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32ce4058db
* module/ice-9/control.scm (%): Add a single-argument case, which instates a default prompt with a default handler. * libguile/script.c (scm_compile_shell_switches): Wrap user programs in a default prompt. * module/system/repl/common.scm (repl-eval): REPL expressions are user programs too; wrap each one in a default prompt.
56 lines
2.2 KiB
Scheme
56 lines
2.2 KiB
Scheme
;;; Beyond call/cc
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;; Copyright (C) 2010 Free Software Foundation, Inc.
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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;;;; License as published by the Free Software Foundation; either
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;;;; version 3 of the License, or (at your option) any later version.
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;;;;
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;;;; This library 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 GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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;;; Code:
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(define-module (ice-9 control)
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#:re-export (call-with-prompt abort-to-prompt
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default-prompt-tag make-prompt-tag)
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#:export (% abort))
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(define (abort . args)
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(apply abort-to-prompt (default-prompt-tag) args))
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(define-syntax %
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(syntax-rules ()
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((_ expr)
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(call-with-prompt (default-prompt-tag)
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(lambda () expr)
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default-prompt-handler))
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((_ expr handler)
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(call-with-prompt (default-prompt-tag)
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(lambda () expr)
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handler))
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((_ tag expr handler)
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(call-with-prompt tag
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(lambda () expr)
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handler))))
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;; Each prompt tag has a type -- an expected set of arguments, and an unwritten
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;; contract of what its handler will do on an abort. In the case of the default
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;; prompt tag, we could choose to return values, exit nonlocally, or punt to the
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;; user.
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;;
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;; We choose the latter, by requiring that the user return one value, a
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;; procedure, to an abort to the prompt tag. That argument is then invoked with
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;; the continuation as an argument, within a reinstated default prompt. In this
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;; way the return value(s) from a default prompt are under the user's control.
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(define (default-prompt-handler k proc)
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(% (default-prompt-tag)
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(proc k)
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default-prompt-handler))
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