ext/ply/test/yacc_unused.py

   1 # -----------------------------------------------------------------------------
   2 # yacc_unused.py
   3 #
   4 # A grammar with an unused rule
   5 # -----------------------------------------------------------------------------
   6 import sys
   7 sys.tracebacklimit = 0
   8
   9 from calclex import tokens
  10
  11 # Parsing rules
  12 precedence = (
  13     ('left','PLUS','MINUS'),
  14     ('left','TIMES','DIVIDE'),
  15     ('right','UMINUS'),
  16     )
  17
  18 # dictionary of names
  19 names = { }
  20
  21 def p_statement_assign(t):
  22     'statement : NAME EQUALS expression'
  23     names[t[1]] = t[3]
  24
  25 def p_statement_expr(t):
  26     'statement : expression'
  27     print t[1]
  28
  29 def p_expression_binop(t):
  30     '''expression : expression PLUS expression
  31                   | expression MINUS expression
  32                   | expression TIMES expression
  33                   | expression DIVIDE expression'''
  34     if t[2] == '+'  : t[0] = t[1] + t[3]
  35     elif t[2] == '-': t[0] = t[1] - t[3]
  36     elif t[2] == '*': t[0] = t[1] * t[3]
  37     elif t[3] == '/': t[0] = t[1] / t[3]
  38
  39 def p_expression_uminus(t):
  40     'expression : MINUS expression %prec UMINUS'
  41     t[0] = -t[2]
  42
  43 def p_expression_group(t):
  44     'expression : LPAREN expression RPAREN'
  45     t[0] = t[2]
  46
  47 def p_expression_number(t):
  48     'expression : NUMBER'
  49     t[0] = t[1]
  50
  51 def p_expression_name(t):
  52     'expression : NAME'
  53     try:
  54         t[0] = names[t[1]]
  55     except LookupError:
  56         print "Undefined name '%s'" % t[1]
  57         t[0] = 0
  58
  59 def p_expr_list(t):
  60     'exprlist : exprlist COMMA expression'
  61     pass
  62
  63 def p_expr_list_2(t):
  64     'exprlist : expression'
  65     pass
  66
  67
  68 def p_error(t):
  69     print "Syntax error at '%s'" % t.value
  70
  71 import yacc
  72 yacc.yacc()
  73
  74
  75
  76