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<TITLE>CLHS: Section 3.1.2.1.2.1</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="03_abab.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="03_abab.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="03_ababb.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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3.1.2.1.2.1 Special Forms</H2> <P>
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A <A REL=DEFINITION HREF="26_glo_s.htm#special_form"><I>special form</I></A> is a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> with special syntax, special evaluation rules, or both, possibly manipulating the evaluation environment, control flow, or both. A <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operator</I></A> has access to the current <A REL=DEFINITION HREF="26_glo_l.htm#lexical_environment"><I>lexical environment</I></A> and the current <A REL=DEFINITION HREF="26_glo_d.htm#dynamic_environment"><I>dynamic environment</I></A>. Each <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operator</I></A> defines the manner in which its <A REL=DEFINITION HREF="26_glo_s.htm#subexpression"><I>subexpressions</I></A> are treated---which are <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>forms</I></A>, which are special syntax, <I>etc</I>. <P>
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Some <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operators</I></A> create new lexical or dynamic <A REL=DEFINITION HREF="26_glo_e.htm#environment"><I>environments</I></A> for use during the <A REL=DEFINITION HREF="26_glo_e.htm#evaluation"><I>evaluation</I></A> of <A REL=DEFINITION HREF="26_glo_s.htm#subform"><I>subforms</I></A> of the <A REL=DEFINITION HREF="26_glo_s.htm#special_form"><I>special form</I></A>. For example, <A REL=DEFINITION HREF="s_block.htm#block"><B>block</B></A> creates a new <A REL=DEFINITION HREF="26_glo_l.htm#lexical_environment"><I>lexical environment</I></A> that is the same as the one in force at the point of evaluation of the <A REL=DEFINITION HREF="s_block.htm#block"><B>block</B></A> <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> with the addition of a <A REL=DEFINITION HREF="26_glo_b.htm#binding"><I>binding</I></A> of the <A REL=DEFINITION HREF="s_block.htm#block"><B>block</B></A> name to an <A REL=DEFINITION HREF="26_glo_e.htm#exit_point"><I>exit point</I></A> from the <A REL=DEFINITION HREF="s_block.htm#block"><B>block</B></A>. <P>
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The set of <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operator</I></A> <A REL=DEFINITION HREF="26_glo_n.htm#name"><I>names</I></A> is fixed in Common Lisp; no way is provided for the user to define a <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operator</I></A>. The next figure lists all of the Common Lisp <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbols</I></A> that have definitions as <A REL=DEFINITION HREF="26_glo_s.htm#special_operator"><I>special operators</I></A>. <P>
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<A NAME="clspecialops"> <PRE>
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<A REL=DEFINITION HREF="s_block.htm#block">block</A> <A REL=DEFINITION HREF="s_let_l.htm#letST">let*</A> <A REL=DEFINITION HREF="s_ret_fr.htm#return-from">return-from</A>
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<A REL=DEFINITION HREF="s_catch.htm#catch">catch</A> <A REL=DEFINITION HREF="s_ld_tim.htm#load-time-value">load-time-value</A> <A REL=DEFINITION HREF="s_setq.htm#setq">setq</A>
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<A REL=DEFINITION HREF="s_eval_w.htm#eval-when">eval-when</A> <A REL=DEFINITION HREF="s_locall.htm#locally">locally</A> <A REL=DEFINITION HREF="s_symbol.htm#symbol-macrolet">symbol-macrolet</A>
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<A REL=DEFINITION HREF="s_flet_.htm#flet">flet</A> <A REL=DEFINITION HREF="s_flet_.htm#macrolet">macrolet</A> <A REL=DEFINITION HREF="s_tagbod.htm#tagbody">tagbody</A>
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<A REL=DEFINITION HREF="a_fn.htm#function">function</A> <A REL=DEFINITION HREF="s_multip.htm#multiple-value-call">multiple-value-call</A> <A REL=DEFINITION HREF="s_the.htm#the">the</A>
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<A REL=DEFINITION HREF="s_go.htm#go">go</A> <A REL=DEFINITION HREF="s_mult_1.htm#multiple-value-prog1">multiple-value-prog1</A> <A REL=DEFINITION HREF="s_throw.htm#throw">throw</A>
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<A REL=DEFINITION HREF="s_if.htm#if">if</A> <A REL=DEFINITION HREF="s_progn.htm#progn">progn</A> <A REL=DEFINITION HREF="s_unwind.htm#unwind-protect">unwind-protect</A>
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<A REL=DEFINITION HREF="s_flet_.htm#labels">labels</A> <A REL=DEFINITION HREF="s_progv.htm#progv">progv</A>
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<A REL=DEFINITION HREF="s_let_l.htm#let">let</A> <A REL=DEFINITION HREF="s_quote.htm#quote">quote</A>
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</PRE>
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<P><B>Figure 3-2. Common Lisp Special Operators</B></A> <P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss181.htm">GENERIC-FLET-POORLY-DESIGNED:DELETE</A><LI> <A REL=CHILD HREF="../Issues/iss216.htm">LOAD-TIME-EVAL:R**2-NEW-SPECIAL-FORM</A><LI> <A REL=CHILD HREF="../Issues/iss359.htm">WITH-ADDED-METHODS:DELETE</A><LI> <A REL=CHILD HREF="../Issues/iss066.htm">COMPILER-LET-CONFUSION:ELIMINATE</A><P></UL><HR>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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