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

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<ais523> ` tar -xf ply-3.8.tar.gz
author HackBot
date Wed, 23 Mar 2016 02:40:16 +0000
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7266:61a39a120dee 7267:343ff337a19b
1 # -----------------------------------------------------------------------------
2 # yacc_rr.py
3 #
4 # A grammar with a reduce/reduce conflict
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','PLUS','MINUS'),
16 ('left','TIMES','DIVIDE'),
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_assign_2(t):
28 'statement : NAME EQUALS NUMBER'
29 names[t[1]] = t[3]
30
31 def p_statement_expr(t):
32 'statement : expression'
33 print(t[1])
34
35 def p_expression_binop(t):
36 '''expression : expression PLUS expression
37 | expression MINUS expression
38 | expression TIMES expression
39 | expression DIVIDE expression'''
40 if t[2] == '+' : t[0] = t[1] + t[3]
41 elif t[2] == '-': t[0] = t[1] - t[3]
42 elif t[2] == '*': t[0] = t[1] * t[3]
43 elif t[2] == '/': t[0] = t[1] / t[3]
44
45 def p_expression_uminus(t):
46 'expression : MINUS expression %prec UMINUS'
47 t[0] = -t[2]
48
49 def p_expression_group(t):
50 'expression : LPAREN expression RPAREN'
51 t[0] = t[2]
52
53 def p_expression_number(t):
54 'expression : NUMBER'
55 t[0] = t[1]
56
57 def p_expression_name(t):
58 'expression : NAME'
59 try:
60 t[0] = names[t[1]]
61 except LookupError:
62 print("Undefined name '%s'" % t[1])
63 t[0] = 0
64
65 def p_error(t):
66 print("Syntax error at '%s'" % t.value)
67
68 yacc.yacc()
69
70
71
72