/template/parse/parse.go
new file mode 100644
index 000000000..9a411a3f3
--- /dev/null
+++ b/src/pkg/template/parse/parse.go
@@ -0,0 +1,436 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package parse builds parse trees for templates.  The grammar is defined
+// in the documents for the template package.
+package parse
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"strconv"
+	"unicode"
+)
+
+// Tree is the representation of a parsed template.
+type Tree struct {
+	Name string    // Name is the name of the template.
+	Root *ListNode // Root is the top-level root of the parse tree.
+	// Parsing only; cleared after parse.
+	funcs     []map[string]interface{}
+	lex       *lexer
+	token     [2]item // two-token lookahead for parser.
+	peekCount int
+	vars      []string // variables defined at the moment.
+}
+
+// next returns the next token.
+func (t *Tree) next() item {
+	if t.peekCount > 0 {
+		t.peekCount--
+	} else {
+		t.token[0] = t.lex.nextItem()
+	}
+	return t.token[t.peekCount]
+}
+
+// backup backs the input stream up one token.
+func (t *Tree) backup() {
+	t.peekCount++
+}
+
+// backup2 backs the input stream up two tokens
+func (t *Tree) backup2(t1 item) {
+	t.token[1] = t1
+	t.peekCount = 2
+}
+
+// peek returns but does not consume the next token.
+func (t *Tree) peek() item {
+	if t.peekCount > 0 {
+		return t.token[t.peekCount-1]
+	}
+	t.peekCount = 1
+	t.token[0] = t.lex.nextItem()
+	return t.token[0]
+}
+
+// Parsing.
+
+// New allocates a new template with the given name.
+func New(name string, funcs ...map[string]interface{}) *Tree {
+	return &Tree{
+		Name:  name,
+		funcs: funcs,
+	}
+}
+
+// errorf formats the error and terminates processing.
+func (t *Tree) errorf(format string, args ...interface{}) {
+	t.Root = nil
+	format = fmt.Sprintf("template: %s:%d: %s", t.Name, t.lex.lineNumber(), format)
+	panic(fmt.Errorf(format, args...))
+}
+
+// error terminates processing.
+func (t *Tree) error(err os.Error) {
+	t.errorf("%s", err)
+}
+
+// expect consumes the next token and guarantees it has the required type.
+func (t *Tree) expect(expected itemType, context string) item {
+	token := t.next()
+	if token.typ != expected {
+		t.errorf("expected %s in %s; got %s", expected, context, token)
+	}
+	return token
+}
+
+// unexpected complains about the token and terminates processing.
+func (t *Tree) unexpected(token item, context string) {
+	t.errorf("unexpected %s in %s", token, context)
+}
+
+// recover is the handler that turns panics into returns from the top level of Parse.
+func (t *Tree) recover(errp *os.Error) {
+	e := recover()
+	if e != nil {
+		if _, ok := e.(runtime.Error); ok {
+			panic(e)
+		}
+		if t != nil {
+			t.stopParse()
+		}
+		*errp = e.(os.Error)
+	}
+	return
+}
+
+// startParse starts the template parsing from the lexer.
+func (t *Tree) startParse(funcs []map[string]interface{}, lex *lexer) {
+	t.Root = nil
+	t.lex = lex
+	t.vars = []string{"$"}
+	t.funcs = funcs
+}
+
+// stopParse terminates parsing.
+func (t *Tree) stopParse() {
+	t.lex = nil
+	t.vars = nil
+	t.funcs = nil
+}
+
+// atEOF returns true if, possibly after spaces, we're at EOF.
+func (t *Tree) atEOF() bool {
+	for {
+		token := t.peek()
+		switch token.typ {
+		case itemEOF:
+			return true
+		case itemText:
+			for _, r := range token.val {
+				if !unicode.IsSpace(r) {
+					return false
+				}
+			}
+			t.next() // skip spaces.
+			continue
+		}
+		break
+	}
+	return false
+}
+
+// Parse parses the template definition string to construct an internal
+// representation of the template for execution.
+func (t *Tree) Parse(s string, funcs ...map[string]interface{}) (tree *Tree, err os.Error) {
+	defer t.recover(&err)
+	t.startParse(funcs, lex(t.Name, s))
+	t.parse(true)
+	t.stopParse()
+	return t, nil
+}
+
+// parse is the helper for Parse.
+// It triggers an error if we expect EOF but don't reach it.
+func (t *Tree) parse(toEOF bool) (next Node) {
+	t.Root, next = t.itemList(true)
+	if toEOF && next != nil {
+		t.errorf("unexpected %s", next)
+	}
+	return next
+}
+
+// itemList:
+//	textOrAction*
+// Terminates at EOF and at {{end}} or {{else}}, which is returned separately.
