58 lines
2.0 KiB
Racket
58 lines
2.0 KiB
Racket
#lang racket
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;; (C) Copyright Collin J. Doering 2014
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;;
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;; This program is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;;
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;;
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;; File: macros.rkt
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;; Author: Collin J. Doering <collin.doering@rekahsoft.ca>
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;; Date: Aug 28, 2014
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;; Description: various implementions of macros for learning purposes
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(require (for-syntax syntax/parse))
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(define-syntax my-while
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(syntax-rules ()
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[(my-while n body ...)
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(if (and (integer? n) (>= n 0))
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(letrec ([f (lambda () body ...)]
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[g (lambda (i)
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(cond [(= i 0) (f)]
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[else (begin
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(f)
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(g (- i 1)))]))])
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(g n))
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(error"Must be a positive integer"))]))
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(define-syntax mylet
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(syntax-rules ()
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[(mylet ([var rhs] ...) body ...) ((lambda (var ...) body ...) rhs ...)]))
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(define-syntax (mylet2 stx)
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(syntax-parse stx
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[(_ ((var:id rhs:expr) ...) body ...+) #'((lambda (var ...) body ...) rhs ...)]))
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(define-syntax (mycond stx)
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(syntax-parse stx #:datum-literals (else)
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[(_) #'(void)]
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[(_ (else en:expr)) #'en]
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[(_ (p e:expr) (p1 e1:expr) ...) #'(if p e (mycond (p1 e1) ...))]))
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;; (module+ test
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;; (test-suite "mycond macro"
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;; (test-case "mycond basecase"
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;; (check-true (void? (mycond)) "mycond when called with no arguments should return void")
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;; (check-eq (mycond [else 'val]) 'val ""))
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;; (test-case "mycond else")))
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