138 lines
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138 lines
7.7 KiB
HTML
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<title>Generic Function Internals (Guile Reference Manual)</title>
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<link href="The-Metaobject-Protocol.html" rel="up" title="The Metaobject Protocol">
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<link href="Generic-Function-Invocation.html" rel="next" title="Generic Function Invocation">
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<div class="subsection-level-extent" id="Generic-Function-Internals">
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<p>
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Next: <a href="Generic-Function-Invocation.html" accesskey="n" rel="next">Generic Function Invocation</a>, Previous: <a href="Method-Definition-Internals.html" accesskey="p" rel="prev">Method Definition Internals</a>, Up: <a href="The-Metaobject-Protocol.html" accesskey="u" rel="up">The Metaobject Protocol</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="subsection" id="Generic-Function-Internals-1"><span>8.11.9 Generic Function Internals<a class="copiable-link" href="#Generic-Function-Internals-1"> ¶</a></span></h4>
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<p><code class="code">define-generic</code> calls <code class="code">ensure-generic</code> to upgrade a
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pre-existing procedure value, or <code class="code">make</code> with metaclass
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<code class="code"><generic></code> to create a new generic function.
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</p>
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<p><code class="code">define-accessor</code> calls <code class="code">ensure-accessor</code> to upgrade a
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pre-existing procedure value, or <code class="code">make-accessor</code> to create a new
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accessor.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-ensure_002dgeneric"><span class="category-def">procedure: </span><span><strong class="def-name">ensure-generic</strong> <var class="def-var-arguments">old-definition [name]</var><a class="copiable-link" href="#index-ensure_002dgeneric"> ¶</a></span></dt>
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<dd><p>Return a generic function with name <var class="var">name</var>, if possible by using or
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upgrading <var class="var">old-definition</var>. If unspecified, <var class="var">name</var> defaults to
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<code class="code">#f</code>.
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</p>
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<p>If <var class="var">old-definition</var> is already a generic function, it is returned
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unchanged.
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</p>
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<p>If <var class="var">old-definition</var> is a Scheme procedure or procedure-with-setter,
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<code class="code">ensure-generic</code> returns a new generic function that uses
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<var class="var">old-definition</var> for its default procedure and setter.
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</p>
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<p>Otherwise <code class="code">ensure-generic</code> returns a new generic function with no
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defaults and no methods.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-make_002dgeneric"><span class="category-def">procedure: </span><span><strong class="def-name">make-generic</strong> <var class="def-var-arguments">[name]</var><a class="copiable-link" href="#index-make_002dgeneric"> ¶</a></span></dt>
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<dd><p>Return a new generic function with name <code class="code">(car <var class="var">name</var>)</code>. If
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unspecified, <var class="var">name</var> defaults to <code class="code">#f</code>.
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</p></dd></dl>
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<p><code class="code">ensure-generic</code> calls <code class="code">make</code> with metaclasses
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<code class="code"><generic></code> and <code class="code"><generic-with-setter></code>, depending on the
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previous value of the variable that it is trying to upgrade.
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</p>
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<p><code class="code">make-generic</code> is a simple wrapper for <code class="code">make</code> with metaclass
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<code class="code"><generic></code>.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-ensure_002daccessor"><span class="category-def">procedure: </span><span><strong class="def-name">ensure-accessor</strong> <var class="def-var-arguments">proc [name]</var><a class="copiable-link" href="#index-ensure_002daccessor"> ¶</a></span></dt>
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<dd><p>Return an accessor with name <var class="var">name</var>, if possible by using or
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upgrading <var class="var">proc</var>. If unspecified, <var class="var">name</var> defaults to <code class="code">#f</code>.
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</p>
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<p>If <var class="var">proc</var> is already an accessor, it is returned unchanged.
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</p>
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<p>If <var class="var">proc</var> is a Scheme procedure, procedure-with-setter or generic
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function, <code class="code">ensure-accessor</code> returns an accessor that reuses the
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reusable elements of <var class="var">proc</var>.
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</p>
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<p>Otherwise <code class="code">ensure-accessor</code> returns a new accessor with no defaults
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and no methods.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-make_002daccessor"><span class="category-def">procedure: </span><span><strong class="def-name">make-accessor</strong> <var class="def-var-arguments">[name]</var><a class="copiable-link" href="#index-make_002daccessor"> ¶</a></span></dt>
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<dd><p>Return a new accessor with name <code class="code">(car <var class="var">name</var>)</code>. If
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unspecified, <var class="var">name</var> defaults to <code class="code">#f</code>.
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</p></dd></dl>
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<p><code class="code">ensure-accessor</code> calls <code class="code">make</code> with
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metaclass <code class="code"><generic-with-setter></code>, as well as calls to
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<code class="code">ensure-generic</code>, <code class="code">make-accessor</code> and (tail recursively)
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<code class="code">ensure-accessor</code>.
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</p>
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<p><code class="code">make-accessor</code> calls <code class="code">make</code> twice, first
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with metaclass <code class="code"><generic></code> to create a generic function for the
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setter, then with metaclass <code class="code"><generic-with-setter></code> to create the
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accessor, passing the setter generic function as the value of the
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<code class="code">#:setter</code> keyword.
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</p>
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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="Generic-Function-Invocation.html">Generic Function Invocation</a>, Previous: <a href="Method-Definition-Internals.html">Method Definition Internals</a>, Up: <a href="The-Metaobject-Protocol.html">The Metaobject Protocol</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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