140 lines
7.9 KiB
HTML
140 lines
7.9 KiB
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<!DOCTYPE html>
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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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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>SRFI-171 Helpers (Guile Reference Manual)</title>
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<meta name="description" content="SRFI-171 Helpers (Guile Reference Manual)">
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<link href="index.html" rel="start" title="Top">
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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="SRFI_002d171.html" rel="up" title="SRFI-171">
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<link href="SRFI_002d171-Transducers.html" rel="prev" title="SRFI-171 Transducers">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="SRFI_002d171-Helpers">
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<div class="nav-panel">
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<p>
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Previous: <a href="SRFI_002d171-Transducers.html" accesskey="p" rel="prev">Transducers</a>, Up: <a href="SRFI_002d171.html" accesskey="u" rel="up">Transducers</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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</div>
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<hr>
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<h4 class="subsubsection" id="Helper-functions-for-writing-transducers"><span>7.5.47.5 Helper functions for writing transducers<a class="copiable-link" href="#Helper-functions-for-writing-transducers"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-transducers-helpers"></a>
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<p>These functions are in the <code class="code">(srfi srfi-171 meta)</code> module and are only
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usable when you want to write your own transducers.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-reduced"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">reduced</strong> <var class="def-var-arguments">value</var><a class="copiable-link" href="#index-reduced"> ¶</a></span></dt>
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<dd><p>Wraps a value in a <code class="code"><reduced></code> container, signaling that the
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reduction should stop.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-reduced_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">reduced?</strong> <var class="def-var-arguments">value</var><a class="copiable-link" href="#index-reduced_003f"> ¶</a></span></dt>
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<dd><p>Returns #t if value is a <code class="code"><reduced></code> record.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-unreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">unreduce</strong> <var class="def-var-arguments">reduced-container</var><a class="copiable-link" href="#index-unreduce"> ¶</a></span></dt>
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<dd><p>Returns the value in reduced-container.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-ensure_002dreduced"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">ensure-reduced</strong> <var class="def-var-arguments">value</var><a class="copiable-link" href="#index-ensure_002dreduced"> ¶</a></span></dt>
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<dd><p>Wraps value in a <code class="code"><reduced></code> container if it is not already reduced.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-preserving_002dreduced"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">preserving-reduced</strong> <var class="def-var-arguments">reducer</var><a class="copiable-link" href="#index-preserving_002dreduced"> ¶</a></span></dt>
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<dd><p>Wraps <code class="code">reducer</code> in another reducer that encapsulates any returned
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reduced value in another reduced container. This is useful in places
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where you re-use a reducer with [collection]-reduce. If the reducer
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returns a reduced value, [collection]-reduce unwraps it. Unless handled,
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this leads to the reduction continuing.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-list_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">list-reduce</strong> <var class="def-var-arguments">f identity lst</var><a class="copiable-link" href="#index-list_002dreduce"> ¶</a></span></dt>
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<dd><p>The reducing function used internally by <code class="code">list-transduce</code>. <var class="var">f</var>
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is a reducer as returned by a transducer. <var class="var">identity</var> is the
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identity (sometimes called "seed") of the reduction. <var class="var">lst</var> is a
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list. If <var class="var">f</var> returns a reduced value, the reduction stops
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immediately and the unreduced value is returned.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-vector_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-reduce</strong> <var class="def-var-arguments">f identity vec</var><a class="copiable-link" href="#index-vector_002dreduce"> ¶</a></span></dt>
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<dd><p>The vector version of list-reduce.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-string_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">string-reduce</strong> <var class="def-var-arguments">f identity str</var><a class="copiable-link" href="#index-string_002dreduce"> ¶</a></span></dt>
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<dd><p>The string version of list-reduce.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-bytevector_002du8_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">bytevector-u8-reduce</strong> <var class="def-var-arguments">f identity bv</var><a class="copiable-link" href="#index-bytevector_002du8_002dreduce"> ¶</a></span></dt>
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<dd><p>The bytevector-u8 version of list-reduce.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-port_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">port-reduce</strong> <var class="def-var-arguments">f identity reader port</var><a class="copiable-link" href="#index-port_002dreduce"> ¶</a></span></dt>
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<dd><p>The port version of list-reduce. It reduces over port using reader
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until reader returns the EOF object.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-generator_002dreduce"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">generator-reduce</strong> <var class="def-var-arguments">f identity gen</var><a class="copiable-link" href="#index-generator_002dreduce"> ¶</a></span></dt>
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<dd><p>The generator version of list-reduce. It reduces over <code class="code">gen</code> until
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it returns the EOF object
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</p></dd></dl>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Previous: <a href="SRFI_002d171-Transducers.html">Transducers</a>, Up: <a href="SRFI_002d171.html">Transducers</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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</div>
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</body>
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</html>
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