+// The toEOF flag tells whether we expect to reach EOF.
+func (t *Tree) itemList(toEOF bool) (list *ListNode, next Node) {
+	list = newList()
+	for t.peek().typ != itemEOF {
+		n := t.textOrAction()
+		switch n.Type() {
+		case NodeEnd, NodeElse:
+			return list, n
+		}
+		list.append(n)
+	}
+	if !toEOF {
+		t.unexpected(t.next(), "input")
+	}
+	return list, nil
+}
+
+// textOrAction:
+//	text | action
+func (t *Tree) textOrAction() Node {
+	switch token := t.next(); token.typ {
+	case itemText:
+		return newText(token.val)
+	case itemLeftDelim:
+		return t.action()
+	default:
+		t.unexpected(token, "input")
+	}
+	return nil
+}
+
+// Action:
+//	control
+//	command ("|" command)*
+// Left delim is past. Now get actions.
+// First word could be a keyword such as range.
+func (t *Tree) action() (n Node) {
+	switch token := t.next(); token.typ {
+	case itemElse:
+		return t.elseControl()
+	case itemEnd:
+		return t.endControl()
+	case itemIf:
+		return t.ifControl()
+	case itemRange:
+		return t.rangeControl()
+	case itemTemplate:
+		return t.templateControl()
+	case itemWith:
+		return t.withControl()
+	}
+	t.backup()
+	// Do not pop variables; they persist until "end".
+	return newAction(t.lex.lineNumber(), t.pipeline("command"))
+}
+
+// Pipeline:
+//	field or command
+//	pipeline "|" pipeline
+func (t *Tree) pipeline(context string) (pipe *PipeNode) {
+	var decl []*VariableNode
+	// Are there declarations?
+	for {
+		if v := t.peek(); v.typ == itemVariable {
+			t.next()
+			if next := t.peek(); next.typ == itemColonEquals || next.typ == itemChar {
+				t.next()
+				variable := newVariable(v.val)
+				if len(variable.Ident) != 1 {
+					t.errorf("illegal variable in declaration: %s", v.val)
+				}
+				decl = append(decl, variable)
+				t.vars = append(t.vars, v.val)
+				if next.typ == itemChar && next.val == "," {
+					if context == "range" && len(decl) < 2 {
+						continue
+					}
+					t.errorf("too many declarations in %s", context)
+				}
+			} else {
+				t.backup2(v)
+			}
+		}
+		break
+	}
+	pipe = newPipeline(t.lex.lineNumber(), decl)
+	for {
+		switch token := t.next(); token.typ {
+		case itemRightDelim:
+			if len(pipe.Cmds) == 0 {
+				t.errorf("missing value for %s", context)
+			}
+			return
+		case itemBool, itemCharConstant, itemComplex, itemDot, itemField, itemIdentifier,
+			itemVariable, itemNumber, itemRawString, itemString:
+			t.backup()
+			pipe.append(t.command())
+		default:
+			t.unexpected(token, context)
+		}
+	}
+	return
+}
+
+func (t *Tree) parseControl(context string) (lineNum int, pipe *PipeNode, list, elseList *ListNode) {
+	lineNum = t.lex.lineNumber()
+	defer t.popVars(len(t.vars))
+	pipe = t.pipeline(context)
+	var next Node
+	list, next = t.itemList(false)
+	switch next.Type() {
+	case NodeEnd: //done
+	case NodeElse:
+		elseList, next = t.itemList(false)
+		if next.Type() != NodeEnd {
+			t.errorf("expected end; found %s", next)
+		}
+		elseList = elseList
+	}
+	return lineNum, pipe, list, elseList
+}
+
+// If:
+//	{{if pipeline}} itemList {{end}}
+//	{{if pipeline}} itemList {{else}} itemList {{end}}
+// If keyword is past.
+func (t *Tree) ifControl() Node {
+	return newIf(t.parseControl("if"))
+}
+
+// Range:
+//	{{range pipeline}} itemList {{end}}
+//	{{range pipeline}} itemList {{else}} itemList {{end}}
+// Range keyword is past.
+func (t *Tree) rangeControl() Node {
+	return newRange(t.parseControl("range"))
+}
+
+// With:
+//	{{with pipeline}} itemList {{end}}
+//	{{with pipeline}} itemList {{else}} itemList {{end}}
+// If keyword is past.
+func (t *Tree) withControl() Node {
+	return newWith(t.parseControl("with"))
+}
+
+// End:
+//	{{end}}
+// End keyword is past.
