mes/let.mes

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;;; -*-scheme-*-
;;; Mes --- Maxwell Equations of Software
;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
;;;
;;; test.mes: This file is part of Mes.
;;;
;;; Mes 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.
;;;
;;; Mes 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 Mes. If not, see <http://www.gnu.org/licenses/>.
(define-macro (simple-let bindings . rest)
`(,`(lambda ,(map car bindings) ,@rest)
,@(map cadr bindings)))
(define-macro (named-let label bindings . rest)
`(simple-let ((,label *unspecified*))
(set! ,label (lambda ,(map car bindings) ,@rest))
(,label ,@(map cadr bindings))))
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(define-macro (let bindings-or-label . rest)
`(`,(cond (,(symbol? bindings-or-label)
(list 'lambda '() (cons* 'named-let ,bindings-or-label ,(car rest) ,(cdr rest))))
(#t
(list 'lambda '() (cons* 'simple-let ,bindings-or-label ,rest))))))
(define-macro (xsimple-let bindings rest)
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`(,`(lambda ,(map car bindings) ,@rest)
,@(map cadr bindings)))
(define-macro (xnamed-let label bindings rest)
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`(simple-let ((,label *unspecified*))
(set! ,label (lambda ,(map car bindings) ,@rest))
(,label ,@(map cadr bindings))))
(define-macro (let bindings-or-label . rest)
`(cond (,(symbol? bindings-or-label)
(xnamed-let ,bindings-or-label ,(car rest) ,(cdr rest)))
(#t (xsimple-let ,bindings-or-label ,rest))))
(define (expand-let* bindings body)
(cond ((null? bindings)
`((lambda () ,@body)))
(#t `((lambda (,(caar bindings))
,(expand-let* (cdr bindings) body))
,@(cdar bindings)))))
(define-macro (let* bindings . body)
(expand-let* bindings body))
(define (unspecified-bindings bindings params)
(cond ((null? bindings) params)
(#t (unspecified-bindings
(cdr bindings)
(append params (cons (cons (caar bindings) '(*unspecified*)) '()))))))
(define (letrec-setters bindings setters)
(cond ((null? bindings) setters)
(#t (letrec-setters (cdr bindings)
(append setters
(cons (cons 'set! (car bindings)) '()))))))
(define-macro (letrec bindings . body)
`(let ,(unspecified-bindings bindings '())
,@(letrec-setters bindings '())
,@body))