Mercurial > repo
view ply-3.8/test/yacc_uprec.py @ 8502:da219b3cc5ba
<hppavilion[1]> learn HackEgo, also known as HackBot, is a bot that runs arbitrary commands on Unix. See `help for info on using it. You should totally try to hax0r it! Make sure you assume a spherical cow in a vacuum. HackEgo is the slowest bot in all Mexico!
author | HackBot |
---|---|
date | Thu, 16 Jun 2016 17:21:52 +0000 |
parents | 343ff337a19b |
children |
line wrap: on
line source
# ----------------------------------------------------------------------------- # yacc_uprec.py # # A grammar with a bad %prec specifier # ----------------------------------------------------------------------------- import sys if ".." not in sys.path: sys.path.insert(0,"..") import ply.yacc as yacc from calclex import tokens # Parsing rules # dictionary of names names = { } def p_statement_assign(t): 'statement : NAME EQUALS expression' names[t[1]] = t[3] def p_statement_expr(t): 'statement : expression' print(t[1]) def p_expression_binop(t): '''expression : expression PLUS expression | expression MINUS expression | expression TIMES expression | expression DIVIDE expression''' if t[2] == '+' : t[0] = t[1] + t[3] elif t[2] == '-': t[0] = t[1] - t[3] elif t[2] == '*': t[0] = t[1] * t[3] elif t[2] == '/': t[0] = t[1] / t[3] def p_expression_uminus(t): 'expression : MINUS expression %prec UMINUS' t[0] = -t[2] def p_expression_group(t): 'expression : LPAREN expression RPAREN' t[0] = t[2] def p_expression_number(t): 'expression : NUMBER' t[0] = t[1] def p_expression_name(t): 'expression : NAME' try: t[0] = names[t[1]] except LookupError: print("Undefined name '%s'" % t[1]) t[0] = 0 def p_error(t): print("Syntax error at '%s'" % t.value) yacc.yacc()