ext/ply/test/yacc_badprec.py

   1 # -----------------------------------------------------------------------------
   2 # yacc_badprec.py
   3 #
   4 # Bad precedence specifier
   5 # -----------------------------------------------------------------------------
   6 import sys
   7 sys.tracebacklimit = 0
   8
   9 sys.path.insert(0,"..")
  10 import ply.yacc as yacc
  11
  12 from calclex import tokens
  13
  14 # Parsing rules
  15 precedence = "blah"
  16
  17 # dictionary of names
  18 names = { }
  19
  20 def p_statement_assign(t):
  21     'statement : NAME EQUALS expression'
  22     names[t[1]] = t[3]
  23
  24 def p_statement_expr(t):
  25     'statement : expression'
  26     print t[1]
  27
  28 def p_expression_binop(t):
  29     '''expression : expression PLUS expression
  30                   | expression MINUS expression
  31                   | expression TIMES expression
  32                   | expression DIVIDE expression'''
  33     if t[2] == '+'  : t[0] = t[1] + t[3]
  34     elif t[2] == '-': t[0] = t[1] - t[3]
  35     elif t[2] == '*': t[0] = t[1] * t[3]
  36     elif t[3] == '/': t[0] = t[1] / t[3]
  37
  38 def p_expression_uminus(t):
  39     'expression : MINUS expression %prec UMINUS'
  40     t[0] = -t[2]
  41
  42 def p_expression_group(t):
  43     'expression : LPAREN expression RPAREN'
  44     t[0] = t[2]
  45
  46 def p_expression_number(t):
  47     'expression : NUMBER'
  48     t[0] = t[1]
  49
  50 def p_expression_name(t):
  51     'expression : NAME'
  52     try:
  53         t[0] = names[t[1]]
  54     except LookupError:
  55         print "Undefined name '%s'" % t[1]
  56         t[0] = 0
  57
  58 def p_error(t):
  59     print "Syntax error at '%s'" % t.value
  60
  61 yacc.yacc()
  62
  63
  64
  65