calc.py (4479:61d3ed46e373) | calc.py (6498:e21e9ab5fad0) |
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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 |
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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) |