repeat-until.scm

; This file is part of Scheme+

;; Copyright 2021-2022 Damien MATTEI

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.


;; scheme@(guile-user)> (define i 5)
;; scheme@(guile-user)> (repeat (display i) (newline) (set! i (- i 1)) until (< i 0))
;; 5
;; 4
;; 3
;; 2
;; 1
;; 0

(define-syntax repeat
  (syntax-rules (until)
    ((repeat b1 ...
       until pred)
     (let loop () b1 ... (when (not pred) (loop))))))