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quote + simpler recursive descent (less boxing)

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Loic Nageleisen 2013-10-03 12:27:22 +02:00
parent 12da94d927
commit 91020ddfe6
1 changed files with 47 additions and 31 deletions
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76
parser.py
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@ -1,20 +1,23 @@
from __future__ import print_function from __future__ import print_function
from pprint import pprint
from rply import ParserGenerator, LexerGenerator from rply import ParserGenerator, LexerGenerator
from rply.token import BaseBox from rply.token import BaseBox
lg = LexerGenerator() lg = LexerGenerator()
lg.add("LPAREN", r"\(") lg.add("LPAREN", r"\(")
lg.add("RPAREN", r"\)") lg.add("RPAREN", r"\)")
lg.add("QUOTE", r"'")
lg.add("ATOM", r"[^\s()]+") lg.add("ATOM", r"[^\s()]+")
lg.ignore(r"\s+") lg.ignore(r"\s+")
pg = ParserGenerator(["LPAREN", "RPAREN", "ATOM"]) pg = ParserGenerator(["QUOTE", "LPAREN", "RPAREN", "ATOM"])
@pg.error @pg.error
def error_handler(token): def error_handler(token):
raise ValueError("unexpected %s" % token.gettokentype()) type = token.gettokentype()
pos = token.getsourcepos()
raise ValueError("unexpected %s at (%s, %s)" %
(type, pos.lineno, pos.colno))
@pg.production("main : sexpr") @pg.production("main : sexpr")
@ -22,49 +25,52 @@ def main(p):
return p[0] return p[0]
@pg.production("sexpr : LPAREN expr RPAREN") @pg.production("sexpr : ATOM")
@pg.production("sexpr : QUOTE sexpr")
@pg.production("sexpr : LPAREN list RPAREN")
def sexpr(p): def sexpr(p):
return BoxSexpr(p[1]) if p[0].gettokentype() == "ATOM":
@pg.production("expr : ATOM")
def atom(p):
return BoxAtom(p[0].getstr()) return BoxAtom(p[0].getstr())
elif p[0].gettokentype() == "QUOTE":
return BoxQuote(p[1])
else:
return p[1]
@pg.production("expr : ATOM sexpr") @pg.production("list : sexpr")
@pg.production("expr : ATOM expr") @pg.production("list : sexpr list")
def sexpr(p): def list(p):
return BoxExpr(BoxAtom(p[0].getstr()), p[1]) if len(p) == 1:
return BoxPair(p[0])
else:
return BoxPair(p[0], p[1])
lexer = lg.build() lexer = lg.build()
parser = pg.build() parser = pg.build()
class BoxSexpr(BaseBox): class BoxQuote(BaseBox):
def __init__(self, expr): def __init__(self, sexpr):
self.expr = expr self.sexpr = sexpr
def expr(self): def sexpr(self):
return self.expr return self.sexpr
def __str__(self): def __str__(self):
return "( %s )" % (self.expr) return "' %s" % self.sexpr
class BoxExpr(BaseBox): class BoxPair(BaseBox):
def __init__(self, atom, expr): def __init__(self, x, y=None):
self.atom = atom self.x = x
self.expr = expr self.y = y
def atom(self):
return self.atom
def expr(self):
return self.expr
def __str__(self): def __str__(self):
return "%s . ( %s )" % (self.atom, self.expr) if self.y is None:
y = "NIL"
else:
y = self.y
return "(%s . %s)" % (self.x, y)
class BoxAtom(BaseBox): class BoxAtom(BaseBox):
@ -77,4 +83,14 @@ class BoxAtom(BaseBox):
def __str__(self): def __str__(self):
return "%s" % (self.atom) return "%s" % (self.atom)
print(parser.parse(lexer.lex("1")))
print(parser.parse(lexer.lex("'1")))
print(parser.parse(lexer.lex("+")))
print(parser.parse(lexer.lex("'+")))
print(parser.parse(lexer.lex("(+ 1 2)")))
print(parser.parse(lexer.lex("'(+ 1 2)")))
print(parser.parse(lexer.lex("(+ 1 (* 3 2))"))) print(parser.parse(lexer.lex("(+ 1 (* 3 2))")))
print(parser.parse(lexer.lex("'(+ 1 (* 3 2))")))
print(parser.parse(lexer.lex("(+ (* 4 5) (* 3 2))")))
print(parser.parse(lexer.lex("(+ '(* 4 5) (* 3 2))")))