78 lines
3.6 KiB
HTML
78 lines
3.6 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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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-41 Stream Fundamentals (Guile Reference Manual)</title>
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<meta name="description" content="SRFI-41 Stream Fundamentals (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_002d41.html" rel="up" title="SRFI-41">
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<link href="SRFI_002d41-Stream-Primitives.html" rel="next" title="SRFI-41 Stream Primitives">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="SRFI_002d41-Stream-Fundamentals">
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<div class="nav-panel">
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<p>
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Next: <a href="SRFI_002d41-Stream-Primitives.html" accesskey="n" rel="next">SRFI-41 Stream Primitives</a>, Up: <a href="SRFI_002d41.html" accesskey="u" rel="up">SRFI-41 - Streams</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="SRFI_002d41-Stream-Fundamentals-1"><span>7.5.28.1 SRFI-41 Stream Fundamentals<a class="copiable-link" href="#SRFI_002d41-Stream-Fundamentals-1"> ¶</a></span></h4>
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<p>SRFI-41 Streams are based on two mutually-recursive abstract data types:
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An object of the <code class="code">stream</code> abstract data type is a promise that,
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when forced, is either <code class="code">stream-null</code> or is an object of type
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<code class="code">stream-pair</code>. An object of the <code class="code">stream-pair</code> abstract data
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type contains a <code class="code">stream-car</code> and a <code class="code">stream-cdr</code>, which must be
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a <code class="code">stream</code>. The essential feature of streams is the systematic
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suspensions of the recursive promises between the two data types.
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</p>
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<p>The object stored in the <code class="code">stream-car</code> of a <code class="code">stream-pair</code> is a
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promise that is forced the first time the <code class="code">stream-car</code> is accessed;
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its value is cached in case it is needed again. The object may have any
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type, and different stream elements may have different types. If the
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<code class="code">stream-car</code> is never accessed, the object stored there is never
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evaluated. Likewise, the <code class="code">stream-cdr</code> is a promise to return a
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stream, and is only forced on demand.
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</p>
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</div>
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</body>
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</html>
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