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Introduction</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-2/c-b-character-syntax.html">2. Syntax</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="../d-b-evaluation.html">3. 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href="../d-f-error-checking-in-function-calls.html">3.5 Error Checking in Function Calls</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="../d-g-traversal-rules-and-side-effects.html">3.6 Traversal Rules and Side Effects</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="../d-h-destructive-operations.html">3.7 Destructive Operations</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-2 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--active" aria-expanded="true" tabindex="0" href="../../category/38-evaluation-and-compilation-dictionary.html">3.8 Evaluation and Compilation Dictionary</a><button aria-label="Collapse sidebar category '3.8 Evaluation and Compilation Dictionary'" type="button" class="clean-btn 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href="declaration_declaration.html">declaration</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="declare_symbol.html">declare</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="define-compiler-macro_macro.html">define-compiler-macro</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="define-symbol-macro_macro.html">define-symbol-macro</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="defmacro_macro.html">defmacro</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="dynamic-extent_declaration.html">dynamic-extent</a></li><li 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macroexpand-1</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="optimize_declaration.html">optimize</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="proclaim_function.html">proclaim</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="quote_special-operator.html">quote</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="special-operator-p_function.html">special-operator-p</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="special_declaration.html">special</a></li><li class="theme-doc-sidebar-item-link 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Types and Classes</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-5/f-b-generalized-reference.html">5. Data and Control Flow</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-6/g-b-the-loop-facility.html">6. Iteration</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-7/h-b-object-creation-and-initialization.html">7. Objects</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../category/81-structures-dictionary.html">8. Structures</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-9/j-b-condition-system-concepts.html">9. Conditions</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-10/ba-b-symbol-concepts.html">10. Symbols</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-11/bb-b-package-concepts.html">11. Packages</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-12/bc-b-number-concepts.html">12. Numbers</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-13/bd-b-character-concepts.html">13. Characters</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-14/be-b-cons-concepts.html">14. Conses</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-15/bf-b-array-concepts.html">15. Arrays</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-16/bg-b-string-concepts.html">16. Strings</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-17/bh-b-sequence-concepts.html">17. Sequences</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-18/bi-b-hash-table-concepts.html">18. Hash Tables</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-19/bj-b-overview-of-filenames.html">19. Filenames</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-20/ca-b-file-system-concepts.html">20. Files</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-21/cb-b-stream-concepts.html">21. Streams</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-22/cc-b-the-lisp-printer.html">22. Printer</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-23/cd-b-reader-concepts.html">23. Reader</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-24/ce-b-system-construction-concepts.html">24. System Construction</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-25/cf-b-the-external-environment.html">25. External Environment</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../environments.html">26. Environments</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../meta-object-protocol.html">27. Meta Object Protocol</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../data-structures.html">28. Data Structures</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../portability/trivial-packages.html">29. Portability</a></div></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="../../dictionary-entries.html">dictionary-entries</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-26/intro.html">Glossary</a></div></li></ul></nav></div></div></aside><main class="docMainContainer_TBSr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="../../index.html"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">3. Evaluation and Compilation</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><a class="breadcrumbs__link" itemprop="item" href="../../category/38-evaluation-and-compilation-dictionary.html"><span itemprop="name">3.8 Evaluation and Compilation Dictionary</span></a><meta itemprop="position" content="2"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">special</span><meta itemprop="position" content="3"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><h1>special</h1>
|
||
<!-- -->
|
||
<!-- -->
|
||
<p><strong>special</strong> <span><i>Declaration</i></span></p>
|
||
<p><strong>Syntax:</strong></p>
|
||
<p>(special <em>{var}</em>*)</p>
|
||
<p><strong>Arguments:</strong></p>
|
||
<p><em>var</em>—a <span><i>symbol</i></span>.</p>
|
||
<p><strong>Valid Context:</strong></p>
|
||
<p><span><i>declaration</i></span> or <span><i>proclamation</i></span></p>
|
||
<p><strong>Binding Types Aected:</strong></p>
|
||
<span><i>variable</i></span>
|
||
<p><strong>Description:</strong></p>
|
||
<p>Specifies that all of the <em>vars</em> named are dynamic. This specifier a↵ects variable <span><i>bindings</i></span> and a↵ects references. All variable <span><i>bindings</i></span> a↵ected are made to be dynamic <span><i>bindings</i></span>, and a↵ected variable references refer to the current dynamic <span><i>binding</i></span>. For example:</p>
|
||
<p>(defun hack (thing *mod*) ;The binding of the parameter</p>
|
||
<p>(declare (special *mod*)) ; *mod* is visible to hack1,</p>
|
||
<p>(hack1 (car thing))) ; but not that of thing.</p>
|
||
<p>(defun hack1 (arg)</p>
|
||
<p>(declare (special *mod*)) ;Declare references to *mod*</p>