+func (t *Tree) endControl() Node {
+	t.expect(itemRightDelim, "end")
+	return newEnd()
+}
+
+// Else:
+//	{{else}}
+// Else keyword is past.
+func (t *Tree) elseControl() Node {
+	t.expect(itemRightDelim, "else")
+	return newElse(t.lex.lineNumber())
+}
+
+// Template:
+//	{{template stringValue pipeline}}
+// Template keyword is past.  The name must be something that can evaluate
+// to a string.
+func (t *Tree) templateControl() Node {
+	var name string
+	switch token := t.next(); token.typ {
+	case itemString, itemRawString:
+		s, err := strconv.Unquote(token.val)
+		if err != nil {
+			t.error(err)
+		}
+		name = s
+	default:
+		t.unexpected(token, "template invocation")
+	}
+	var pipe *PipeNode
+	if t.next().typ != itemRightDelim {
+		t.backup()
+		// Do not pop variables; they persist until "end".
+		pipe = t.pipeline("template")
+	}
+	return newTemplate(t.lex.lineNumber(), name, pipe)
+}
+
+// command:
+// space-separated arguments up to a pipeline character or right delimiter.
+// we consume the pipe character but leave the right delim to terminate the action.
+func (t *Tree) command() *CommandNode {
+	cmd := newCommand()
+Loop:
+	for {
+		switch token := t.next(); token.typ {
+		case itemRightDelim:
+			t.backup()
+			break Loop
+		case itemPipe:
+			break Loop
+		case itemError:
+			t.errorf("%s", token.val)
+		case itemIdentifier:
+			if !t.hasFunction(token.val) {
+				t.errorf("function %q not defined", token.val)
+			}
+			cmd.append(NewIdentifier(token.val))
+		case itemDot:
+			cmd.append(newDot())
+		case itemVariable:
+			cmd.append(t.useVar(token.val))
+		case itemField:
+			cmd.append(newField(token.val))
+		case itemBool:
+			cmd.append(newBool(token.val == "true"))
+		case itemCharConstant, itemComplex, itemNumber:
+			number, err := newNumber(token.val, token.typ)
+			if err != nil {
+				t.error(err)
+			}
+			cmd.append(number)
+		case itemString, itemRawString:
+			s, err := strconv.Unquote(token.val)
+			if err != nil {
+				t.error(err)
+			}
+			cmd.append(newString(token.val, s))
+		default:
+			t.unexpected(token, "command")
+		}
+	}
+	if len(cmd.Args) == 0 {
+		t.errorf("empty command")
+	}
+	return cmd
+}
+
+// hasFunction reports if a function name exists in the Tree's maps.
+func (t *Tree) hasFunction(name string) bool {
+	for _, funcMap := range t.funcs {
+		if funcMap == nil {
+			continue
+		}
+		if funcMap[name] != nil {
+			return true
+		}
+	}
+	return false
+}
+
+// popVars trims the variable list to the specified length
+func (t *Tree) popVars(n int) {
+	t.vars = t.vars[:n]
+}
+
+// useVar returns a node for a variable reference. It errors if the
+// variable is not defined.
+func (t *Tree) useVar(name string) Node {
+	v := newVariable(name)
+	for _, varName := range t.vars {
+		if varName == v.Ident[0] {
+			return v
+		}
+	}
+	t.errorf("undefined variable %q", v.Ident[0])
+	return nil
+}
diff --git a/src/pkg/template/parse/parse_test.go b/src/pkg/template/parse/parse_test.go
new file mode 100644
index 000000000..1928c319d
--- /dev/null
+++ b/src/pkg/template/parse/parse_test.go
@@ -0,0 +1,259 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"flag"
+	"fmt"
+	"testing"
+)
+
+var debug = flag.Bool("debug", false, "show the errors produced by the tests")
+
+type numberTest struct {
+	text      string
+	isInt     bool
+	isUint    bool
+	isFloat   bool
+	isComplex bool
+	int64
+	uint64
+	float64
+	complex128
+}
+
+var numberTests = []numberTest{
+	// basics
+	{"0", true, true, true, false, 0, 0, 0, 0},
+	{"-0", true, true, true, false, 0, 0, 0, 0}, // check that -0 is a uint.
