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<!-- -->
<!-- -->
<p><strong>assert</strong> <span><i>Macro</i></span></p>
<p><strong>Syntax:</strong></p>
<p><span><b>assert</b></span> <em>test-form</em> [(<span><i>{place}</i></span>*) [<em>datum-form {argument-form}</em>*]]</p>
<p>→ <span><b>nil</b></span></p>
<p><strong>Arguments and Values:</strong></p>
<p><em>test-form</em>—a <span><i>form</i></span>; always evaluated.</p>
<p><span><i>place</i></span>—a <span><i>place</i></span>; evaluated if an error is signaled.</p>
<p><em>datum-form</em>—a <span><i>form</i></span> that evaluates to a <em>datum</em>. Evaluated each time an error is to be signaled, or not at all if no error is to be signaled.</p>
<p><em>argument-form</em>—a <span><i>form</i></span> that evaluates to an <span><i>argument</i></span>. Evaluated each time an error is to be signaled, or not at all if no error is to be signaled.</p>
<p><em>datum</em>, <span><i>arguments</i></span>—<span><i>designators</i></span> for a <span><i>condition</i></span> of default type <span><b>error</b></span>. (These <span><i>designators</i></span> are the result of evaluating <em>datum-form</em> and each of the <em>argument-forms</em>.)</p>
<span><b>assert</b></span>
<p><strong>Description:</strong></p>
<p><span><b>assert</b></span> assures that <em>test-form</em> evaluates to <span><i>true</i></span>. If <em>test-form</em> evaluates to <span><i>false</i></span>, <span><b>assert</b></span> signals a <em>correctable error</em> (denoted by <em>datum</em> and <span><i>arguments</i></span>). Continuing from this error using the <strong>continue</strong> <span><i>restart</i></span> makes it possible for the user to alter the values of the <span><i>places</i></span> before <span><b>assert</b></span> evaluates <em>test-form</em> again. If the value of <em>test-form</em> is <span><i>non-nil</i></span>, <span><b>assert</b></span> returns <span><b>nil</b></span>.</p>
<p>The <span><i>places</i></span> are <span><i>generalized references</i></span> to data upon which <em>test-form</em> depends, whose values can be changed by the user in attempting to correct the error. <span><i>Subforms</i></span> of each <span><i>place</i></span> are only evaluated if an error is signaled, and might be re-evaluated if the error is re-signaled (after continuing without actually fixing the problem). The order of evaluation of the <span><i>places</i></span> is not specified; see Section 5.1.1.1 (Evaluation of Subforms to Places). If a <em>place form</em> is supplied that produces more values than there are store variables, the extra values are ignored. If the supplied <span><i>form</i></span> produces fewer values than there are store variables, the missing values are set to <span><b>nil</b></span>.</p>
<p><strong>Examples:</strong></p>
<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"> x </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">make-array</span><span class="token plain"> ’</span><span class="token punctuation" style="color:#393A34">(</span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">5</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:initial-element</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">→ #2A</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">3</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</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"> y </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">make-array</span><span class="token plain"> ’</span><span class="token punctuation" style="color:#393A34">(</span><span class="token number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">5</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:initial-element</span><span class="token plain"> </span><
<p><strong>Affected By:</strong></p>
<span><b>*break-on-signals*</b></span>
<p>The set of active <span><i>condition handlers</i></span>.</p>
<p><strong>See Also:</strong></p>
<p><span><b>check-type</b></span>, <span><b>error</b></span>, Section 5.1 (Generalized Reference)</p>
<p><strong>Notes:</strong></p>
<p>The debugger need not include the <em>test-form</em> in the error message, and the <span><i>places</i></span> should not be included in the message, but they should be made available for the user’s perusal. If the user gives the “continue” command, the values of any of the references can be altered. The details of this depend on the implementation’s style of user interface.</p>
<h2 class="anchor anchorWithStickyNavbar_LWe7" id="expanded-reference-assert">Expanded Reference: assert<a href="assert_macro.html#expanded-reference-assert" class="hash-link" aria-label="Direct link to Expanded Reference: assert" title="Direct link to Expanded Reference: assert">​</a></h2>
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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">assert</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-9/j-c-dictionary/assert_macro.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="../../category/92-conditions-dictionary.html"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">9.2 Conditions Dictionary</div></a><a class="pagination-nav__link pagination-nav__link--next" href="break-on-signals_variable.html"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">break-on-signals</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="assert_macro.html#expanded-reference-assert" class="table-of-contents__link toc-highlight">Expanded Reference: assert</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"
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