128 lines
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128 lines
8.1 KiB
HTML
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>Append/Reverse (Guile Reference Manual)</title>
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<meta name="description" content="Append/Reverse (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="Lists.html" rel="up" title="Lists">
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<link href="List-Modification.html" rel="next" title="List Modification">
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<link href="List-Selection.html" rel="prev" title="List Selection">
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<div class="subsubsection-level-extent" id="Append_002fReverse">
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<div class="nav-panel">
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<p>
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Next: <a href="List-Modification.html" accesskey="n" rel="next">List Modification</a>, Previous: <a href="List-Selection.html" accesskey="p" rel="prev">List Selection</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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</div>
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<hr>
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<h4 class="subsubsection" id="Append-and-Reverse"><span>6.6.9.5 Append and Reverse<a class="copiable-link" href="#Append-and-Reverse"> ¶</a></span></h4>
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<p><code class="code">append</code> and <code class="code">append!</code> are used to concatenate two or more
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lists in order to form a new list. <code class="code">reverse</code> and <code class="code">reverse!</code>
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return lists with the same elements as their arguments, but in reverse
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order. The procedure variants with an <code class="code">!</code> directly modify the
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pairs which form the list, whereas the other procedures create new
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pairs. This is why you should be careful when using the side-effecting
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variants.
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</p>
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<a class="index-entry-id" id="index-append-4"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-append"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">append</strong> <var class="def-var-arguments">lst … obj</var><a class="copiable-link" href="#index-append"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-append-1"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">append</strong><a class="copiable-link" href="#index-append-1"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-append_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">append!</strong> <var class="def-var-arguments">lst … obj</var><a class="copiable-link" href="#index-append_0021"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-append_0021-1"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">append!</strong><a class="copiable-link" href="#index-append_0021-1"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fappend"><span class="category-def">C Function: </span><span><strong class="def-name">scm_append</strong> <var class="def-var-arguments">(lstlst)</var><a class="copiable-link" href="#index-scm_005fappend"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fappend_005fx"><span class="category-def">C Function: </span><span><strong class="def-name">scm_append_x</strong> <var class="def-var-arguments">(lstlst)</var><a class="copiable-link" href="#index-scm_005fappend_005fx"> ¶</a></span></dt>
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<dd><p>Return a list comprising all the elements of lists <var class="var">lst</var> …
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<var class="var">obj</var>. If called with no arguments, return the empty list.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(append '(x) '(y)) ⇒ (x y)
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(append '(a) '(b c d)) ⇒ (a b c d)
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(append '(a (b)) '((c))) ⇒ (a (b) (c))
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</pre></div>
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<p>The last argument <var class="var">obj</var> may actually be any object; an improper
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list results if the last argument is not a proper list.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(append '(a b) '(c . d)) ⇒ (a b c . d)
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(append '() 'a) ⇒ a
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</pre></div>
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<p><code class="code">append</code> doesn’t modify the given lists, but the return may share
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structure with the final <var class="var">obj</var>. <code class="code">append!</code> is permitted, but
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not required, to modify the given lists to form its return.
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</p>
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<p>For <code class="code">scm_append</code> and <code class="code">scm_append_x</code>, <var class="var">lstlst</var> is a list
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of the list operands <var class="var">lst</var> … <var class="var">obj</var>. That <var class="var">lstlst</var>
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itself is not modified or used in the return.
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</p></dd></dl>
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<a class="index-entry-id" id="index-reverse-2"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-reverse"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">reverse</strong> <var class="def-var-arguments">lst</var><a class="copiable-link" href="#index-reverse"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-reverse_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">reverse!</strong> <var class="def-var-arguments">lst [newtail]</var><a class="copiable-link" href="#index-reverse_0021"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005freverse"><span class="category-def">C Function: </span><span><strong class="def-name">scm_reverse</strong> <var class="def-var-arguments">(lst)</var><a class="copiable-link" href="#index-scm_005freverse"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005freverse_005fx"><span class="category-def">C Function: </span><span><strong class="def-name">scm_reverse_x</strong> <var class="def-var-arguments">(lst, newtail)</var><a class="copiable-link" href="#index-scm_005freverse_005fx"> ¶</a></span></dt>
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<dd><p>Return a list comprising the elements of <var class="var">lst</var>, in reverse order.
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</p>
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<p><code class="code">reverse</code> constructs a new list. <code class="code">reverse!</code> is permitted, but
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not required, to modify <var class="var">lst</var> in constructing its return.
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</p>
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<p>For <code class="code">reverse!</code>, the optional <var class="var">newtail</var> is appended to the
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result. <var class="var">newtail</var> isn’t reversed, it simply becomes the list
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tail. For <code class="code">scm_reverse_x</code>, the <var class="var">newtail</var> parameter is
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mandatory, but can be <code class="code">SCM_EOL</code> if no further tail is required.
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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="List-Modification.html">List Modification</a>, Previous: <a href="List-Selection.html">List Selection</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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