| # 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) |
