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
15if sys.version_info[0] >= 3:
16 raw_input = input
17
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 """
26 tokens = ()
27 precedence = ()
28
29 def __init__(self, **kw):
30 self.debug = kw.get('debug', 0)
31 self.names = { }
32 try:
33 modname = os.path.split(os.path.splitext(__file__)[0])[1] + "_" + self.__class__.__name__
34 except:
35 modname = "parser"+"_"+self.__class__.__name__
36 self.debugfile = modname + ".dbg"
37 self.tabmodule = modname + "_" + "parsetab"
38 #print self.debugfile, self.tabmodule
39
40 # Build the lexer and parser
41 lex.lex(module=self, debug=self.debug)
42 yacc.yacc(module=self,
43 debug=self.debug,
44 debugfile=self.debugfile,
45 tabmodule=self.tabmodule)
46
47 def run(self):
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
56
57class Calc(Parser):
58
59 tokens = (
60 'NAME','NUMBER',
61 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
62 'LPAREN','RPAREN',
63 )
64
65 # Tokens
66
67 t_PLUS = r'\+'
68 t_MINUS = r'-'
69 t_EXP = r'\*\*'
70 t_TIMES = r'\*'
71 t_DIVIDE = r'/'
72 t_EQUALS = r'='
73 t_LPAREN = r'\('
74 t_RPAREN = r'\)'
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:
82 print("Integer value too large %s" % t.value)
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")
92
93 def t_error(self, t):
94 print("Illegal character '%s'" % t.value[0])
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'
112 print(p[1])
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
121 """
122 #print [repr(p[i]) for i in range(0,4)]
123 if p[2] == '+' : p[0] = p[1] + p[3]
124 elif p[2] == '-': p[0] = p[1] - p[3]
125 elif p[2] == '*': p[0] = p[1] * p[3]
126 elif p[2] == '/': p[0] = p[1] / p[3]
127 elif p[2] == '**': p[0] = p[1] ** p[3]
128
129 def p_expression_uminus(self, p):
130 'expression : MINUS expression %prec UMINUS'
131 p[0] = -p[2]
132
133 def p_expression_group(self, p):
134 'expression : LPAREN expression RPAREN'
135 p[0] = p[2]
136
137 def p_expression_number(self, p):
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:
146 print("Undefined name '%s'" % p[1])
147 p[0] = 0
148
149 def p_error(self, p):
150 if p:
151 print("Syntax error at '%s'" % p.value)
152 else:
153 print("Syntax error at EOF")
154
155if __name__ == '__main__':
156 calc = Calc()
157 calc.run()
| 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
15if sys.version_info[0] >= 3:
16 raw_input = input
17
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 """
26 tokens = ()
27 precedence = ()
28
29 def __init__(self, **kw):
30 self.debug = kw.get('debug', 0)
31 self.names = { }
32 try:
33 modname = os.path.split(os.path.splitext(__file__)[0])[1] + "_" + self.__class__.__name__
34 except:
35 modname = "parser"+"_"+self.__class__.__name__
36 self.debugfile = modname + ".dbg"
37 self.tabmodule = modname + "_" + "parsetab"
38 #print self.debugfile, self.tabmodule
39
40 # Build the lexer and parser
41 lex.lex(module=self, debug=self.debug)
42 yacc.yacc(module=self,
43 debug=self.debug,
44 debugfile=self.debugfile,
45 tabmodule=self.tabmodule)
46
47 def run(self):
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
56
57class Calc(Parser):
58
59 tokens = (
60 'NAME','NUMBER',
61 'PLUS','MINUS','EXP', 'TIMES','DIVIDE','EQUALS',
62 'LPAREN','RPAREN',
63 )
64
65 # Tokens
66
67 t_PLUS = r'\+'
68 t_MINUS = r'-'
69 t_EXP = r'\*\*'
70 t_TIMES = r'\*'
71 t_DIVIDE = r'/'
72 t_EQUALS = r'='
73 t_LPAREN = r'\('
74 t_RPAREN = r'\)'
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:
82 print("Integer value too large %s" % t.value)
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")
92
93 def t_error(self, t):
94 print("Illegal character '%s'" % t.value[0])
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'
112 print(p[1])
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
121 """
122 #print [repr(p[i]) for i in range(0,4)]
123 if p[2] == '+' : p[0] = p[1] + p[3]
124 elif p[2] == '-': p[0] = p[1] - p[3]
125 elif p[2] == '*': p[0] = p[1] * p[3]
126 elif p[2] == '/': p[0] = p[1] / p[3]
127 elif p[2] == '**': p[0] = p[1] ** p[3]
128
129 def p_expression_uminus(self, p):
130 'expression : MINUS expression %prec UMINUS'
131 p[0] = -p[2]
132
133 def p_expression_group(self, p):
134 'expression : LPAREN expression RPAREN'
135 p[0] = p[2]
136
137 def p_expression_number(self, p):
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:
146 print("Undefined name '%s'" % p[1])
147 p[0] = 0
148
149 def p_error(self, p):
150 if p:
151 print("Syntax error at '%s'" % p.value)
152 else:
153 print("Syntax error at EOF")
154
155if __name__ == '__main__':
156 calc = Calc()
157 calc.run()
|