77 lines
2.6 KiB
Scheme
77 lines
2.6 KiB
Scheme
;;; -*-scheme-*-
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;;; Mes --- Maxwell Equations of Software
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;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
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;;;
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;;; let.mes: This file is part of Mes.
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;;;
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;;; Mes is free software; you can redistribute it and/or modify it
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;;; 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 (at
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;;; your option) any later version.
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;;;
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;;; Mes is distributed in the hope that it will be useful, but
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;;; 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 Mes. If not, see <http://www.gnu.org/licenses/>.
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(define-macro (simple-let bindings . rest)
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`(,`(lambda ,(map car bindings) ,@rest)
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,@(map cadr bindings)))
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(define-macro (named-let label bindings . rest)
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`(simple-let ((,label *unspecified*))
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(set! ,label (lambda ,(map car bindings) ,@rest))
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(,label ,@(map cadr bindings))))
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(define-macro (let bindings-or-label . rest)
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`(`,(if ,(symbol? bindings-or-label)
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(list 'lambda '() (cons* 'named-let ,bindings-or-label ,(car rest) ,(cdr rest)))
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(list 'lambda '() (cons* 'simple-let ,bindings-or-label ,rest)))))
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(define-macro (xsimple-let bindings rest)
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`(,`(lambda ,(map car bindings) ,@rest)
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,@(map cadr bindings)))
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(define-macro (xnamed-let label bindings rest)
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`(simple-let ((,label *unspecified*))
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(set! ,label (lambda ,(map car bindings) ,@rest))
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(,label ,@(map cadr bindings))))
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;; IF
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(define-macro (let bindings-or-label . rest)
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`(if ,(symbol? bindings-or-label) ;; IF
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(xnamed-let ,bindings-or-label ,(car rest) ,(cdr rest))
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(xsimple-let ,bindings-or-label ,rest)))
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(define (expand-let* bindings body)
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(if (null? bindings)
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`((lambda () ,@body))
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`((lambda (,(caar bindings))
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,(expand-let* (cdr bindings) body))
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,@(cdar bindings))))
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(define-macro (let* bindings . body)
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(expand-let* bindings body))
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(define (unspecified-bindings bindings params)
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(if (null? bindings) params
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(unspecified-bindings
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(cdr bindings)
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(append params (cons (cons (caar bindings) '(*unspecified*)) '())))))
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(define (letrec-setters bindings setters)
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(if (null? bindings) setters
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(letrec-setters (cdr bindings)
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(append setters
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(cons (cons 'set! (car bindings)) '())))))
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(define-macro (letrec bindings . body)
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`(let ,(unspecified-bindings bindings '())
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,@(letrec-setters bindings '())
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,@body))
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