calc.py (4479:61d3ed46e373) calc.py (6498:e21e9ab5fad0)
1# -----------------------------------------------------------------------------
2# calc.py
3#
4# A simple calculator with variables. This is from O'Reilly's
5# "Lex and Yacc", p. 63.
6# -----------------------------------------------------------------------------
7
8import sys
9sys.path.insert(0,"../..")
10
1# -----------------------------------------------------------------------------
2# calc.py
3#
4# A simple calculator with variables. This is from O'Reilly's
5# "Lex and Yacc", p. 63.
6# -----------------------------------------------------------------------------
7
8import sys
9sys.path.insert(0,"../..")
10
11if sys.version_info[0] >= 3:
12 raw_input = input
13
11tokens = (
12 'NAME','NUMBER',
13 )
14
15literals = ['=','+','-','*','/', '(',')']
16
17# Tokens
18
19t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
20
21def t_NUMBER(t):
22 r'\d+'
14tokens = (
15 'NAME','NUMBER',
16 )
17
18literals = ['=','+','-','*','/', '(',')']
19
20# Tokens
21
22t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
23
24def t_NUMBER(t):
25 r'\d+'
23 try:
24 t.value = int(t.value)
25 except ValueError:
26 print "Integer value too large", t.value
27 t.value = 0
26 t.value = int(t.value)
28 return t
29
30t_ignore = " \t"
31
32def t_newline(t):
33 r'\n+'
34 t.lexer.lineno += t.value.count("\n")
27 return t
28
29t_ignore = " \t"
30
31def t_newline(t):
32 r'\n+'
33 t.lexer.lineno += t.value.count("\n")
35
34
36def t_error(t):
35def t_error(t):
37 print "Illegal character '%s'" % t.value[0]
36 print("Illegal character '%s'" % t.value[0])
38 t.lexer.skip(1)
37 t.lexer.skip(1)
39
38
40# Build the lexer
41import ply.lex as lex
42lex.lex()
43
44# Parsing rules
45
46precedence = (
47 ('left','+','-'),

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

53names = { }
54
55def p_statement_assign(p):
56 'statement : NAME "=" expression'
57 names[p[1]] = p[3]
58
59def p_statement_expr(p):
60 'statement : expression'
39# Build the lexer
40import ply.lex as lex
41lex.lex()
42
43# Parsing rules
44
45precedence = (
46 ('left','+','-'),

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

52names = { }
53
54def p_statement_assign(p):
55 'statement : NAME "=" expression'
56 names[p[1]] = p[3]
57
58def p_statement_expr(p):
59 'statement : expression'
61 print p[1]
60 print(p[1])
62
63def p_expression_binop(p):
64 '''expression : expression '+' expression
65 | expression '-' expression
66 | expression '*' expression
67 | expression '/' expression'''
68 if p[2] == '+' : p[0] = p[1] + p[3]
69 elif p[2] == '-': p[0] = p[1] - p[3]

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

82 "expression : NUMBER"
83 p[0] = p[1]
84
85def p_expression_name(p):
86 "expression : NAME"
87 try:
88 p[0] = names[p[1]]
89 except LookupError:
61
62def p_expression_binop(p):
63 '''expression : expression '+' expression
64 | expression '-' expression
65 | expression '*' expression
66 | expression '/' expression'''
67 if p[2] == '+' : p[0] = p[1] + p[3]
68 elif p[2] == '-': p[0] = p[1] - p[3]

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

81 "expression : NUMBER"
82 p[0] = p[1]
83
84def p_expression_name(p):
85 "expression : NAME"
86 try:
87 p[0] = names[p[1]]
88 except LookupError:
90 print "Undefined name '%s'" % p[1]
89 print("Undefined name '%s'" % p[1])
91 p[0] = 0
92
93def p_error(p):
90 p[0] = 0
91
92def p_error(p):
94 print "Syntax error at '%s'" % p.value
93 if p:
94 print("Syntax error at '%s'" % p.value)
95 else:
96 print("Syntax error at EOF")
95
96import ply.yacc as yacc
97yacc.yacc()
98
99while 1:
100 try:
101 s = raw_input('calc > ')
102 except EOFError:
103 break
104 if not s: continue
105 yacc.parse(s)
97
98import ply.yacc as yacc
99yacc.yacc()
100
101while 1:
102 try:
103 s = raw_input('calc > ')
104 except EOFError:
105 break
106 if not s: continue
107 yacc.parse(s)