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7267
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1 # An implementation of Dartmouth BASIC (1964)
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2
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3 from ply import *
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4
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5 keywords = (
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6 'LET','READ','DATA','PRINT','GOTO','IF','THEN','FOR','NEXT','TO','STEP',
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7 'END','STOP','DEF','GOSUB','DIM','REM','RETURN','RUN','LIST','NEW',
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8 )
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9
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10 tokens = keywords + (
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11 'EQUALS','PLUS','MINUS','TIMES','DIVIDE','POWER',
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12 'LPAREN','RPAREN','LT','LE','GT','GE','NE',
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13 'COMMA','SEMI', 'INTEGER','FLOAT', 'STRING',
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14 'ID','NEWLINE'
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15 )
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16
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17 t_ignore = ' \t'
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18
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19 def t_REM(t):
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20 r'REM .*'
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21 return t
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22
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23 def t_ID(t):
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24 r'[A-Z][A-Z0-9]*'
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25 if t.value in keywords:
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26 t.type = t.value
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27 return t
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28
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29 t_EQUALS = r'='
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30 t_PLUS = r'\+'
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31 t_MINUS = r'-'
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32 t_TIMES = r'\*'
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33 t_POWER = r'\^'
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34 t_DIVIDE = r'/'
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35 t_LPAREN = r'\('
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36 t_RPAREN = r'\)'
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37 t_LT = r'<'
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38 t_LE = r'<='
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39 t_GT = r'>'
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40 t_GE = r'>='
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41 t_NE = r'<>'
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42 t_COMMA = r'\,'
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43 t_SEMI = r';'
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44 t_INTEGER = r'\d+'
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45 t_FLOAT = r'((\d*\.\d+)(E[\+-]?\d+)?|([1-9]\d*E[\+-]?\d+))'
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46 t_STRING = r'\".*?\"'
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47
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48 def t_NEWLINE(t):
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49 r'\n'
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50 t.lexer.lineno += 1
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51 return t
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52
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53 def t_error(t):
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54 print("Illegal character %s" % t.value[0])
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55 t.lexer.skip(1)
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56
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57 lex.lex(debug=0)
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58
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59
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60
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61
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62
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63
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64
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65
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66
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67
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68
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69
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70
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72
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74
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