diff options
Diffstat (limited to 'trunk/src/examples/oc.py')
| -rw-r--r-- | trunk/src/examples/oc.py | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/trunk/src/examples/oc.py b/trunk/src/examples/oc.py new file mode 100644 index 0000000..77ea195 --- /dev/null +++ b/trunk/src/examples/oc.py @@ -0,0 +1,193 @@ +# oc.py
+#
+# A subset-C parser, (BNF taken from 1996 International Obfuscated C Code Contest)
+#
+# Copyright, 2010, Paul McGuire
+#
+"""
+http://www.ioccc.org/1996/august.hint
+
+The following is a description of the OC grammar:
+
+ OC grammar
+ ==========
+ Terminals are in quotes, () is used for bracketing.
+
+ program: decl*
+
+ decl: vardecl
+ fundecl
+
+ vardecl: type NAME ;
+ type NAME "[" INT "]" ;
+
+ fundecl: type NAME "(" args ")" "{" body "}"
+
+ args: /*empty*/
+ ( arg "," )* arg
+
+ arg: type NAME
+
+ body: vardecl* stmt*
+
+ stmt: ifstmt
+ whilestmt
+ dowhilestmt
+ "return" expr ";"
+ expr ";"
+ "{" stmt* "}"
+ ";"
+
+ ifstmt: "if" "(" expr ")" stmt
+ "if" "(" expr ")" stmt "else" stmt
+
+ whilestmt: "while" "(" expr ")" stmt
+
+ dowhilestmt: "do" stmt "while" "(" expr ")" ";"
+
+ expr: expr binop expr
+ unop expr
+ expr "[" expr "]"
+ "(" expr ")"
+ expr "(" exprs ")"
+ NAME
+ INT
+ CHAR
+ STRING
+
+ exprs: /*empty*/
+ (expr ",")* expr
+
+ binop: "+" | "-" | "*" | "/" | "%" |
+ "=" |
+ "<" | "==" | "!="
+
+ unop: "!" | "-" | "*"
+
+ type: "int" stars
+ "char" stars
+
+ stars: "*"*
+"""
+
+from pyparsing import *
+
+LPAR,RPAR,LBRACK,RBRACK,LBRACE,RBRACE,SEMI,COMMA = map(Suppress, "()[]{};,")
+INT = Keyword("int")
+CHAR = Keyword("char")
+WHILE = Keyword("while")
+DO = Keyword("do")
+IF = Keyword("if")
+ELSE = Keyword("else")
+RETURN = Keyword("return")
+
+NAME = Word(alphas+"_", alphanums+"_")
+integer = Regex(r"[+-]?\d+")
+char = Regex(r"'.'")
+string_ = dblQuotedString
+
+INT = Keyword("int")
+CHAR = Keyword("char")
+TYPE = Group((INT | CHAR) + ZeroOrMore("*"))
+
+expr = Forward()
+operand = NAME | integer | char | string_
+expr << (infixNotation(operand,
+ [
+ (oneOf('! - *'), 1, opAssoc.RIGHT),
+ (oneOf('++ --'), 1, opAssoc.RIGHT),
+ (oneOf('++ --'), 1, opAssoc.LEFT),
+ (oneOf('* / %'), 2, opAssoc.LEFT),
+ (oneOf('+ -'), 2, opAssoc.LEFT),
+ (oneOf('< == > <= >= !='), 2, opAssoc.LEFT),
+ (Regex(r'=[^=]'), 2, opAssoc.LEFT),
+ ]) +
+ Optional( LBRACK + expr + RBRACK |
+ LPAR + Group(Optional(delimitedList(expr))) + RPAR )
+ )
+
+stmt = Forward()
+
+ifstmt = IF - LPAR + expr + RPAR + stmt + Optional(ELSE + stmt)
+whilestmt = WHILE - LPAR + expr + RPAR + stmt
+dowhilestmt = DO - stmt + WHILE + LPAR + expr + RPAR + SEMI
+returnstmt = RETURN - expr + SEMI
+
+stmt << Group( ifstmt |
+ whilestmt |
+ dowhilestmt |
+ returnstmt |
+ expr + SEMI |
+ LBRACE + ZeroOrMore(stmt) + RBRACE |
+ SEMI)
+
+vardecl = Group(TYPE + NAME + Optional(LBRACK + integer + RBRACK)) + SEMI
+
+arg = Group(TYPE + NAME)
+body = ZeroOrMore(vardecl) + ZeroOrMore(stmt)
+fundecl = Group(TYPE + NAME + LPAR + Optional(Group(delimitedList(arg))) + RPAR +
+ LBRACE + Group(body) + RBRACE)
+decl = fundecl | vardecl
+program = ZeroOrMore(decl)
+
+program.ignore(cStyleComment)
+
+# set parser element names
+for vname in ("ifstmt whilestmt dowhilestmt returnstmt TYPE "
+ "NAME fundecl vardecl program arg body stmt".split()):
+ v = vars()[vname]
+ v.setName(vname)
+
+#~ for vname in "fundecl stmt".split():
+ #~ v = vars()[vname]
+ #~ v.setDebug()
+
+test = r"""
+/* A factorial program */
+int
+putstr(char *s)
+{
+ while(*s)
+ putchar(*s++);
+}
+
+int
+fac(int n)
+{
+ if (n == 0)
+ return 1;
+ else
+ return n*fac(n-1);
+}
+
+int
+putn(int n)
+{
+ if (9 < n)
+ putn(n / 10);
+ putchar((n%10) + '0');
+}
+
+int
+facpr(int n)
+{
+ putstr("factorial ");
+ putn(n);
+ putstr(" = ");
+ putn(fac(n));
+ putstr("\n");
+}
+
+int
+main()
+{
+ int i;
+ i = 0;
+ while(i < 10)
+ facpr(i++);
+ return 0;
+}
+"""
+
+ast = program.parseString(test,parseAll=True)
+ast.pprint()
|