+	{"73", true, true, true, false, 73, 73, 73, 0},
+	{"073", true, true, true, false, 073, 073, 073, 0},
+	{"0x73", true, true, true, false, 0x73, 0x73, 0x73, 0},
+	{"-73", true, false, true, false, -73, 0, -73, 0},
+	{"+73", true, false, true, false, 73, 0, 73, 0},
+	{"100", true, true, true, false, 100, 100, 100, 0},
+	{"1e9", true, true, true, false, 1e9, 1e9, 1e9, 0},
+	{"-1e9", true, false, true, false, -1e9, 0, -1e9, 0},
+	{"-1.2", false, false, true, false, 0, 0, -1.2, 0},
+	{"1e19", false, true, true, false, 0, 1e19, 1e19, 0},
+	{"-1e19", false, false, true, false, 0, 0, -1e19, 0},
+	{"4i", false, false, false, true, 0, 0, 0, 4i},
+	{"-1.2+4.2i", false, false, false, true, 0, 0, 0, -1.2 + 4.2i},
+	{"073i", false, false, false, true, 0, 0, 0, 73i}, // not octal!
+	// complex with 0 imaginary are float (and maybe integer)
+	{"0i", true, true, true, true, 0, 0, 0, 0},
+	{"-1.2+0i", false, false, true, true, 0, 0, -1.2, -1.2},
+	{"-12+0i", true, false, true, true, -12, 0, -12, -12},
+	{"13+0i", true, true, true, true, 13, 13, 13, 13},
+	// funny bases
+	{"0123", true, true, true, false, 0123, 0123, 0123, 0},
+	{"-0x0", true, true, true, false, 0, 0, 0, 0},
+	{"0xdeadbeef", true, true, true, false, 0xdeadbeef, 0xdeadbeef, 0xdeadbeef, 0},
+	// character constants
+	{`'a'`, true, true, true, false, 'a', 'a', 'a', 0},
+	{`'\n'`, true, true, true, false, '\n', '\n', '\n', 0},
+	{`'\\'`, true, true, true, false, '\\', '\\', '\\', 0},
+	{`'\''`, true, true, true, false, '\'', '\'', '\'', 0},
+	{`'\xFF'`, true, true, true, false, 0xFF, 0xFF, 0xFF, 0},
+	{`'パ'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	{`'\u30d1'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	{`'\U000030d1'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	// some broken syntax
+	{text: "+-2"},
+	{text: "0x123."},
+	{text: "1e."},
+	{text: "0xi."},
+	{text: "1+2."},
+	{text: "'x"},
+	{text: "'xx'"},
+}
+
+func TestNumberParse(t *testing.T) {
+	for _, test := range numberTests {
+		// If fmt.Sscan thinks it's complex, it's complex.  We can't trust the output
+		// because imaginary comes out as a number.
+		var c complex128
+		typ := itemNumber
+		if test.text[0] == '\'' {
+			typ = itemCharConstant
+		} else {
+			_, err := fmt.Sscan(test.text, &c)
+			if err == nil {
+				typ = itemComplex
+			}
+		}
+		n, err := newNumber(test.text, typ)
+		ok := test.isInt || test.isUint || test.isFloat || test.isComplex
+		if ok && err != nil {
+			t.Errorf("unexpected error for %q: %s", test.text, err)
+			continue
+		}
+		if !ok && err == nil {
+			t.Errorf("expected error for %q", test.text)
+			continue
+		}
+		if !ok {
+			if *debug {
+				fmt.Printf("%s\n\t%s\n", test.text, err)
+			}
+			continue
+		}
+		if n.IsComplex != test.isComplex {
+			t.Errorf("complex incorrect for %q; should be %t", test.text, test.isComplex)
+		}
+		if test.isInt {
+			if !n.IsInt {
+				t.Errorf("expected integer for %q", test.text)
+			}
+			if n.Int64 != test.int64 {
+				t.Errorf("int64 for %q should be %d Is %d", test.text, test.int64, n.Int64)
+			}
+		} else if n.IsInt {
+			t.Errorf("did not expect integer for %q", test.text)
+		}
+		if test.isUint {
+			if !n.IsUint {
+				t.Errorf("expected unsigned integer for %q", test.text)
+			}
+			if n.Uint64 != test.uint64 {
+				t.Errorf("uint64 for %q should be %d Is %d", test.text, test.uint64, n.Uint64)
+			}
+		} else if n.IsUint {
+			t.Errorf("did not expect unsigned integer for %q", test.text)
+		}
+		if test.isFloat {
+			if !n.IsFloat {
+				t.Errorf("expected float for %q", test.text)
+			}
+			if n.Float64 != test.float64 {