|
||
<p>;within hack1 to be special.</p>
|
||
<p>(if (atom arg) *mod*</p>
|
||
<p>(cons (hack1 (car arg)) (hack1 (cdr arg)))))</p>
|
||
<p>A <span><b>special</b></span> declaration does not a↵ect inner <span><i>bindings</i></span> of a <em>var</em>; the inner <span><i>bindings</i></span> implicitly shadow a <span><b>special</b></span> declaration and must be explicitly re-declared to be <span><b>special</b></span>. <span><b>special</b></span> declarations never apply to function <span><i>bindings</i></span>.</p>
|
||
<p><span><b>special</b></span> declarations can be either <span><i>bound declarations</i></span>, a↵ecting both a binding and references, or <span><i>free declarations</i></span>, a↵ecting only references, depending on whether the declaration is attached to a variable binding.</p>
|
||
<p>When used in a <span><i>proclamation</i></span>, a <span><b>special</b></span> <span><i>declaration specifier</i></span> applies to all <span><i>bindings</i></span> as well as to all references of the mentioned variables. For example, after</p>
|
||
<p>(declaim (special x))</p>
|
||
<p>Evaluation and</p>
|
||
<span><b>special</b></span>
|
||
<p>then in a function definition such as</p>
|
||
<p>(defun example (x) ...)</p>
|
||
<p>the parameter x is bound as a dynamic variable rather than as a lexical variable.</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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">declare-eg</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments argument variable" style="color:#36acaa">y</span><span class="token defun punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">;this y is special </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 declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> y</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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">y</span><span class="token plain"> </span><span class="token boolean" style="color:#36acaa">t</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 comment" style="color:#999988;font-style:italic">;this y is lexical </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">list</span><span class="token plain"> y </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">locally</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> y</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> y</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</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 comment" style="color:#999988;font-style:italic">;this y refers to the </span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">;special binding of y </span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">*!* DECLARE-EG </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">declare-eg</span><span class="token plain"> </span><span class="token boolean" style="color:#36acaa">nil</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 car">T</span><span class="token plain"> NIL</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 car">setf</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">symbol-value</span><span class="token plain"> ’x</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">6</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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">foo</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments argument variable" style="color:#36acaa">x</span><span class="token defun punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">;a lexical binding of x </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">print</span><span class="token plain"> x</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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">x</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">1+ x</span><span class="token punctuation" style="color:#393A34">)</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 comment" style="color:#999988;font-style:italic">;a special binding of x </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 declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> x</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 comment" style="color:#999988;font-style:italic">;and a lexical reference </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">bar</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 plain">1+ x</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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">bar</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments"></span><span class="token defun 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 car">print</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">locally</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> x</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"> x</span><span class="token punctuation" style="color:#393A34">)</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 car">foo</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">10</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 number" style="color:#36acaa">10</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">▷ </span><span class="token number" style="color:#36acaa">11</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">*!* </span><span class="token number" style="color:#36acaa">11</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">setf</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">symbol-value</span><span class="token plain"> ’x</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">6</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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">bar</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments argument variable" style="color:#36acaa">x</span><span class="token defun arguments"> </span><span class="token defun arguments argument variable" style="color:#36acaa">y</span><span class="token defun punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">;[1] 1st occurrence of x </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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">old-x</span><span class="token plain"> x</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">;[2] 2nd occurrence of x – same as 1st occurrence </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">x</span><span class="token plain"> y</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 comment" style="color:#999988;font-style:italic">;[3] 3rd occurrence of x </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 declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> x</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 car">list</span><span class="token plain"> old-x x</span><span class="token punctuation" style="color:#393A34">)</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 car">bar</span><span class="token plain"> ’first ’second</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 car">FIRST</span><span class="token plain"> SECOND</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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">few</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments argument variable" style="color:#36acaa">x</span><span class="token defun arguments"> </span><span class="token defun arguments other-marker-vars lisp-marker">&optional</span><span class="token defun arguments other-marker-vars"> </span><span class="token defun arguments other-marker-vars varform punctuation" style="color:#393A34">(</span><span class="token defun arguments other-marker-vars varform car">y</span><span class="token defun arguments other-marker-vars varform"> \*foo\*</span><span class="token defun arguments other-marker-vars varform punctuation" style="color:#393A34">)</span><span class="token defun 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 declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> \*foo\*</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 plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">The reference to \*foo\* in the first line of this example is not **special** even though there is a **special** declaration in the second line. </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">declaim</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> prosp</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> *! implementation-dependent* </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 keyword" style="color:#00009f">setq</span><span class="token plain"> prosp </span><span class="token number" style="color:#36acaa">1</span><span class="token plain"> reg </span><span class="token number" style="color:#36acaa">1</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> *!* </span><span class="token number" style="color:#36acaa">1</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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">prosp</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">2</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 car">reg</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">2</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 comment" style="color:#999988;font-style:italic">;the binding of prosp is special </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">set</span><span class="token plain"> ’prosp </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 car">set</span><span class="token plain"> ’reg </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 comment" style="color:#999988;font-style:italic">;due to the preceding proclamation, </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">list</span><span class="token plain"> prosp reg</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 comment" style="color:#999988;font-style:italic">;whereas the variable reg is lexical </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 number" style="color:#36acaa">3</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">2</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 car">list</span><span class="token plain"> prosp reg</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">1</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><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">declaim</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> x</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 comment" style="color:#999988;font-style:italic">;x is always special. </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 defun keyword" style="color:#00009f">defun</span><span class="token defun"> </span><span class="token defun function" style="color:#d73a49">example</span><span class="token defun"> </span><span class="token defun punctuation" style="color:#393A34">(</span><span class="token defun arguments argument variable" style="color:#36acaa">x</span><span class="token defun arguments"> </span><span class="token defun arguments argument variable" style="color:#36acaa">y</span><span class="token defun 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 declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> y</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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">y</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 car">x</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">\* x </span><span class="token number" style="color:#36acaa">2</span><span class="token punctuation" style="color:#393A34">)</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 car">print</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">+</span><span class="token plain"> y </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">locally</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> y</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> y</span><span class="token punctuation" style="color:#393A34">)</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">let</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">y</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">4</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 punctuation" style="color:#393A34">(</span><span class="token declare keyword" style="color:#00009f">declare</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">special</span><span class="token plain"> y</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 punctuation" style="color:#393A34">(</span><span class="token car">foo</span><span class="token plain"> x</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> *!* EXAMPLE </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">In the contorted code above, the outermost and innermost *bindings* of y are dynamic, but the middle binding is lexical. The two arguments to + are di↵erent, one being the value, which is 3, of the lexical variable y, and the other being the value of the dynamic variable named y </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">a</span><span class="token plain"> *binding* of which happens, coincidentally, to lexically surround it at an outer level</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain">. All the *bindings* of x and references to x are dynamic, however, because of the proclamation that x is always **special**. </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>
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<p><strong>See Also:</strong></p>
|
||
<p><span><b>defparameter</b></span>, <span><b>defvar</b></span></p>
|
||
<h2 class="anchor anchorWithStickyNavbar_LWe7" id="expanded-reference-special">Expanded Reference: special<a href="special_declaration.html#expanded-reference-special" class="hash-link" aria-label="Direct link to Expanded Reference: special" title="Direct link to Expanded Reference: special"></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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