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