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<p><strong>gensym</strong> <span><i>Function</i></span></p>
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<p><strong>Syntax:</strong></p>
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<p><span><b>gensym</b></span> &optional <em>x → new-symbol</em></p>
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<p><strong>Arguments and Values:</strong></p>
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<p><em>x</em>—a <span><i>string</i></span> or a non-negative <em>integer</em> . Complicated defaulting behavior; see below. <em>new-symbol</em>—a <span><i>fresh</i></span>, <em>uninterned symbol</em>.</p>
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<p><strong>Description:</strong></p>
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<p>Creates and returns a <span><i>fresh</i></span>, <em>uninterned symbol</em>, as if by calling <span><b>make-symbol</b></span>. (The only difference between <span><b>gensym</b></span> and <span><b>make-symbol</b></span> is in how the <em>new-symbol</em>’s <span><i>name</i></span> is determined.)</p>
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<p>The <span><i>name</i></span> of the <em>new-symbol</em> is the concatenation of a prefix, which defaults to "G", and a suffix, which is the decimal representation of a number that defaults to the <span><i>value</i></span> of <span><b>*gensym-counter*</b></span>.</p>
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<p>If <em>x</em> is supplied, and is a <span><i>string</i></span>, then that <span><i>string</i></span> is used as a prefix instead of "G" for this call to <span><b>gensym</b></span> only.</p>
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<p>If <em>x</em> is supplied, and is an <em>integer</em> , then that <em>integer</em> , instead of the <span><i>value</i></span> of <span><b>*gensym-counter*</b></span>, is used as the suffix for this call to <span><b>gensym</b></span> only.</p>
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<p>If and only if no explicit suffix is supplied, <span><b>*gensym-counter*</b></span> is incremented after it is used.</p>
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<p><strong>Examples:</strong></p>
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<div class="language-lisp codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-lisp codeBlock_bY9V thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">setq</span><span class="token plain"> sym1 </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">gensym</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #</span><span class="token lisp-property property" style="color:#36acaa">:G3142</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">symbol-package</span><span class="token plain"> sym1</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → NIL </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">setq</span><span class="token plain"> sym2 </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">gensym</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">100</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #</span><span class="token lisp-property property" style="color:#36acaa">:G100</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">setq</span><span class="token plain"> sym3 </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">gensym</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">100</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #</span><span class="token lisp-property property" style="color:#36acaa">:G100</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">eq</span><span class="token plain"> sym2 sym3</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → false </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">find-symbol</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"G100"</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → NIL, NIL </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">gensym</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"T"</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #</span><span class="token lisp-property property" style="color:#36acaa">:T3143</span><span class="token plain"> </span><br></span><span class="token-line"
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<p><strong>Side Effects:</strong></p>
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<p>Might increment <span><b>*gensym-counter*</b></span>.</p>
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<p><strong>Affected By:</strong></p>
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<span><b>*gensym-counter*</b></span>
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<p><strong>Exceptional Situations:</strong></p>
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<p>Should signal an error of <span><i>type</i></span> <span><b>type-error</b></span> if <em>x</em> is not a <span><i>string</i></span> or a non-negative <em>integer</em> .</p>
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<p><strong>See Also:</strong></p>
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<p><span><b>gentemp</b></span>, <span><b>*gensym-counter*</b></span></p>
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<p><strong>Notes:</strong></p>
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<p>The ability to pass a numeric argument to <span><b>gensym</b></span> has been deprecated; explicitly <span><i>binding</i></span> <span><b>*gensym-counter*</b></span> is now stylistically preferred. (The somewhat baroque conventions for the optional argument are historical in nature, and supported primarily for compatibility with older dialects of Lisp. In modern code, it is recommended that the only kind of argument used be a string prefix. In general, though, to obtain more flexible control of the <em>new-symbol</em>’s <span><i>name</i></span>, consider using <span><b>make-symbol</b></span> instead.)</p>
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<h2 class="anchor anchorWithStickyNavbar_LWe7" id="expanded-reference-gensym">Expanded Reference: gensym<a href="gensym_function.html#expanded-reference-gensym" class="hash-link" aria-label="Direct link to Expanded Reference: gensym" title="Direct link to Expanded Reference: gensym"></a></h2>
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<div class="theme-admonition theme-admonition-tip admonition_xJq3 alert alert--success"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_BuS1"><p>TODO: Please contribute to this page by adding explanations and examples</p></div></div>
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<div class="language-lisp codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-lisp codeBlock_bY9V thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">(</span><span class="token car">gensym</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/lisp-docs/cl-language-reference/tree/main/docs/chap-10/ba-c-dictionary/gensym_function.md" target="_blank" rel="noopener noreferrer" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"><span class="theme-last-updated">Last updated<!-- --> by <b>daninus14</b></span></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href="gensym-counter_variable.html"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">gensym-counter</div></a><a class="pagination-nav__link pagination-nav__link--next" href="gentemp_function.html"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">gentemp</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="gensym_function.html#expanded-reference-gensym" class="table-of-contents__link toc-highlight">Expanded Reference: gensym</a></li></ul></div></div></div></div></main></div></div></div><footer class="footer footer--dark"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title">Docs</div><ul class="footer__items clean-list"><li class="footer__item"><a href="../../../docs/tutorial.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Common Lisp Tutorial</a></li><li class="footer__item"><a href="../../index.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Common Lisp Technical Reference</a></li><li class="footer__item"><a href="../../../docs/help.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Help</a></li></ul></div><div class="col footer__col"><div class="footer__title">Community</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://stackoverflow.com/questions/tagged/common-lisp" target="_blank" rel="noopener noreferrer" class="footer__link-item">Stack Overflow<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://discord.gg/hhk46CE" target="_blank" rel="noopener norefer
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