basiclex.py - mozsearch

Enable keyboard shortcuts

# An implementation of Dartmouth BASIC (1964)

from ply import *

keywords = (

    'LET', 'READ', 'DATA', 'PRINT', 'GOTO', 'IF', 'THEN', 'FOR', 'NEXT', 'TO', 'STEP',

    'END', 'STOP', 'DEF', 'GOSUB', 'DIM', 'REM', 'RETURN', 'RUN', 'LIST', 'NEW',

tokens = keywords + (

    'EQUALS', 'PLUS', 'MINUS', 'TIMES', 'DIVIDE', 'POWER',

    'LPAREN', 'RPAREN', 'LT', 'LE', 'GT', 'GE', 'NE',

    'COMMA', 'SEMI', 'INTEGER', 'FLOAT', 'STRING',

    'ID', 'NEWLINE'

t_ignore = ' \t'

def t_REM(t):

    r'REM .*'

    return t

def t_ID(t):

    r'[A-Z][A-Z0-9]*'

    if t.value in keywords:

        t.type = t.value

    return t

t_EQUALS = r'='

t_PLUS = r'\+'

t_MINUS = r'-'

t_TIMES = r'\*'

t_POWER = r'\^'

t_DIVIDE = r'/'

t_LPAREN = r'\('

t_RPAREN = r'\)'

t_LT = r'<'

t_LE = r'<='

t_GT = r'>'

t_GE = r'>='

t_NE = r'<>'

t_COMMA = r'\,'

t_SEMI = r';'

t_INTEGER = r'\d+'

t_FLOAT = r'((\d*\.\d+)(E[\+-]?\d+)?|([1-9]\d*E[\+-]?\d+))'

t_STRING = r'\".*?\"'

def t_NEWLINE(t):

    r'\n'

    t.lexer.lineno += 1

    return t

def t_error(t):

    print("Illegal character %s" % t.value[0])

    t.lexer.skip(1)

lex.lex(debug=0)