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comparison ply-3.8/test/yacc_literal.py @ 7267:343ff337a19b

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author HackBot
date Wed, 23 Mar 2016 02:40:16 +0000
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7266:61a39a120dee 7267:343ff337a19b
1 # -----------------------------------------------------------------------------
2 # yacc_literal.py
3 #
4 # Grammar with bad literal characters
5 # -----------------------------------------------------------------------------
6 import sys
7
8 if ".." not in sys.path: sys.path.insert(0,"..")
9 import ply.yacc as yacc
10
11 from calclex import tokens
12
13 # Parsing rules
14 precedence = (
15 ('left','+','-'),
16 ('left','*','/'),
17 ('right','UMINUS'),
18 )
19
20 # dictionary of names
21 names = { }
22
23 def p_statement_assign(t):
24 'statement : NAME EQUALS expression'
25 names[t[1]] = t[3]
26
27 def p_statement_expr(t):
28 'statement : expression'
29 print(t[1])
30
31 def p_expression_binop(t):
32 '''expression : expression '+' expression
33 | expression '-' expression
34 | expression '*' expression
35 | expression '/' expression
36 | expression '**' expression '''
37 if t[2] == '+' : t[0] = t[1] + t[3]
38 elif t[2] == '-': t[0] = t[1] - t[3]
39 elif t[2] == '*': t[0] = t[1] * t[3]
40 elif t[2] == '/': t[0] = t[1] / t[3]
41
42 def p_expression_uminus(t):
43 'expression : MINUS expression %prec UMINUS'
44 t[0] = -t[2]
45
46 def p_expression_group(t):
47 'expression : LPAREN expression RPAREN'
48 t[0] = t[2]
49
50 def p_expression_number(t):
51 'expression : NUMBER'
52 t[0] = t[1]
53
54 def p_expression_name(t):
55 'expression : NAME'
56 try:
57 t[0] = names[t[1]]
58 except LookupError:
59 print("Undefined name '%s'" % t[1])
60 t[0] = 0
61
62 def p_error(t):
63 print("Syntax error at '%s'" % t.value)
64
65 yacc.yacc()
66
67
68
69