a8b16ba013
* module/mes/catch.mes: New file. * tests/catch.test: New file. * GNUmakefile (TEST): Add it.
44 lines
1.3 KiB
Scheme
44 lines
1.3 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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;;; 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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(mes-use-module (mes let))
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(define (make-exception key . args)
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(cons* '*exception* key args))
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(define (exception? o)
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(and (pair? o) (eq? (car o) '*exception*)))
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(define (exception-key o)
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(if (exception? o) (cadr o)))
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(define (exception-args o)
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(if (exception? o) (cddr o)))
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(define (catch key thunk handler)
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(let ((result (thunk)))
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(if (and (exception? result)
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(or (eq? key (exception-key result))
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(eq? key #t)))
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(handler (exception-key result) (exception-args result))
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result)))
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(define throw make-exception)
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