condx.rkt

;; condx: cond(itionals) with optional eXecution of statements before
					

; This file is part of Scheme+

;; Copyright 2021-2024 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/>.



(module condx racket/base

  (provide condx
	   condx-begin)

 
	  
; example:
;(define x 1)
;(condx ((= x 7) 'never)
;        (exec
;          (define y 3)
;          (set! x 7))
;        ((= y 1) 'definitely_not)
;        (exec
;          (set! y 10)
;          (define z 2))
;        ((= x 7) (+ x y z))
;        (else 'you_should_not_be_here))
;
; 19

(define-syntax condx
  (syntax-rules (exec else)
    ((_) '()) ;; allow no else clause
    ((_ (else e ...))
     (let () e ...))
    ((_ (exec s ...) d1 ...)
     (let () s ... (condx d1 ...)))
    ((_ (t e ...) tail ...)
     (if t
         (let () e ...)
         (condx tail ...)))))

;; (define-syntax condx
;;  (syntax-rules (exec else)
;;    ((_)
 ;;     (error 'condx "No else clause"))
;;    ((_ (else e ...))
;;     (let () e ...))
;;    ((_ (exec s ...) d1 ...)
;;     (let () s ... (condx d1 ...)))
;;    ((_ (t e ...) tail ...)
;;     (if t
;;         (let () e ...)
;;         (condx tail ...)))))

;; warning this ones can not use inner definitions
(define-syntax condx-begin
  (syntax-rules (exec else)
    ((_) '()) ;; allow no else clause
    ((_ (else e ...))
     (begin e ...))
    ((_ (exec s ...) d1 ...)
     (begin s ... (condx-begin d1 ...)))
    ((_ (t e ...) tail ...)
     (if t
         (begin e ...)
         (condx-begin tail ...)))))


;; (define-syntax condx-begin
;;   (syntax-rules (exec else)
;;     ((_)
;;      (error 'condx-begin "No else clause"))
;;     ((_ (else e ...))
;;      (begin e ...))
;;     ((_ (exec s ...) d1 ...)
;;      (begin s ... (condx-begin d1 ...)))
;;     ((_ (t e ...) tail ...)
;;      (if t
;;          (begin e ...)
;;          (condx-begin tail ...)))))


;; (define x 1)
;; (condx ((= x 7) 'never)
;;         (exec
;;           (define y 3)
;;           (set! x 7))
;;         ((= y 1) 'definitely_not)
;;         (exec
;;           (set! y 10)
;;           (define z 2))
;;         ((= x 7) (+ x y z))
;;         (else 'you_should_not_be_here))

;; (define y 0)
;; (define z 0)
;; (set! x 1)
;; (condx-begin ((= x 7) 'never)
;;         (exec
;;           (set! y 3)
;;           (set! x 7))
;;         ((= y 1) 'definitely_not)
;;         (exec
;;           (set! y 10)
;;           (set! z 2))
;;         ((= x 7) (+ x y z))
;;         (else 'you_should_not_be_here))

) ; end library