90 lines
4.7 KiB
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90 lines
4.7 KiB
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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<title>Continuation Barriers (Guile Reference Manual)</title>
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Control-Mechanisms.html" rel="up" title="Control Mechanisms">
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<body lang="en">
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<div class="subsection-level-extent" id="Continuation-Barriers">
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<div class="nav-panel">
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<p>
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Previous: <a href="Handling-Errors.html" accesskey="p" rel="prev">How to Handle Errors</a>, Up: <a href="Control-Mechanisms.html" accesskey="u" rel="up">Controlling the Flow of Program Execution</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
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<h4 class="subsection" id="Continuation-Barriers-1"><span>6.11.14 Continuation Barriers<a class="copiable-link" href="#Continuation-Barriers-1"> ¶</a></span></h4>
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<p>The non-local flow of control caused by continuations might sometimes
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not be wanted. You can use <code class="code">with-continuation-barrier</code> to erect
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fences that continuations can not pass.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-with_002dcontinuation_002dbarrier"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">with-continuation-barrier</strong> <var class="def-var-arguments">proc</var><a class="copiable-link" href="#index-with_002dcontinuation_002dbarrier"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fwith_005fcontinuation_005fbarrier"><span class="category-def">C Function: </span><span><strong class="def-name">scm_with_continuation_barrier</strong> <var class="def-var-arguments">(proc)</var><a class="copiable-link" href="#index-scm_005fwith_005fcontinuation_005fbarrier"> ¶</a></span></dt>
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<dd><p>Call <var class="var">proc</var> and return its result. Do not allow the invocation of
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continuations that would leave or enter the dynamic extent of the call
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to <code class="code">with-continuation-barrier</code>. Such an attempt causes an error
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to be signaled.
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</p>
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<p>Throws (such as errors) that are not caught from within <var class="var">proc</var> are
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caught by <code class="code">with-continuation-barrier</code>. In that case, a short
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message is printed to the current error port and <code class="code">#f</code> is returned.
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</p>
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<p>Thus, <code class="code">with-continuation-barrier</code> returns exactly once.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fc_005fwith_005fcontinuation_005fbarrier"><span class="category-def">C Function: </span><span><code class="def-type">void *</code> <strong class="def-name">scm_c_with_continuation_barrier</strong> <code class="def-code-arguments">(void *(*func) (void *), void *data)</code><a class="copiable-link" href="#index-scm_005fc_005fwith_005fcontinuation_005fbarrier"> ¶</a></span></dt>
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<dd><p>Like <code class="code">scm_with_continuation_barrier</code> but call <var class="var">func</var> on
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<var class="var">data</var>. When an error is caught, <code class="code">NULL</code> is returned.
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</p></dd></dl>
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