+				t.Errorf("float64 for %q should be %g Is %g", test.text, test.float64, n.Float64)
+			}
+		} else if n.IsFloat {
+			t.Errorf("did not expect float for %q", test.text)
+		}
+		if test.isComplex {
+			if !n.IsComplex {
+				t.Errorf("expected complex for %q", test.text)
+			}
+			if n.Complex128 != test.complex128 {
+				t.Errorf("complex128 for %q should be %g Is %g", test.text, test.complex128, n.Complex128)
+			}
+		} else if n.IsComplex {
+			t.Errorf("did not expect complex for %q", test.text)
+		}
+	}
+}
+
+type parseTest struct {
+	name   string
+	input  string
+	ok     bool
+	result string
+}
+
+const (
+	noError  = true
+	hasError = false
+)
+
+var parseTests = []parseTest{
+	{"empty", "", noError,
+		`[]`},
+	{"comment", "{{/*\n\n\n*/}}", noError,
+		`[]`},
+	{"spaces", " \t\n", noError,
+		`[(text: " \t\n")]`},
+	{"text", "some text", noError,
+		`[(text: "some text")]`},
+	{"emptyAction", "{{}}", hasError,
+		`[(action: [])]`},
+	{"field", "{{.X}}", noError,
+		`[(action: [(command: [F=[X]])])]`},
+	{"simple command", "{{printf}}", noError,
+		`[(action: [(command: [I=printf])])]`},
+	{"$ invocation", "{{$}}", noError,
+		"[(action: [(command: [V=[$]])])]"},
+	{"variable invocation", "{{with $x := 3}}{{$x 23}}{{end}}", noError,
+		"[({{with [V=[$x]] := [(command: [N=3])]}} [(action: [(command: [V=[$x] N=23])])])]"},
+	{"variable with fields", "{{$.I}}", noError,
+		"[(action: [(command: [V=[$ I]])])]"},
+	{"multi-word command", "{{printf `%d` 23}}", noError,
+		"[(action: [(command: [I=printf S=`%d` N=23])])]"},
+	{"pipeline", "{{.X|.Y}}", noError,
+		`[(action: [(command: [F=[X]]) (command: [F=[Y]])])]`},
+	{"pipeline with decl", "{{$x := .X|.Y}}", noError,
+		`[(action: [V=[$x]] := [(command: [F=[X]]) (command: [F=[Y]])])]`},
+	{"declaration", "{{.X|.Y}}", noError,
+		`[(action: [(command: [F=[X]]) (command: [F=[Y]])])]`},
+	{"simple if", "{{if .X}}hello{{end}}", noError,
+		`[({{if [(command: [F=[X]])]}} [(text: "hello")])]`},
+	{"if with else", "{{if .X}}true{{else}}false{{end}}", noError,
+		`[({{if [(command: [F=[X]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+	{"simple range", "{{range .X}}hello{{end}}", noError,
+		`[({{range [(command: [F=[X]])]}} [(text: "hello")])]`},
+	{"chained field range", "{{range .X.Y.Z}}hello{{end}}", noError,
+		`[({{range [(command: [F=[X Y Z]])]}} [(text: "hello")])]`},
+	{"nested range", "{{range .X}}hello{{range .Y}}goodbye{{end}}{{end}}", noError,
+		`[({{range [(command: [F=[X]])]}} [(text: "hello")({{range [(command: [F=[Y]])]}} [(text: "goodbye")])])]`},
+	{"range with else", "{{range .X}}true{{else}}false{{end}}", noError,
+		`[({{range [(command: [F=[X]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+	{"range over pipeline", "{{range .X|.M}}true{{else}}false{{end}}", noError,
+		`[({{range [(command: [F=[X]]) (command: [F=[M]])]}} [(text: "true")] {{else}} [(text: "false")])]`},
+	{"range []int", "{{range .SI}}{{.}}{{end}}", noError,
+		`[({{range [(command: [F=[SI]])]}} [(action: [(command: [{{<.>}}])])])]`},
+	{"constants", "{{range .SI 1 -3.2i true false 'a'}}{{end}}", noError,
+		`[({{range [(command: [F=[SI] N=1 N=-3.2i B=true B=false N='a'])]}} [])]`},
+	{"template", "{{template `x`}}", noError,
+		`[{{template "x"}}]`},
+	{"template with arg", "{{template `x` .Y}}", noError,
+		`[{{template "x" [(command: [F=[Y]])]}}]`},
+	{"with", "{{with .X}}hello{{end}}", noError,
+		`[({{with [(command: [F=[X]])]}} [(text: "hello")])]`},
+	{"with with else", "{{with .X}}hello{{else}}goodbye{{end}}", noError,
+		`[({{with [(command: [F=[X]])]}} [(text: "hello")] {{else}} [(text: "goodbye")])]`},
+	// Errors.
