63 lines
1.7 KiB
HTML
63 lines
1.7 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Originally converted to HTML using LaTeX2HTML 95 (Thu Jan 19 1995) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE> eval (FUNCTION)</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" eval (FUNCTION)">
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<meta name="keywords" value="lp">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<BR> <HR>
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<A HREF="node94.html"><IMG ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A>
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<A HREF="node72.html"><IMG ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A>
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<A HREF="node92.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif"></A> <BR>
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<A HREF="lp.html"><B>Contents</B></A>
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<B> Next:</B>
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<A HREF="node94.html"> evenpoddp (PREDICATES)</A>
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<B>Up:</B>
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<A HREF="node72.html"> Appendix: Selected Lisp </A>
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<B> Previous:</B>
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<A HREF="node92.html"> eql (PREDICATE)</A>
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<BR> <HR> <P>
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<H1> eval (FUNCTION)</H1>
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<P>
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<b> Format:</b>
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<tt> (eval <exp> )</tt>
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<P>
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<b> Required arguments:</b>
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1
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<P>
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<tt> <exp> </tt>: any Lisp expression.
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<P>
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eval provides direct access to the Lisp expression evaluator. It causes the evaluation of whatever <tt> <exp> </tt> returns. Thus, if <tt> <exp> </tt> is an evaluable Lisp expression that returns an evaluable Lisp expression, then eval returns the value of evaluating this second expression.
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<P>
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<b> Examples:</b>
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<P>
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<BLOCKQUOTE>
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<PRE>> (eval '(+ 1 2))
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3
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> (eval (cons '+ '(1 2)))
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3
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> (eval 3)
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3
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> (eval (+ 3 4))
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7
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> (eval (cons 'a '(s d f)))
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Error: The function A is undefined.
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</PRE>
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</BLOCKQUOTE>
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<P>
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<BR> <HR>
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<P>
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<ADDRESS>
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<I>© Colin Allen & Maneesh Dhagat <BR>
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March 2007 </I>
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</ADDRESS>
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</BODY>
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