1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
|
# pythonGrammarParser.py
#
# Copyright, 2006, by Paul McGuire
#
from pyparsing import *
# should probably read this from the Grammar file provided with the Python source, but
# this just skips that step and inlines the bnf text directly - this grammar was taken from
# Python 2.4.1
#
grammar = """
# Grammar for Python
# Note: Changing the grammar specified in this file will most likely
# require corresponding changes in the parser module
# (../Modules/parsermodule.c). If you can't make the changes to
# that module yourself, please co-ordinate the required changes
# with someone who can; ask around on python-dev for help. Fred
# Drake <fdrake@acm.org> will probably be listening there.
# Commands for Kees Blom's railroad program
#diagram:token NAME
#diagram:token NUMBER
#diagram:token STRING
#diagram:token NEWLINE
#diagram:token ENDMARKER
#diagram:token INDENT
#diagram:output\input python.bla
#diagram:token DEDENT
#diagram:output\textwidth 20.04cm\oddsidemargin 0.0cm\evensidemargin 0.0cm
#diagram:rules
# Start symbols for the grammar:
# single_input is a single interactive statement;
# file_input is a module or sequence of commands read from an input file;
# eval_input is the input for the eval() and input() functions.
# NB: compound_stmt in single_input is followed by extra NEWLINE!
single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
file_input: (NEWLINE | stmt)* ENDMARKER
eval_input: testlist NEWLINE* ENDMARKER
decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
decorators: decorator+
funcdef: [decorators] 'def' NAME parameters ':' suite
parameters: '(' [varargslist] ')'
varargslist: (fpdef ['=' test] ',')* ('*' NAME [',' '**' NAME] | '**' NAME) | fpdef ['=' test] (',' fpdef ['=' test])* [',']
fpdef: NAME | '(' fplist ')'
fplist: fpdef (',' fpdef)* [',']
stmt: simple_stmt | compound_stmt
simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
small_stmt: expr_stmt | print_stmt | del_stmt | pass_stmt | flow_stmt | import_stmt | global_stmt | exec_stmt | assert_stmt
expr_stmt: testlist (augassign testlist | ('=' testlist)*)
augassign: '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '<<=' | '>>=' | '**=' | '//='
# For normal assignments, additional restrictions enforced by the interpreter
print_stmt: 'print' ( [ test (',' test)* [','] ] | '>>' test [ (',' test)+ [','] ] )
del_stmt: 'del' exprlist
pass_stmt: 'pass'
flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
break_stmt: 'break'
continue_stmt: 'continue'
return_stmt: 'return' [testlist]
yield_stmt: 'yield' testlist
raise_stmt: 'raise' [test [',' test [',' test]]]
import_stmt: import_name | import_from
import_name: 'import' dotted_as_names
import_from: 'from' dotted_name 'import' ('*' | '(' import_as_names ')' | import_as_names)
import_as_name: NAME [NAME NAME]
dotted_as_name: dotted_name [NAME NAME]
import_as_names: import_as_name (',' import_as_name)* [',']
dotted_as_names: dotted_as_name (',' dotted_as_name)*
dotted_name: NAME ('.' NAME)*
global_stmt: 'global' NAME (',' NAME)*
exec_stmt: 'exec' expr ['in' test [',' test]]
assert_stmt: 'assert' test [',' test]
#35
compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | funcdef | classdef
if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
while_stmt: 'while' test ':' suite ['else' ':' suite]
for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]
try_stmt: ('try' ':' suite (except_clause ':' suite)+ #diagram:break
['else' ':' suite] | 'try' ':' suite 'finally' ':' suite)
# NB compile.c makes sure that the default except clause is last
except_clause: 'except' [test [',' test]]
suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
test: and_test ('or' and_test)* | lambdef
and_test: not_test ('and' not_test)*
not_test: 'not' not_test | comparison
