112 lines
7.2 KiB
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112 lines
7.2 KiB
HTML
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>List Selection (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="Lists.html" rel="up" title="Lists">
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<div class="subsubsection-level-extent" id="List-Selection">
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<p>
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Next: <a href="Append_002fReverse.html" accesskey="n" rel="next">Append and Reverse</a>, Previous: <a href="List-Constructors.html" accesskey="p" rel="prev">List Constructors</a>, Up: <a href="Lists.html" accesskey="u" rel="up">Lists</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="subsubsection" id="List-Selection-1"><span>6.6.9.4 List Selection<a class="copiable-link" href="#List-Selection-1"> ¶</a></span></h4>
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<p>These procedures are used to get some information about a list, or to
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retrieve one or more elements of a list.
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</p>
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<a class="index-entry-id" id="index-length-2"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-length"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">length</strong> <var class="def-var-arguments">lst</var><a class="copiable-link" href="#index-length"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005flength"><span class="category-def">C Function: </span><span><strong class="def-name">scm_length</strong> <var class="def-var-arguments">(lst)</var><a class="copiable-link" href="#index-scm_005flength"> ¶</a></span></dt>
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<dd><p>Return the number of elements in list <var class="var">lst</var>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-last_002dpair"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">last-pair</strong> <var class="def-var-arguments">lst</var><a class="copiable-link" href="#index-last_002dpair"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005flast_005fpair"><span class="category-def">C Function: </span><span><strong class="def-name">scm_last_pair</strong> <var class="def-var-arguments">(lst)</var><a class="copiable-link" href="#index-scm_005flast_005fpair"> ¶</a></span></dt>
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<dd><p>Return the last pair in <var class="var">lst</var>, signaling an error if
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<var class="var">lst</var> is circular.
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</p></dd></dl>
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<a class="index-entry-id" id="index-list_002dref-2"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-list_002dref"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">list-ref</strong> <var class="def-var-arguments">list k</var><a class="copiable-link" href="#index-list_002dref"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005flist_005fref"><span class="category-def">C Function: </span><span><strong class="def-name">scm_list_ref</strong> <var class="def-var-arguments">(list, k)</var><a class="copiable-link" href="#index-scm_005flist_005fref"> ¶</a></span></dt>
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<dd><p>Return the <var class="var">k</var>th element from <var class="var">list</var>.
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</p></dd></dl>
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<a class="index-entry-id" id="index-list_002dtail-2"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-list_002dtail"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">list-tail</strong> <var class="def-var-arguments">lst k</var><a class="copiable-link" href="#index-list_002dtail"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-list_002dcdr_002dref"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">list-cdr-ref</strong> <var class="def-var-arguments">lst k</var><a class="copiable-link" href="#index-list_002dcdr_002dref"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005flist_005ftail"><span class="category-def">C Function: </span><span><strong class="def-name">scm_list_tail</strong> <var class="def-var-arguments">(lst, k)</var><a class="copiable-link" href="#index-scm_005flist_005ftail"> ¶</a></span></dt>
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<dd><p>Return the "tail" of <var class="var">lst</var> beginning with its <var class="var">k</var>th element.
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The first element of the list is considered to be element 0.
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</p>
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<p><code class="code">list-tail</code> and <code class="code">list-cdr-ref</code> are identical. It may help to
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think of <code class="code">list-cdr-ref</code> as accessing the <var class="var">k</var>th cdr of the list,
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or returning the results of cdring <var class="var">k</var> times down <var class="var">lst</var>.
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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_002dhead"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">list-head</strong> <var class="def-var-arguments">lst k</var><a class="copiable-link" href="#index-list_002dhead"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005flist_005fhead"><span class="category-def">C Function: </span><span><strong class="def-name">scm_list_head</strong> <var class="def-var-arguments">(lst, k)</var><a class="copiable-link" href="#index-scm_005flist_005fhead"> ¶</a></span></dt>
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<dd><p>Copy the first <var class="var">k</var> elements from <var class="var">lst</var> into a new list, and
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return it.
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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="Append_002fReverse.html">Append and Reverse</a>, Previous: <a href="List-Constructors.html">List Constructors</a>, Up: <a href="Lists.html">Lists</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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