+	{"unclosed action", "hello{{range", hasError, ""},
+	{"unmatched end", "{{end}}", hasError, ""},
+	{"missing end", "hello{{range .x}}", hasError, ""},
+	{"missing end after else", "hello{{range .x}}{{else}}", hasError, ""},
+	{"undefined function", "hello{{undefined}}", hasError, ""},
+	{"undefined variable", "{{$x}}", hasError, ""},
+	{"variable undefined after end", "{{with $x := 4}}{{end}}{{$x}}", hasError, ""},
+	{"variable undefined in template", "{{template $v}}", hasError, ""},
+	{"declare with field", "{{with $x.Y := 4}}{{end}}", hasError, ""},
+	{"template with field ref", "{{template .X}}", hasError, ""},
+	{"template with var", "{{template $v}}", hasError, ""},
+	{"invalid punctuation", "{{printf 3, 4}}", hasError, ""},
+	{"multidecl outside range", "{{with $v, $u := 3}}{{end}}", hasError, ""},
+	{"too many decls in range", "{{range $u, $v, $w := 3}}{{end}}", hasError, ""},
+}
+
+var builtins = map[string]interface{}{
+	"printf": fmt.Sprintf,
+}
+
+func TestParse(t *testing.T) {
+	for _, test := range parseTests {
+		tmpl, err := New(test.name).Parse(test.input, builtins)
+		switch {
+		case err == nil && !test.ok:
+			t.Errorf("%q: expected error; got none", test.name)
+			continue
+		case err != nil && test.ok:
+			t.Errorf("%q: unexpected error: %v", test.name, err)
+			continue
+		case err != nil && !test.ok:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+			continue
+		}
+		result := tmpl.Root.String()
+		if result != test.result {
+			t.Errorf("%s=(%q): got\n\t%v\nexpected\n\t%v", test.name, test.input, result, test.result)
+		}
+	}
+}
diff --git a/src/pkg/template/parse/set.go b/src/pkg/template/parse/set.go
new file mode 100644
index 000000000..4820da925
--- /dev/null
+++ b/src/pkg/template/parse/set.go
@@ -0,0 +1,50 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+// Set returns a slice of Trees created by parsing the template set
+// definition in the argument string. If an error is encountered,
+// parsing stops and an empty slice is returned with the error.
+func Set(text string, funcs ...map[string]interface{}) (tree map[string]*Tree, err os.Error) {
+	tree = make(map[string]*Tree)
+	defer (*Tree)(nil).recover(&err)
+	lex := lex("set", text)
+	const context = "define clause"
+	for {
+		t := New("set") // name will be updated once we know it.
+		t.startParse(funcs, lex)
+		// Expect EOF or "{{ define name }}".
+		if t.atEOF() {
+			break
+		}
+		t.expect(itemLeftDelim, context)
+		t.expect(itemDefine, context)
+		name := t.expect(itemString, context)
+		t.Name, err = strconv.Unquote(name.val)
+		if err != nil {
+			t.error(err)
+		}
+		t.expect(itemRightDelim, context)
+		end := t.parse(false)
+		if end == nil {
+			t.errorf("unexpected EOF in %s", context)
+		}
+		if end.Type() != NodeEnd {
+			t.errorf("unexpected %s in %s", end, context)
+		}
+		t.stopParse()
+		if _, present := tree[t.Name]; present {
+			return nil, fmt.Errorf("template: %q multiply defined", name)
+		}
+		tree[t.Name] = t
+	}
+	return
+}
diff --git a/src/pkg/template/set.go b/src/pkg/template/set.go
new file mode 100644
index 000000000..f778fd169
--- /dev/null
+++ b/src/pkg/template/set.go
@@ -0,0 +1,108 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"reflect"
+	"template/parse"
+)
+
+// Set holds a set of related templates that can refer to one another by name.
+// The zero value represents an empty set.
+// A template may be a member of multiple sets.
+type Set struct {
+	tmpl       map[string]*Template
+	parseFuncs FuncMap
+	execFuncs  map[string]reflect.Value
+}
+
+func (s *Set) init() {
+	if s.tmpl == nil {
+		s.tmpl = make(map[string]*Template)
+		s.parseFuncs = make(FuncMap)
+		s.execFuncs = make(map[string]reflect.Value)
+	}
+}
+
+// Funcs adds the elements of the argument map to the set's function map.  It
+// panics if a value in the map is not a function with appropriate return
+// type.
+// The return value is the set, so calls can be chained.
+func (s *Set) Funcs(funcMap FuncMap) *Set {
+	s.init()
+	addValueFuncs(s.execFuncs, funcMap)
+	addFuncs(s.parseFuncs, funcMap)
+	return s
+}
+
+// Add adds the argument templates to the set. It panics if two templates
+// with the same name are added or if a template is already a member of
+// a set.
+// The return value is the set, so calls can be chained.
