75 lines
2.1 KiB
Racket
75 lines
2.1 KiB
Racket
#lang racket
|
|
|
|
;; (C) Copyright Collin J. Doering 2014
|
|
;;
|
|
;; 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 <http://www.gnu.org/licenses/>.
|
|
|
|
;; File: church-booleans.rkt
|
|
;; Author: Collin J. Doering <collin.doering@rekahsoft.ca>
|
|
;; Date: Oct 28, 2014
|
|
|
|
;; Implementation of booleans with only the use of define and lambda
|
|
|
|
(define my-true (lambda (x)
|
|
(lambda (y) x)))
|
|
(define my-false (lambda (x)
|
|
(lambda (y) y)))
|
|
|
|
(define (to-built-in-bool a)
|
|
((a #t) #f))
|
|
|
|
(define (not a)
|
|
(lambda (x)
|
|
(lambda (y)
|
|
((a y) x))))
|
|
|
|
(define (and-op a b)
|
|
(let ([evaled-a (a)])
|
|
((evaled-a (b)) evaled-a)))
|
|
|
|
(define (my-and . xs)
|
|
(foldr and-op my-true xs))
|
|
|
|
(define (or-op a b)
|
|
(let ([evaled-a (a)])
|
|
((evaled-a evaled-a) (b))))
|
|
|
|
(define (my-or . xs)
|
|
(foldr or-op my-false xs))
|
|
|
|
;; (lazy-fun (f x1 ... xn) body) => macro with name "f-lazy" generated which is like the lazy-funcall macro
|
|
;; (lazy-funcall f x1 ... xn) ==> (f (lambda () x1) ... (lambda () xn))
|
|
|
|
;;
|
|
;; Testing the functions
|
|
;;
|
|
|
|
(displayln "Testing and: should output false then #f on the next line indicating and (as well as and-op) did not evaluate its second argument")
|
|
(to-built-in-bool
|
|
(my-and
|
|
(begin (displayln 'false)
|
|
my-false)
|
|
(begin (displayln 'what)
|
|
my-true)))
|
|
|
|
(newline)
|
|
|
|
(displayln "Testing or: should output true then #t on the next line indicating or (and or-op) did not evaluate its second argument")
|
|
(to-built-in-bool
|
|
(my-or
|
|
(begin (displayln 'true)
|
|
my-true)
|
|
(begin (displayln 'what)
|
|
my-false)))
|