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| 1 # ----------------------------------------------------------------------------- |
| 2 # lex_object.py |
| 3 # ----------------------------------------------------------------------------- |
| 4 import sys |
| 5 |
| 6 if ".." not in sys.path: sys.path.insert(0,"..") |
| 7 import ply.lex as lex |
| 8 |
| 9 class CalcLexer: |
| 10 tokens = ( |
| 11 'NAME','NUMBER', |
| 12 'PLUS','MINUS','TIMES','DIVIDE','EQUALS', |
| 13 'LPAREN','RPAREN', |
| 14 ) |
| 15 |
| 16 # Tokens |
| 17 |
| 18 t_PLUS = r'\+' |
| 19 t_MINUS = r'-' |
| 20 t_TIMES = r'\*' |
| 21 t_DIVIDE = r'/' |
| 22 t_EQUALS = r'=' |
| 23 t_LPAREN = r'\(' |
| 24 t_RPAREN = r'\)' |
| 25 t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*' |
| 26 |
| 27 def t_NUMBER(self,t): |
| 28 r'\d+' |
| 29 try: |
| 30 t.value = int(t.value) |
| 31 except ValueError: |
| 32 print("Integer value too large %s" % t.value) |
| 33 t.value = 0 |
| 34 return t |
| 35 |
| 36 t_ignore = " \t" |
| 37 |
| 38 def t_newline(self,t): |
| 39 r'\n+' |
| 40 t.lineno += t.value.count("\n") |
| 41 |
| 42 def t_error(self,t): |
| 43 print("Illegal character '%s'" % t.value[0]) |
| 44 t.lexer.skip(1) |
| 45 |
| 46 |
| 47 calc = CalcLexer() |
| 48 |
| 49 # Build the lexer |
| 50 lex.lex(object=calc) |
| 51 lex.runmain(data="3+4") |
| 52 |
| 53 |
| 54 |
| 55 |
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