+func (s *Set) Add(templates ...*Template) *Set {
+	for _, t := range templates {
+		if err := s.add(t); err != nil {
+			panic(err)
+		}
+	}
+	return s
+}
+
+// add adds the argument template to the set.
+func (s *Set) add(t *Template) os.Error {
+	s.init()
+	if t.set != nil {
+		return fmt.Errorf("template: %q already in a set", t.name)
+	}
+	if _, ok := s.tmpl[t.name]; ok {
+		return fmt.Errorf("template: %q already defined in set", t.name)
+	}
+	s.tmpl[t.name] = t
+	t.set = s
+	return nil
+}
+
+// Template returns the template with the given name in the set,
+// or nil if there is no such template.
+func (s *Set) Template(name string) *Template {
+	return s.tmpl[name]
+}
+
+// FuncMap returns the set's function map.
+func (s *Set) FuncMap() FuncMap {
+	return s.parseFuncs
+}
+
+// Execute applies the named template to the specified data object, writing
+// the output to wr.
+func (s *Set) Execute(wr io.Writer, name string, data interface{}) os.Error {
+	tmpl := s.tmpl[name]
+	if tmpl == nil {
+		return fmt.Errorf("template: no template %q in set", name)
+	}
+	return tmpl.Execute(wr, data)
+}
+
+// Parse parses a string into a set of named templates.  Parse may be called
+// multiple times for a given set, adding the templates defined in the string
+// to the set.  If a template is redefined, the element in the set is
+// overwritten with the new definition.
+func (s *Set) Parse(text string) (*Set, os.Error) {
+	trees, err := parse.Set(text, s.parseFuncs, builtins)
+	if err != nil {
+		return nil, err
+	}
+	s.init()
+	for name, tree := range trees {
+		tmpl := New(name)
+		tmpl.Tree = tree
+		tmpl.addToSet(s)
+		s.tmpl[name] = tmpl
+	}
+	return s, nil
+}
diff --git a/src/pkg/template/set_test.go b/src/pkg/template/set_test.go
new file mode 100644
index 000000000..f437bc779
--- /dev/null
+++ b/src/pkg/template/set_test.go
@@ -0,0 +1,239 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"fmt"
+	"testing"
+)
+
+const (
+	noError  = true
+	hasError = false
+)
+
+type setParseTest struct {
+	name    string
+	input   string
+	ok      bool
+	names   []string
+	results []string
+}
+
+var setParseTests = []setParseTest{
+	{"empty", "", noError,
+		nil,
+		nil},
+	{"one", `{{define "foo"}} FOO {{end}}`, noError,
+		[]string{"foo"},
+		[]string{`[(text: " FOO ")]`}},
+	{"two", `{{define "foo"}} FOO {{end}}{{define "bar"}} BAR {{end}}`, noError,
+		[]string{"foo", "bar"},
+		[]string{`[(text: " FOO ")]`, `[(text: " BAR ")]`}},
+	// errors
+	{"missing end", `{{define "foo"}} FOO `, hasError,
+		nil,
+		nil},
+	{"malformed name", `{{define "foo}} FOO `, hasError,
+		nil,
+		nil},
+}
+
+func TestSetParse(t *testing.T) {
+	for _, test := range setParseTests {
+		set, err := new(Set).Parse(test.input)
+		switch {
+		case err == nil && !test.ok:
+			t.Errorf("%q: expected error; got none", test.name)
+			continue
+		case err != nil && test.ok:
+			t.Errorf("%q: unexpected error: %v", test.name, err)
+			continue
+		case err != nil && !test.ok:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+			continue
+		}
+		if set == nil {
+			continue
+		}
+		if len(set.tmpl) != len(test.names) {
+			t.Errorf("%s: wrong number of templates; wanted %d got %d", test.name, len(test.names), len(set.tmpl))
+			continue
+		}
+		for i, name := range test.names {
+			tmpl, ok := set.tmpl[name]
+			if !ok {
+				t.Errorf("%s: can't find template %q", test.name, name)
+				continue
+			}
+			result := tmpl.Root.String()
+			if result != test.results[i] {
+				t.Errorf("%s=(%q): got\n\t%v\nexpected\n\t%v", test.name, test.input, result, test.results[i])
+			}
+		}
+	}
+}
+
+var setExecTests = []execTest{
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+	{"invoke x", `{{template "x" .SI}}`, "TEXT", tVal, true},
+	{"invoke x no args", `{{template "x"}}`, "TEXT", tVal, true},
+	{"invoke dot int", `{{template "dot" .I}}`, "17", tVal, true},
+	{"invoke dot []int", `{{template "dot" .SI}}`, "[3 4 5]", tVal, true},
+	{"invoke dotV", `{{template "dotV" .U}}`, "v", tVal, true},
+	{"invoke nested int", `{{template "nested" .I}}`, "17", tVal, true},
+	{"variable declared by template", `{{template "nested" $x=.SI}},{{index $x 1}}`, "[3 4 5],4", tVal, true},
+
+	// User-defined function: test argument evaluator.
