common-lisp/step0_repl.lisp

   1 (defpackage :mal
   2   (:use :common-lisp
   3         :uiop)
   4   (:export :main))
   5
   6 (in-package :mal)
   7
   8 (defun mal-read (string)
   9   string)
  10
  11 (defun mal-eval (ast)
  12   ast)
  13
  14 (defun mal-print (expression)
  15   expression)
  16
  17 (defun rep (string)
  18   (mal-print (mal-eval (mal-read string))))
  19
  20 (defvar *use-readline-p* nil)
  21
  22 (defun raw-input (prompt)
  23   (format *standard-output* prompt)
  24   (force-output *standard-output*)
  25   (read-line *standard-input* nil))
  26
  27 (defun mal-readline (prompt)
  28   (if *use-readline-p*
  29       (cl-readline:readline :prompt prompt
  30                             :add-history t
  31                             :novelty-check (lambda (old new)
  32                                              (not (string= old new))))
  33       (raw-input prompt)))
  34
  35 (defun mal-writeline (string)
  36   (when string
  37     (write-line string)
  38     (force-output *standard-output*)))
  39
  40 (defun main (&optional (argv nil argv-provided-p))
  41   (declare (ignorable argv argv-provided-p))
  42   (setf *use-readline-p* (not (or (string= (uiop:getenv "PERL_RL") "false")
  43                                   (string= (uiop:getenv "TERM") "dumb"))))
  44   (loop do (let ((line (mal-readline "user> ")))
  45              (if line (mal-writeline (rep line)) (return)))))