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96 lines
2.1 KiB
Python
96 lines
2.1 KiB
Python
from __future__ import print_function
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from rply import ParserGenerator, LexerGenerator
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from rply.token import BaseBox
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lg = LexerGenerator()
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lg.add("LPAREN", r"\(")
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lg.add("RPAREN", r"\)")
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lg.add("QUOTE", r"'")
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lg.add("ATOM", r"[^\s()]+")
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lg.ignore(r"\s+")
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pg = ParserGenerator(["QUOTE", "LPAREN", "RPAREN", "ATOM"])
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@pg.error
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def error_handler(token):
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type = token.gettokentype()
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pos = token.getsourcepos()
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raise ValueError("unexpected %s at (%s, %s)" %
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(type, pos.lineno, pos.colno))
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@pg.production("main : sexpr")
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def main(p):
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return p[0]
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@pg.production("sexpr : ATOM")
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@pg.production("sexpr : QUOTE sexpr")
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@pg.production("sexpr : LPAREN list RPAREN")
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def sexpr(p):
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if p[0].gettokentype() == "ATOM":
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return BoxAtom(p[0].getstr())
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elif p[0].gettokentype() == "QUOTE":
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return BoxQuote(p[1])
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else:
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return p[1]
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@pg.production("list : sexpr")
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@pg.production("list : sexpr list")
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def list(p):
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if len(p) == 1:
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return BoxPair(p[0])
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else:
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return BoxPair(p[0], p[1])
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lexer = lg.build()
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parser = pg.build()
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class BoxQuote(BaseBox):
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def __init__(self, sexpr):
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self.sexpr = sexpr
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def sexpr(self):
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return self.sexpr
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def __str__(self):
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return "' %s" % self.sexpr
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class BoxPair(BaseBox):
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def __init__(self, x, y=None):
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self.x = x
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self.y = y
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def __str__(self):
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if self.y is None:
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y = "NIL"
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else:
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y = self.y
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return "(%s . %s)" % (self.x, y)
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class BoxAtom(BaseBox):
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def __init__(self, atom):
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self.atom = atom
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def atom(self):
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return self.atom
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def __str__(self):
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return "%s" % (self.atom)
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print(parser.parse(lexer.lex("1")))
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print(parser.parse(lexer.lex("'1")))
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print(parser.parse(lexer.lex("+")))
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print(parser.parse(lexer.lex("'+")))
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print(parser.parse(lexer.lex("(+ 1 2)")))
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print(parser.parse(lexer.lex("'(+ 1 2)")))
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print(parser.parse(lexer.lex("(+ 1 (* 3 2))")))
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print(parser.parse(lexer.lex("'(+ 1 (* 3 2))")))
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print(parser.parse(lexer.lex("(+ (* 4 5) (* 3 2))")))
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print(parser.parse(lexer.lex("(+ '(* 4 5) (* 3 2))")))
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