comparison: expr (comp_op expr)*
comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
expr: xor_expr ('|' xor_expr)*
xor_expr: and_expr ('^' and_expr)*
and_expr: shift_expr ('&' shift_expr)*
shift_expr: arith_expr (('<<'|'>>') arith_expr)*
arith_expr: term (('+'|'-') term)*
term: factor (('*'|'/'|'%'|'//') factor)*
factor: ('+'|'-'|'~') factor | power
power: atom trailer* ['**' factor]
atom: '(' [testlist_gexp] ')' | '[' [listmaker] ']' | '{' [dictmaker] '}' | '`' testlist1 '`' | NAME | NUMBER | STRING+
listmaker: test ( list_for | (',' test)* [','] )
testlist_gexp: test ( gen_for | (',' test)* [','] )
lambdef: 'lambda' [varargslist] ':' test
trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
subscriptlist: subscript (',' subscript)* [',']
subscript: '.' '.' '.' | test | [test] ':' [test] [sliceop]
sliceop: ':' [test]
exprlist: expr (',' expr)* [',']
testlist: test (',' test)* [',']
testlist_safe: test [(',' test)+ [',']]
dictmaker: test ':' test (',' test ':' test)* [',']
classdef: 'class' NAME ['(' testlist ')'] ':' suite
arglist: (argument ',')* (argument [',']| '*' test [',' '**' test] | '**' test)
argument: [test '='] test [gen_for] # Really [keyword '='] test
list_iter: list_for | list_if
list_for: 'for' exprlist 'in' testlist_safe [list_iter]
list_if: 'if' test [list_iter]
gen_iter: gen_for | gen_if
gen_for: 'for' exprlist 'in' test [gen_iter]
gen_if: 'if' test [gen_iter]
testlist1: test (',' test)*
# not used in grammar, but may appear in "node" passed from Parser to Compiler
encoding_decl: NAME
"""
class SemanticGroup(object):
def __init__(self,contents):
self.contents = contents
while self.contents[-1].__class__ == self.__class__:
self.contents = self.contents[:-1] + self.contents[-1].contents
def __str__(self):
return "%s(%s)" % (self.label,
" ".join([isinstance(c,str) and c or str(c) for c in self.contents]) )
class OrList(SemanticGroup):
label = "OR"
pass
class AndList(SemanticGroup):
label = "AND"
pass
class OptionalGroup(SemanticGroup):
label = "OPT"
pass
class Atom(SemanticGroup):
def __init__(self,contents):
if len(contents) > 1:
self.rep = contents[1]
else:
self.rep = ""
if isinstance(contents,str):
self.contents = contents
else:
self.contents = contents[0]
def __str__(self):
return "%s%s" % (self.rep, self.contents)
def makeGroupObject(cls):
def groupAction(s,l,t):
try:
return cls(t[0].asList())
except:
return cls(t)
return groupAction
# bnf punctuation
LPAREN = Suppress("(")
RPAREN = Suppress(")")
LBRACK = Suppress("[")
RBRACK = Suppress("]")
COLON = Suppress(":")
ALT_OP = Suppress("|")
# bnf grammar
ident = Word(alphanums+"_")
bnfToken = Word(alphanums+"_") + ~FollowedBy(":")
repSymbol = oneOf("* +")
bnfExpr = Forward()
optionalTerm = Group(LBRACK + bnfExpr + RBRACK).setParseAction(makeGroupObject(OptionalGroup))
bnfTerm = ( (bnfToken | quotedString | optionalTerm | ( LPAREN + bnfExpr + RPAREN )) + Optional(repSymbol) ).setParseAction(makeGroupObject(Atom))
andList = Group(bnfTerm + OneOrMore(bnfTerm)).setParseAction(makeGroupObject(AndList))
bnfFactor = andList | bnfTerm
orList = Group( bnfFactor + OneOrMore( ALT_OP + bnfFactor ) ).setParseAction(makeGroupObject(OrList))
bnfExpr << ( orList | bnfFactor )
bnfLine = ident + COLON + bnfExpr
bnfComment = "#" + restOfLine
# build return tokens as a dictionary
bnf = Dict(OneOrMore(Group(bnfLine)))
bnf.ignore(bnfComment)
# bnf is defined, parse the grammar text
bnfDefs = bnf.parseString(grammar)
# correct answer is 78
expected = 78
assert len(bnfDefs) == expected, \
"Error, found %d BNF defns, expected %d" % (len(bnfDefs), expected)
# list out defns in order they were parsed (to verify accuracy of parsing)
for k,v in bnfDefs:
print(k,"=",v)
print()
# list out parsed grammar defns (demonstrates dictionary access to parsed tokens)
for k in list(bnfDefs.keys()):
print(k,"=",bnfDefs[k])
|
