64 lines
4 KiB
HTML
64 lines
4 KiB
HTML
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function NOT</TITLE>
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<A NAME="not"><I>Function</I> <B>NOT</B></A> <P>
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<P>
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<P><B>Syntax:</B><P>
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<P>
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<B>not</B> <I>x</I> => <I>boolean</I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>x</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A> (i.e., any <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>). <P>
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<I>boolean</I>---a <A REL=DEFINITION HREF="26_glo_b.htm#boolean"><I>boolean</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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Returns <A REL=DEFINITION HREF="a_t.htm#t"><B>t</B></A> if <I>x</I> is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>; otherwise, returns <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(not nil) => T
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(not '()) => T
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(not (integerp 'sss)) => T
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(not (integerp 1)) => NIL
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(not 3.7) => NIL
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(not 'apple) => NIL
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</PRE>
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</TT> <P>
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<P>
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<P><B>Side Effects:</B> None.
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<P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B> None.
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<P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f_null.htm#null"><B>null</B></A> <P>
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<P><B>Notes:</B><P>
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<P>
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<A REL=DEFINITION HREF="#not"><B>not</B></A> is intended to be used to invert the `truth value' of a <A REL=DEFINITION HREF="26_glo_b.htm#boolean"><I>boolean</I></A> (or <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>) whereas <A REL=DEFINITION HREF="f_null.htm#null"><B>null</B></A> is intended to be used to test for the <A REL=DEFINITION HREF="26_glo_e.htm#empty_list"><I>empty list</I></A>. Operationally, <A REL=DEFINITION HREF="#not"><B>not</B></A> and <A REL=DEFINITION HREF="f_null.htm#null"><B>null</B></A> compute the same result; which to use is a matter of style. <P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss249.htm">NOT-AND-NULL-RETURN-VALUE:X3J13-MAR-93</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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