7267
|
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 # Modified to use new-style classes. Test case.
|
|
12 # -----------------------------------------------------------------------------
|
|
13
|
|
14 import sys
|
|
15 sys.path.insert(0,"../..")
|
|
16
|
|
17 if sys.version_info[0] >= 3:
|
|
18 raw_input = input
|
|
19
|
|
20 import ply.lex as lex
|
|
21 import ply.yacc as yacc
|
|
22 import os
|
|
23
|
|
24 class Parser(object):
|
|
25 """
|
|
26 Base class for a lexer/parser that has the rules defined as methods
|
|
27 """
|
|
28 tokens = ()
|
|
29 precedence = ()
|
|
30
|
|
31
|
|
32 def __init__(self, **kw):
|
|
33 self.debug = kw.get('debug', 0)
|
|
34 self.names = { }
|
|
35 try:
|
|
36 modname = os.path.split(os.path.splitext(__file__)[0])[1] + "_" + self.__class__.__name__
|
|
37 except:
|
|
38 modname = "parser"+"_"+self.__class__.__name__
|
|
39 self.debugfile = modname + ".dbg"
|
|
40 self.tabmodule = modname + "_" + "parsetab"
|
|
41 #print self.debugfile, self.tabmodule
|
|
42
|
|
43 # Build the lexer and parser
|
|
44 lex.lex(module=self, debug=self.debug)
|
|
45 yacc.yacc(module=self,
|
|
46 debug=self.debug,
|
|
47 debugfile=self.debugfile,
|
|
48 tabmodule=self.tabmodule)
|
|
49
|
|
50 def run(self):
|
|
51 while 1:
|
|
52 try:
|
|
53 s = raw_input('calc > ')
|
|
54 except EOFError:
|
|
55 break
|
|
56 if not s: continue
|
|
57 yacc.parse(s)
|
|
58
|
|
59
|
|
60 class Calc(Parser):
|
|
61
|
|
62 tokens = (
|
|
63 'NAME','NUMBER',
|
|
64 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
|
|
65 'LPAREN','RPAREN',
|
|
66 )
|
|
67
|
|
68 # Tokens
|
|
69
|
|
70 t_PLUS = r'\+'
|
|
71 t_MINUS = r'-'
|
|
72 t_EXP = r'\*\*'
|
|
73 t_TIMES = r'\*'
|
|
74 t_DIVIDE = r'/'
|
|
75 t_EQUALS = r'='
|
|
76 t_LPAREN = r'\('
|
|
77 t_RPAREN = r'\)'
|
|
78 t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
|
|
79
|
|
80 def t_NUMBER(self, t):
|
|
81 r'\d+'
|
|
82 try:
|
|
83 t.value = int(t.value)
|
|
84 except ValueError:
|
|
85 print("Integer value too large %s" % t.value)
|
|
86 t.value = 0
|
|
87 #print "parsed number %s" % repr(t.value)
|
|
88 return t
|
|
89
|
|
90 t_ignore = " \t"
|
|
91
|
|
92 def t_newline(self, t):
|
|
93 r'\n+'
|
|
94 t.lexer.lineno += t.value.count("\n")
|
|
95
|
|
96 def t_error(self, t):
|
|
97 print("Illegal character '%s'" % t.value[0])
|
|
98 t.lexer.skip(1)
|
|
99
|
|
100 # Parsing rules
|
|
101
|
|
102 precedence = (
|
|
103 ('left','PLUS','MINUS'),
|
|
104 ('left','TIMES','DIVIDE'),
|
|
105 ('left', 'EXP'),
|
|
106 ('right','UMINUS'),
|
|
107 )
|
|
108
|
|
109 def p_statement_assign(self, p):
|
|
110 'statement : NAME EQUALS expression'
|
|
111 self.names[p[1]] = p[3]
|
|
112
|
|
113 def p_statement_expr(self, p):
|
|
114 'statement : expression'
|
|
115 print(p[1])
|
|
116
|
|
117 def p_expression_binop(self, p):
|
|
118 """
|
|
119 expression : expression PLUS expression
|
|
120 | expression MINUS expression
|
|
121 | expression TIMES expression
|
|
122 | expression DIVIDE expression
|
|
123 | expression EXP expression
|
|
124 """
|
|
125 #print [repr(p[i]) for i in range(0,4)]
|
|
126 if p[2] == '+' : p[0] = p[1] + p[3]
|
|
127 elif p[2] == '-': p[0] = p[1] - p[3]
|
|
128 elif p[2] == '*': p[0] = p[1] * p[3]
|
|
129 elif p[2] == '/': p[0] = p[1] / p[3]
|
|
130 elif p[2] == '**': p[0] = p[1] ** p[3]
|
|
131
|
|
132 def p_expression_uminus(self, p):
|
|
133 'expression : MINUS expression %prec UMINUS'
|
|
134 p[0] = -p[2]
|
|
135
|
|
136 def p_expression_group(self, p):
|
|
137 'expression : LPAREN expression RPAREN'
|
|
138 p[0] = p[2]
|
|
139
|
|
140 def p_expression_number(self, p):
|
|
141 'expression : NUMBER'
|
|
142 p[0] = p[1]
|
|
143
|
|
144 def p_expression_name(self, p):
|
|
145 'expression : NAME'
|
|
146 try:
|
|
147 p[0] = self.names[p[1]]
|
|
148 except LookupError:
|
|
149 print("Undefined name '%s'" % p[1])
|
|
150 p[0] = 0
|
|
151
|
|
152 def p_error(self, p):
|
|
153 if p:
|
|
154 print("Syntax error at '%s'" % p.value)
|
|
155 else:
|
|
156 print("Syntax error at EOF")
|
|
157
|
|
158 if __name__ == '__main__':
|
|
159 calc = Calc()
|
|
160 calc.run()
|