yacc_badtok.py (4479:61d3ed46e373) yacc_badtok.py (6498:e21e9ab5fad0)
1# -----------------------------------------------------------------------------
2# yacc_badtok.py
3#
4# A grammar, but tokens is a bad datatype
5# -----------------------------------------------------------------------------
6
7import sys
1# -----------------------------------------------------------------------------
2# yacc_badtok.py
3#
4# A grammar, but tokens is a bad datatype
5# -----------------------------------------------------------------------------
6
7import sys
8sys.tracebacklimit = 0
9
10sys.path.insert(0,"..")
8if ".." not in sys.path: sys.path.insert(0,"..")
11import ply.yacc as yacc
12
13tokens = "Hello"
14
15# Parsing rules
16precedence = (
17 ('left','PLUS','MINUS'),
18 ('left','TIMES','DIVIDE'),

--- 4 unchanged lines hidden (view full) ---

23names = { }
24
25def p_statement_assign(t):
26 'statement : NAME EQUALS expression'
27 names[t[1]] = t[3]
28
29def p_statement_expr(t):
30 'statement : expression'
9import ply.yacc as yacc
10
11tokens = "Hello"
12
13# Parsing rules
14precedence = (
15 ('left','PLUS','MINUS'),
16 ('left','TIMES','DIVIDE'),

--- 4 unchanged lines hidden (view full) ---

21names = { }
22
23def p_statement_assign(t):
24 'statement : NAME EQUALS expression'
25 names[t[1]] = t[3]
26
27def p_statement_expr(t):
28 'statement : expression'
31 print t[1]
29 print(t[1])
32
33def p_expression_binop(t):
34 '''expression : expression PLUS expression
35 | expression MINUS expression
36 | expression TIMES expression
37 | expression DIVIDE expression'''
38 if 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]
30
31def p_expression_binop(t):
32 '''expression : expression PLUS expression
33 | expression MINUS expression
34 | expression TIMES expression
35 | expression DIVIDE expression'''
36 if t[2] == '+' : t[0] = t[1] + t[3]
37 elif t[2] == '-': t[0] = t[1] - t[3]
38 elif t[2] == '*': t[0] = t[1] * t[3]
41 elif t[3] == '/': t[0] = t[1] / t[3]
39 elif t[2] == '/': t[0] = t[1] / t[3]
42
43def p_expression_uminus(t):
44 'expression : MINUS expression %prec UMINUS'
45 t[0] = -t[2]
46
47def p_expression_group(t):
48 'expression : LPAREN expression RPAREN'
49 t[0] = t[2]
50
51def p_expression_number(t):
52 'expression : NUMBER'
53 t[0] = t[1]
54
55def p_expression_name(t):
56 'expression : NAME'
57 try:
58 t[0] = names[t[1]]
59 except LookupError:
40
41def p_expression_uminus(t):
42 'expression : MINUS expression %prec UMINUS'
43 t[0] = -t[2]
44
45def p_expression_group(t):
46 'expression : LPAREN expression RPAREN'
47 t[0] = t[2]
48
49def p_expression_number(t):
50 'expression : NUMBER'
51 t[0] = t[1]
52
53def p_expression_name(t):
54 'expression : NAME'
55 try:
56 t[0] = names[t[1]]
57 except LookupError:
60 print "Undefined name '%s'" % t[1]
58 print("Undefined name '%s'" % t[1])
61 t[0] = 0
62
63def p_error(t):
59 t[0] = 0
60
61def p_error(t):
64 print "Syntax error at '%s'" % t.value
62 print("Syntax error at '%s'" % t.value)
65
66yacc.yacc()
67
68
69
70
63
64yacc.yacc()
65
66
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68