calc.py (4479:61d3ed46e373) calc.py (6498:e21e9ab5fad0)
1#!/usr/bin/env python
2
3# -----------------------------------------------------------------------------
4# calc.py
5#
6# A simple calculator with variables. This is from O'Reilly's
7# "Lex and Yacc", p. 63.
8#
9# Class-based example contributed to PLY by David McNab
10# -----------------------------------------------------------------------------
11
12import sys
13sys.path.insert(0,"../..")
14
1#!/usr/bin/env python
2
3# -----------------------------------------------------------------------------
4# calc.py
5#
6# A simple calculator with variables. This is from O'Reilly's
7# "Lex and Yacc", p. 63.
8#
9# Class-based example contributed to PLY by David McNab
10# -----------------------------------------------------------------------------
11
12import sys
13sys.path.insert(0,"../..")
14
15import readline
15if sys.version_info[0] >= 3:
16 raw_input = input
17
16import ply.lex as lex
17import ply.yacc as yacc
18import os
19
20class Parser:
21 """
22 Base class for a lexer/parser that has the rules defined as methods
23 """

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

46 while 1:
47 try:
48 s = raw_input('calc > ')
49 except EOFError:
50 break
51 if not s: continue
52 yacc.parse(s)
53
18import ply.lex as lex
19import ply.yacc as yacc
20import os
21
22class Parser:
23 """
24 Base class for a lexer/parser that has the rules defined as methods
25 """

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

48 while 1:
49 try:
50 s = raw_input('calc > ')
51 except EOFError:
52 break
53 if not s: continue
54 yacc.parse(s)
55
54
56
55class Calc(Parser):
56
57 tokens = (
58 'NAME','NUMBER',
59 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
60 'LPAREN','RPAREN',
61 )
62

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72 t_RPAREN = r'\)'
73 t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
74
75 def t_NUMBER(self, t):
76 r'\d+'
77 try:
78 t.value = int(t.value)
79 except ValueError:
57class Calc(Parser):
58
59 tokens = (
60 'NAME','NUMBER',
61 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
62 'LPAREN','RPAREN',
63 )
64

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74 t_RPAREN = r'\)'
75 t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
76
77 def t_NUMBER(self, t):
78 r'\d+'
79 try:
80 t.value = int(t.value)
81 except ValueError:
80 print "Integer value too large", t.value
82 print("Integer value too large %s" % t.value)
81 t.value = 0
82 #print "parsed number %s" % repr(t.value)
83 return t
84
85 t_ignore = " \t"
86
87 def t_newline(self, t):
88 r'\n+'
89 t.lexer.lineno += t.value.count("\n")
83 t.value = 0
84 #print "parsed number %s" % repr(t.value)
85 return t
86
87 t_ignore = " \t"
88
89 def t_newline(self, t):
90 r'\n+'
91 t.lexer.lineno += t.value.count("\n")
90
92
91 def t_error(self, t):
93 def t_error(self, t):
92 print "Illegal character '%s'" % t.value[0]
94 print("Illegal character '%s'" % t.value[0])
93 t.lexer.skip(1)
94
95 # Parsing rules
96
97 precedence = (
98 ('left','PLUS','MINUS'),
99 ('left','TIMES','DIVIDE'),
100 ('left', 'EXP'),
101 ('right','UMINUS'),
102 )
103
104 def p_statement_assign(self, p):
105 'statement : NAME EQUALS expression'
106 self.names[p[1]] = p[3]
107
108 def p_statement_expr(self, p):
109 'statement : expression'
95 t.lexer.skip(1)
96
97 # Parsing rules
98
99 precedence = (
100 ('left','PLUS','MINUS'),
101 ('left','TIMES','DIVIDE'),
102 ('left', 'EXP'),
103 ('right','UMINUS'),
104 )
105
106 def p_statement_assign(self, p):
107 'statement : NAME EQUALS expression'
108 self.names[p[1]] = p[3]
109
110 def p_statement_expr(self, p):
111 'statement : expression'
110 print p[1]
112 print(p[1])
111
112 def p_expression_binop(self, p):
113 """
114 expression : expression PLUS expression
115 | expression MINUS expression
116 | expression TIMES expression
117 | expression DIVIDE expression
118 | expression EXP expression

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136 'expression : NUMBER'
137 p[0] = p[1]
138
139 def p_expression_name(self, p):
140 'expression : NAME'
141 try:
142 p[0] = self.names[p[1]]
143 except LookupError:
113
114 def p_expression_binop(self, p):
115 """
116 expression : expression PLUS expression
117 | expression MINUS expression
118 | expression TIMES expression
119 | expression DIVIDE expression
120 | expression EXP expression

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138 'expression : NUMBER'
139 p[0] = p[1]
140
141 def p_expression_name(self, p):
142 'expression : NAME'
143 try:
144 p[0] = self.names[p[1]]
145 except LookupError:
144 print "Undefined name '%s'" % p[1]
146 print("Undefined name '%s'" % p[1])
145 p[0] = 0
146
147 def p_error(self, p):
147 p[0] = 0
148
149 def p_error(self, p):
148 print "Syntax error at '%s'" % p.value
150 if p:
151 print("Syntax error at '%s'" % p.value)
152 else:
153 print("Syntax error at EOF")
149
150if __name__ == '__main__':
151 calc = Calc()
152 calc.run()
154
155if __name__ == '__main__':
156 calc = Calc()
157 calc.run()