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