yacc_notfunc.py revision 2632:1bb2f91485ea 
1# -----------------------------------------------------------------------------
2# yacc_notfunc.py
3#
4# p_rule not defined as a function
5# -----------------------------------------------------------------------------
6import sys
7sys.tracebacklimit = 0
8
9from calclex import tokens
10
11# Parsing rules
12precedence = (
13    ('left','PLUS','MINUS'),
14    ('left','TIMES','DIVIDE'),
15    ('right','UMINUS'),
16    )
17
18# dictionary of names
19names = { }
20
21p_statement_assign = "Blah"
22
23def p_statement_expr(t):
24    'statement : expression'
25    print t[1]
26
27def p_expression_binop(t):
28    '''expression : expression PLUS expression
29                  | expression MINUS expression
30                  | expression TIMES expression
31                  | expression DIVIDE expression'''
32    if t[2] == '+'  : t[0] = t[1] + t[3]
33    elif t[2] == '-': t[0] = t[1] - t[3]
34    elif t[2] == '*': t[0] = t[1] * t[3]
35    elif t[3] == '/': t[0] = t[1] / t[3]
36
37def p_expression_uminus(t):
38    'expression : MINUS expression %prec UMINUS'
39    t[0] = -t[2]
40
41def p_expression_group(t):
42    'expression : LPAREN expression RPAREN'
43    t[0] = t[2]
44
45def p_expression_number(t):
46    'expression : NUMBER'
47    t[0] = t[1]
48
49def p_expression_name(t):
50    'expression : NAME'
51    try:
52        t[0] = names[t[1]]
53    except LookupError:
54        print "Undefined name '%s'" % t[1]
55        t[0] = 0
56
57def p_error(t):
58    print "Syntax error at '%s'" % t.value
59
60import yacc
61yacc.yacc()
62
63
64
65
66