ext/ply/example/BASIC/basiclex.py

   1 # An implementation of Dartmouth BASIC (1964)
   2
   3 from ply import *
   4
   5 keywords = (
   6     'LET','READ','DATA','PRINT','GOTO','IF','THEN','FOR','NEXT','TO','STEP',
   7     'END','STOP','DEF','GOSUB','DIM','REM','RETURN','RUN','LIST','NEW',
   8 )
   9
  10 tokens = keywords + (
  11      'EQUALS','PLUS','MINUS','TIMES','DIVIDE','POWER',
  12      'LPAREN','RPAREN','LT','LE','GT','GE','NE',
  13      'COMMA','SEMI', 'INTEGER','FLOAT', 'STRING',
  14      'ID','NEWLINE'
  15 )
  16
  17 t_ignore = ' \t'
  18
  19 def t_REM(t):
  20     r'REM .*'
  21     return t
  22
  23 def t_ID(t):
  24     r'[A-Z][A-Z0-9]*'
  25     if t.value in keywords:
  26         t.type = t.value
  27     return t
  28
  29 t_EQUALS  = r'='
  30 t_PLUS    = r'\+'
  31 t_MINUS   = r'-'
  32 t_TIMES   = r'\*'
  33 t_POWER   = r'\^'
  34 t_DIVIDE  = r'/'
  35 t_LPAREN  = r'\('
  36 t_RPAREN  = r'\)'
  37 t_LT      = r'<'
  38 t_LE      = r'<='
  39 t_GT      = r'>'
  40 t_GE      = r'>='
  41 t_NE      = r'<>'
  42 t_COMMA   = r'\,'
  43 t_SEMI    = r';'
  44 t_INTEGER = r'\d+'
  45 t_FLOAT   = r'((\d*\.\d+)(E[\+-]?\d+)?|([1-9]\d*E[\+-]?\d+))'
  46 t_STRING  = r'\".*?\"'
  47
  48 def t_NEWLINE(t):
  49     r'\n'
  50     t.lexer.lineno += 1
  51     return t
  52
  53 def t_error(t):
  54     print "Illegal character", t.value[0]
  55     t.lexer.skip(1)
  56
  57 lex.lex()
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74