rply parser + historical implementation

parser.py

@@ -0,0 +1,80 @@
+from __future__ import print_function
+from pprint import pprint
+from rply import ParserGenerator, LexerGenerator
+from rply.token import BaseBox
+
+lg = LexerGenerator()
+lg.add("LPAREN", r"\(")
+lg.add("RPAREN", r"\)")
+lg.add("ATOM", r"[^\s()]+")
+lg.ignore(r"\s+")
+
+pg = ParserGenerator(["LPAREN", "RPAREN", "ATOM"])
+
+
+@pg.error
+def error_handler(token):
+    raise ValueError("unexpected %s" % token.gettokentype())
+
+
+@pg.production("main : sexpr")
+def main(p):
+    return p[0]
+
+
+@pg.production("sexpr : LPAREN expr RPAREN")
+def sexpr(p):
+    return BoxSexpr(p[1])
+
+
+@pg.production("expr : ATOM")
+def atom(p):
+    return BoxAtom(p[0].getstr())
+
+
+@pg.production("expr : ATOM sexpr")
+@pg.production("expr : ATOM expr")
+def sexpr(p):
+    return BoxExpr(BoxAtom(p[0].getstr()), p[1])
+
+lexer = lg.build()
+parser = pg.build()
+
+
+class BoxSexpr(BaseBox):
+    def __init__(self, expr):
+        self.expr = expr
+
+    def expr(self):
+        return self.expr
+
+    def __str__(self):
+        return "( %s )" % (self.expr)
+
+
+class BoxExpr(BaseBox):
+    def __init__(self, atom, expr):
+        self.atom = atom
+        self.expr = expr
+
+    def atom(self):
+        return self.atom
+
+    def expr(self):
+        return self.expr
+
+    def __str__(self):
+        return "%s . ( %s )" % (self.atom, self.expr)
+
+
+class BoxAtom(BaseBox):
+    def __init__(self, atom):
+        self.atom = atom
+
+    def atom(self):
+        return self.atom
+
+    def __str__(self):
+        return "%s" % (self.atom)
+
+print(parser.parse(lexer.lex("(+ 1 (* 3 2))")))