racket/readline.rkt

   1 #lang racket
   2
   3 (provide readline)
   4
   5 (require (prefix-in readline: readline/readline))
   6
   7 (require "types.rkt")
   8
   9 (define history-loaded #f)
  10 (define HISTORY-FILE (format "~a/.mal-history" (find-system-path 'home-dir)))
  11
  12 (define (load-history path)
  13   (with-handlers
  14     ([exn:fail? (lambda (e) #t)])
  15     (map
  16       (lambda (line) (readline:add-history line))
  17       (string-split
  18         (port->string (open-input-file path))
  19         #px"\n"))))
  20
  21 (define (readline prompt)
  22   (when (not history-loaded)
  23     (set! history-loaded #t)
  24     (load-history HISTORY-FILE))
  25   (let ([line (readline:readline prompt)])
  26     (if (eq? eof line)
  27       nil
  28       (begin
  29         (readline:add-history line)
  30         (with-handlers
  31           ([exn:fail? (lambda (e) #t)])
  32           (with-output-to-file
  33             HISTORY-FILE
  34             (lambda () (printf "~a~n" line))
  35             #:exists 'append))
  36         line))))