55 lines
5.9 KiB
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55 lines
5.9 KiB
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<title>CLiki: ORF</title>
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<span class="hidden">CLiki - ORF</span>
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<div id="content"><div id="content-area"><div id="article-title">ORF</div><div id="article">A macro seen in some utility/<a href="convenience library.html" class="internal">convenience</a> layers. A simple definition (from <a href="McCLIM.html" class="internal">McCLIM</a>) is:<p><div class="code"><span class="nonparen"><span class="paren1">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/mac_define-modify-macro.html" class="symbol"><i><span class="symbol">define-modify-macro</span></i></a> orf <span class="paren2">(<span class="nonparen">&rest args</span>)</span> <a href="https://www.cliki.net/site/HyperSpec/Body/any_or.html" class="symbol">or</a></span>)</span></span></div><p>Another possibility is to modify the place only <em>if</em> it's null. This definition is more involved:<p><div class="code"><span class="nonparen"><span class="paren1">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/mac_defmacro.html" class="symbol"><i><span class="symbol">defmacro</span></i></a> orf <span class="paren2">(<span class="nonparen">place &rest forms &environment environment</span>)</span>
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<span class="paren2">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/mac_multiple-value-bind.html" class="symbol">multiple-value-bind</a> <span class="paren3">(<span class="nonparen">temps vals news writer reader</span>)</span> <span class="paren3">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/fun_get-setf-expansion.html" class="symbol">get-setf-expansion</a> place environment</span>)</span>
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<span class="paren3">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/speope_letcm_letst.html" class="symbol"><i><span class="symbol">let*</span></i></a> <span class="paren4">(<span class="nonparen"><span class="paren5">(<span class="nonparen">new-form `<span class="paren6">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/any_or.html" class="symbol">or</a> ,@forms</span>)</span></span>)</span> <span class="paren5">(<span class="nonparen">set-form `<span class="paren6">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/mac_multiple-value-bind.html" class="symbol">multiple-value-bind</a> ,news ,new-form ,writer</span>)</span></span>)</span></span>)</span>
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`<span class="paren4">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/speope_letcm_letst.html" class="symbol"><i><span class="symbol">let*</span></i></a> <span class="paren5">(<span class="nonparen">,.<span class="paren6">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/fun_mapccm_ma_istcm_mapcon.html" class="symbol">mapcar</a> #'<a href="https://www.cliki.net/site/HyperSpec/Body/any_list.html" class="symbol">list</a> temps vals</span>)</span></span>)</span> <span class="paren5">(<span class="nonparen"><a href="https://www.cliki.net/site/HyperSpec/Body/any_or.html" class="symbol">or</a> ,reader ,set-form</span>)</span></span>)</span></span>)</span></span>)</span></span>)</span></span></div><p>There's also an <a href="https://github.com/qitab/ace.core/blob/master/atomic.lisp">atomic version of <tt>orf</tt></a>, using <a href="SBCL.html" class="internal">SBCL</a>'s <a href="https://koji-kojiro.github.io/sb-docs/build/html/sb-ext/function/GET-CAS-EXPANSION.html"><tt>get-cas-expansion</tt></a>.<p><hr>
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<a href="macro example.html" class="category">macro example</a></div></div>
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<div id="footer" class="buttonbar"><ul><li><a href="ORF.html">Current version</a></li>
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<li><a href="https://www.cliki.net/site/history?article=ORF">History</a></li>
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