You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
beautiful-racket/beautiful-racket-demo/basic-demo-3/lexer.rkt

26 lines
1.0 KiB
Racket

8 years ago
#lang br
(require brag/support)
(define-lex-abbrev digits (:+ (char-set "0123456789")))
8 years ago
(define-lex-abbrev reserved-terms (:or "print" "goto" "end" "+" ":" ";" "let" "=" "input" "-" "*" "/" "^" "mod" "(" ")" "def" "if" "then" "else" "<" ">" "<>" "and" "or" "not" "gosub" "return" "for" "to" "step" "next" "def" "," "import"))
8 years ago
8 years ago
(define basic-lexer
(lexer-srcloc
[(eof) (return-without-srcloc eof)]
["\n" (token 'NEWLINE lexeme)]
[whitespace (token lexeme #:skip? #t)]
[(from/stop-before "rem" "\n") (token 'REM lexeme)]
8 years ago
[reserved-terms (token lexeme lexeme)]
[(:seq alphabetic (:* (:or alphabetic numeric "$" "/" "-" "?")))
8 years ago
(token 'ID (string->symbol lexeme))]
8 years ago
[digits (token 'INTEGER (string->number lexeme))]
[(:or (:seq (:? digits) "." digits)
(:seq digits "."))
(token 'DECIMAL (string->number lexeme))]
[(:or (from/to "\"" "\"") (from/to "'" "'"))
(token 'STRING
(substring lexeme
1 (sub1 (string-length lexeme))))]))
(provide basic-lexer)