+	{"testFunc literal", `{{oneArg "joe"}}`, "oneArg=joe", tVal, true},
+	{"testFunc .", `{{oneArg .}}`, "oneArg=joe", "joe", true},
+}
+
+// These strings are also in testdata/*.
+const setText1 = `
+	{{define "x"}}TEXT{{end}}
+	{{define "dotV"}}{{.V}}{{end}}
+`
+
+const setText2 = `
+	{{define "dot"}}{{.}}{{end}}
+	{{define "nested"}}{{template "dot" .}}{{end}}
+`
+
+func TestSetExecute(t *testing.T) {
+	// Declare a set with a couple of templates first.
+	set := new(Set)
+	_, err := set.Parse(setText1)
+	if err != nil {
+		t.Fatalf("error parsing set: %s", err)
+	}
+	_, err = set.Parse(setText2)
+	if err != nil {
+		t.Fatalf("error parsing set: %s", err)
+	}
+	testExecute(setExecTests, set, t)
+}
+
+func TestSetParseFiles(t *testing.T) {
+	set := new(Set)
+	_, err := set.ParseFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = set.ParseFiles("testdata/file1.tmpl", "testdata/file2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(setExecTests, set, t)
+}
+
+func TestParseSetFiles(t *testing.T) {
+	set := new(Set)
+	_, err := ParseSetFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	set, err = ParseSetFiles("testdata/file1.tmpl", "testdata/file2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(setExecTests, set, t)
+}
+
+func TestSetParseGlob(t *testing.T) {
+	_, err := new(Set).ParseGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = new(Set).ParseGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	set, err := new(Set).ParseGlob("testdata/file*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(setExecTests, set, t)
+}
+
+func TestParseSetGlob(t *testing.T) {
+	_, err := ParseSetGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = ParseSetGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	set, err := ParseSetGlob("testdata/file*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(setExecTests, set, t)
+}
+
+var templateFileExecTests = []execTest{
+	{"test", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\ntemplate2\n", 0, true},
+}
+
+func TestSetParseTemplateFiles(t *testing.T) {
+	_, err := ParseTemplateFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	set, err := new(Set).ParseTemplateFiles("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, set, t)
+}
+
+func TestParseTemplateFiles(t *testing.T) {
+	_, err := ParseTemplateFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	set, err := new(Set).ParseTemplateFiles("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, set, t)
+}
+
+func TestSetParseTemplateGlob(t *testing.T) {
+	_, err := ParseTemplateGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = new(Set).ParseTemplateGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	set, err := new(Set).ParseTemplateGlob("testdata/tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, set, t)
+}
+
+func TestParseTemplateGlob(t *testing.T) {
+	_, err := ParseTemplateGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = ParseTemplateGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	set, err := ParseTemplateGlob("testdata/tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, set, t)
+}
diff --git a/src/pkg/template/testdata/file1.tmpl b/src/pkg/template/testdata/file1.tmpl
new file mode 100644
index 000000000..febf9d9f8
--- /dev/null
+++ b/src/pkg/template/testdata/file1.tmpl
@@ -0,0 +1,2 @@
+{{define "x"}}TEXT{{end}}
+{{define "dotV"}}{{.V}}{{end}}
diff --git a/src/pkg/template/testdata/file2.tmpl b/src/pkg/template/testdata/file2.tmpl
new file mode 100644
index 000000000..39bf6fb9e
--- /dev/null
+++ b/src/pkg/template/testdata/file2.tmpl
@@ -0,0 +1,2 @@
+{{define "dot"}}{{.}}{{end}}
+{{define "nested"}}{{template "dot" .}}{{end}}
diff --git a/src/pkg/template/testdata/tmpl1.tmpl b/src/pkg/template/testdata/tmpl1.tmpl
new file mode 100644
index 000000000..3d15b8173
--- /dev/null
+++ b/src/pkg/template/testdata/tmpl1.tmpl
@@ -0,0 +1 @@
+template1
diff --git a/src/pkg/template/testdata/tmpl2.tmpl b/src/pkg/template/testdata/tmpl2.tmpl
new file mode 100644
index 000000000..a374d2fe7
--- /dev/null
+++ b/src/pkg/template/testdata/tmpl2.tmpl
@@ -0,0 +1 @@
+template2