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-rw-r--r--ext/ply/example/newclasscalc/calc.py155
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diff --git a/ext/ply/example/newclasscalc/calc.py b/ext/ply/example/newclasscalc/calc.py
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+#!/usr/bin/env python
+
+# -----------------------------------------------------------------------------
+# calc.py
+#
+# A simple calculator with variables. This is from O'Reilly's
+# "Lex and Yacc", p. 63.
+#
+# Class-based example contributed to PLY by David McNab.
+#
+# Modified to use new-style classes. Test case.
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0,"../..")
+
+import readline
+import ply.lex as lex
+import ply.yacc as yacc
+import os
+
+class Parser(object):
+ """
+ Base class for a lexer/parser that has the rules defined as methods
+ """
+ tokens = ()
+ precedence = ()
+
+
+ def __init__(self, **kw):
+ self.debug = kw.get('debug', 0)
+ self.names = { }
+ try:
+ modname = os.path.split(os.path.splitext(__file__)[0])[1] + "_" + self.__class__.__name__
+ except:
+ modname = "parser"+"_"+self.__class__.__name__
+ self.debugfile = modname + ".dbg"
+ self.tabmodule = modname + "_" + "parsetab"
+ #print self.debugfile, self.tabmodule
+
+ # Build the lexer and parser
+ lex.lex(module=self, debug=self.debug)
+ yacc.yacc(module=self,
+ debug=self.debug,
+ debugfile=self.debugfile,
+ tabmodule=self.tabmodule)
+
+ def run(self):
+ while 1:
+ try:
+ s = raw_input('calc > ')
+ except EOFError:
+ break
+ if not s: continue
+ yacc.parse(s)
+
+
+class Calc(Parser):
+
+ tokens = (
+ 'NAME','NUMBER',
+ 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
+ 'LPAREN','RPAREN',
+ )
+
+ # Tokens
+
+ t_PLUS = r'\+'
+ t_MINUS = r'-'
+ t_EXP = r'\*\*'
+ t_TIMES = r'\*'
+ t_DIVIDE = r'/'
+ t_EQUALS = r'='
+ t_LPAREN = r'\('
+ t_RPAREN = r'\)'
+ t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
+
+ def t_NUMBER(self, t):
+ r'\d+'
+ try:
+ t.value = int(t.value)
+ except ValueError:
+ print "Integer value too large", t.value
+ t.value = 0
+ #print "parsed number %s" % repr(t.value)
+ return t
+
+ t_ignore = " \t"
+
+ def t_newline(self, t):
+ r'\n+'
+ t.lexer.lineno += t.value.count("\n")
+
+ def t_error(self, t):
+ print "Illegal character '%s'" % t.value[0]
+ t.lexer.skip(1)
+
+ # Parsing rules
+
+ precedence = (
+ ('left','PLUS','MINUS'),
+ ('left','TIMES','DIVIDE'),
+ ('left', 'EXP'),
+ ('right','UMINUS'),
+ )
+
+ def p_statement_assign(self, p):
+ 'statement : NAME EQUALS expression'
+ self.names[p[1]] = p[3]
+
+ def p_statement_expr(self, p):
+ 'statement : expression'
+ print p[1]
+
+ def p_expression_binop(self, p):
+ """
+ expression : expression PLUS expression
+ | expression MINUS expression
+ | expression TIMES expression
+ | expression DIVIDE expression
+ | expression EXP expression
+ """
+ #print [repr(p[i]) for i in range(0,4)]
+ if p[2] == '+' : p[0] = p[1] + p[3]
+ elif p[2] == '-': p[0] = p[1] - p[3]
+ elif p[2] == '*': p[0] = p[1] * p[3]
+ elif p[2] == '/': p[0] = p[1] / p[3]
+ elif p[2] == '**': p[0] = p[1] ** p[3]
+
+ def p_expression_uminus(self, p):
+ 'expression : MINUS expression %prec UMINUS'
+ p[0] = -p[2]
+
+ def p_expression_group(self, p):
+ 'expression : LPAREN expression RPAREN'
+ p[0] = p[2]
+
+ def p_expression_number(self, p):
+ 'expression : NUMBER'
+ p[0] = p[1]
+
+ def p_expression_name(self, p):
+ 'expression : NAME'
+ try:
+ p[0] = self.names[p[1]]
+ except LookupError:
+ print "Undefined name '%s'" % p[1]
+ p[0] = 0
+
+ def p_error(self, p):
+ print "Syntax error at '%s'" % p.value
+
+if __name__ == '__main__':
+ calc = Calc()
+ calc.run()