122 lines
6.9 KiB
HTML
122 lines
6.9 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-1 Deleting (Guile Reference Manual)</title>
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<meta name="description" content="SRFI-1 Deleting (Guile Reference Manual)">
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<meta name="keywords" content="SRFI-1 Deleting (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_002d1.html" rel="up" title="SRFI-1">
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<link href="SRFI_002d1-Association-Lists.html" rel="next" title="SRFI-1 Association Lists">
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<link href="SRFI_002d1-Searching.html" rel="prev" title="SRFI-1 Searching">
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<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="SRFI_002d1-Deleting">
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<div class="nav-panel">
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<p>
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Next: <a href="SRFI_002d1-Association-Lists.html" accesskey="n" rel="next">Association Lists</a>, Previous: <a href="SRFI_002d1-Searching.html" accesskey="p" rel="prev">Searching</a>, Up: <a href="SRFI_002d1.html" accesskey="u" rel="up">SRFI-1 - List library</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="Deleting"><span>7.5.3.8 Deleting<a class="copiable-link" href="#Deleting"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-list-delete"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-delete-1"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">delete</strong> <var class="def-var-arguments">x lst [=]</var><a class="copiable-link" href="#index-delete-1"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-delete_0021-1"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">delete!</strong> <var class="def-var-arguments">x lst [=]</var><a class="copiable-link" href="#index-delete_0021-1"> ¶</a></span></dt>
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<dd><p>Return a list containing the elements of <var class="var">lst</var> but with those
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equal to <var class="var">x</var> deleted. The returned elements will be in the same
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order as they were in <var class="var">lst</var>.
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</p>
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<p>Equality is determined by the <var class="var">=</var> predicate, or <code class="code">equal?</code> if
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not given. An equality call is made just once for each element, but
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the order in which the calls are made on the elements is unspecified.
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</p>
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<p>The equality calls are always <code class="code">(= x elem)</code>, ie. the given <var class="var">x</var>
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is first. This means for instance elements greater than 5 can be
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deleted with <code class="code">(delete 5 lst <)</code>.
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</p>
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<p><code class="code">delete</code> does not modify <var class="var">lst</var>, but the return might share a
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common tail with <var class="var">lst</var>. <code class="code">delete!</code> may modify the structure
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of <var class="var">lst</var> to construct its return.
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</p>
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<p>These functions extend the core <code class="code">delete</code> and <code class="code">delete!</code>
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(see <a class="pxref" href="List-Modification.html">List Modification</a>) in accepting an equality predicate. See
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also <code class="code">lset-difference</code> (see <a class="pxref" href="SRFI_002d1-Set-Operations.html">Set Operations on Lists</a>) for
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deleting multiple elements from a list.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-delete_002dduplicates"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">delete-duplicates</strong> <var class="def-var-arguments">lst [=]</var><a class="copiable-link" href="#index-delete_002dduplicates"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-delete_002dduplicates_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">delete-duplicates!</strong> <var class="def-var-arguments">lst [=]</var><a class="copiable-link" href="#index-delete_002dduplicates_0021"> ¶</a></span></dt>
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<dd><p>Return a list containing the elements of <var class="var">lst</var> but without
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duplicates.
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</p>
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<p>When elements are equal, only the first in <var class="var">lst</var> is retained.
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Equal elements can be anywhere in <var class="var">lst</var>, they don’t have to be
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adjacent. The returned list will have the retained elements in the
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same order as they were in <var class="var">lst</var>.
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</p>
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<p>Equality is determined by the <var class="var">=</var> predicate, or <code class="code">equal?</code> if
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not given. Calls <code class="code">(= x y)</code> are made with element <var class="var">x</var> being
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before <var class="var">y</var> in <var class="var">lst</var>. A call is made at most once for each
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combination, but the sequence of the calls across the elements is
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unspecified.
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</p>
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<p><code class="code">delete-duplicates</code> does not modify <var class="var">lst</var>, but the return
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might share a common tail with <var class="var">lst</var>. <code class="code">delete-duplicates!</code>
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may modify the structure of <var class="var">lst</var> to construct its return.
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</p>
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<p>In the worst case, this is an <em class="math">O(N^2)</em> algorithm because it must
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check each element against all those preceding it. For long lists it
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is more efficient to sort and then compare only adjacent elements.
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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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Next: <a href="SRFI_002d1-Association-Lists.html">Association Lists</a>, Previous: <a href="SRFI_002d1-Searching.html">Searching</a>, Up: <a href="SRFI_002d1.html">SRFI-1 - List library</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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