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53 lines
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<TITLE>CLHS: Section 3.1</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_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="03_.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="03_aa.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 Evaluation</H2> <P>
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<I>Execution</I> of <A REL=DEFINITION HREF="26_glo_c.htm#code"><I>code</I></A> can be accomplished by a variety of means ranging from direct interpretation of a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> representing a <A REL=DEFINITION HREF="26_glo_p.htm#program"><I>program</I></A> to invocation of <A REL=DEFINITION HREF="26_glo_c.htm#compiled_code"><I>compiled code</I></A> produced by a <A REL=DEFINITION HREF="26_glo_c.htm#compiler"><I>compiler</I></A>. <P>
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<A REL=DEFINITION HREF="26_glo_e.htm#evaluation"><I>Evaluation</I></A> is the process by which a <A REL=DEFINITION HREF="26_glo_p.htm#program"><I>program</I></A> is <I>executed</I> in Common Lisp. The mechanism of <A REL=DEFINITION HREF="26_glo_e.htm#evaluation"><I>evaluation</I></A> is manifested both implicitly through the effect of the <A REL=DEFINITION HREF="26_glo_l.htm#lisp_read-eval-print_loop"><I>Lisp read-eval-print loop</I></A>, and explicitly through the presence of the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>functions</I></A> <A REL=DEFINITION HREF="f_eval.htm#eval"><B>eval</B></A>, <A REL=DEFINITION HREF="f_cmp.htm#compile"><B>compile</B></A>, <A REL=DEFINITION HREF="f_cmp_fi.htm#compile-file"><B>compile-file</B></A>, and <A REL=DEFINITION HREF="f_load.htm#load"><B>load</B></A>. Any of these facilities might share the same execution strategy, or each might use a different one. <P>
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The behavior of a <A REL=DEFINITION HREF="26_glo_c.htm#conforming_program"><I>conforming program</I></A> processed by <A REL=DEFINITION HREF="f_eval.htm#eval"><B>eval</B></A> and by <A REL=DEFINITION HREF="f_cmp_fi.htm#compile-file"><B>compile-file</B></A> might differ; see <A REL=CHILD HREF="03_bbc.htm">Section 3.2.2.3 (Semantic Constraints)</A>. <P>
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<A REL=DEFINITION HREF="26_glo_e.htm#evaluation"><I>Evaluation</I></A> can be understood in terms of a model in which an interpreter recursively traverses a <A REL=DEFINITION HREF="26_glo_f.htm#form"><I>form</I></A> performing each step of the computation as it goes. This model, which describes the semantics of Common Lisp <A REL=DEFINITION HREF="26_glo_p.htm#program"><I>programs</I></A>, is described in <A REL=CHILD HREF="03_ab.htm">Section 3.1.2 (The Evaluation Model)</A>. <P>
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<A REL=CHILD HREF="03_aa.htm"><H2>
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3.1.1 Introduction to Environments</H2></A><P>
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<A REL=CHILD HREF="03_ab.htm"><H2>
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3.1.2 The Evaluation Model</H2></A><P>
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<A REL=CHILD HREF="03_ac.htm"><H2>
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3.1.3 Lambda Expressions</H2></A><P>
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<A REL=CHILD HREF="03_ad.htm"><H2>
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3.1.4 Closures and Lexical Binding</H2></A><P>
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<A REL=CHILD HREF="03_ae.htm"><H2>
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3.1.5 Shadowing</H2></A><P>
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<A REL=CHILD HREF="03_af.htm"><H2>
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3.1.6 Extent</H2></A><P>
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<A REL=CHILD HREF="03_ag.htm"><H2>
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3.1.7 Return Values</H2></A><P><HR>
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