68 lines
4.7 KiB
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68 lines
4.7 KiB
HTML
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<!-- 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 LOGBITP</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="f_logand.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_number.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_logcou.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<HR>
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<A NAME="logbitp"><I>Function</I> <B>LOGBITP</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>logbitp</B> <I>index integer</I> => <I>generalized-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>index</I>---a non-negative <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>. <P>
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<I>integer</I>---an <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>. <P>
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<I>generalized-boolean</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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<A REL=DEFINITION HREF="#logbitp"><B>logbitp</B></A> is used to test the value of a particular bit in <I>integer</I>, that is treated as if it were binary. The value of <A REL=DEFINITION HREF="#logbitp"><B>logbitp</B></A> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A> if the bit in <I>integer</I> whose index is <I>index</I> (that is, its weight is 2^<I>index</I>) is a one-bit; otherwise it is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>. <P>
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Negative <I>integers</I> are treated as if they were in two's-complement notation. <P>
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<P><B>Examples:</B><P>
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<PRE>
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(logbitp 1 1) => <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
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(logbitp 0 1) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(logbitp 3 10) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(logbitp 1000000 -1) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(logbitp 2 6) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(logbitp 0 6) => <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
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</PRE>
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</TT> <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><P>
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<P>
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Should signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>index</I> is not a non-negative <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>. Should signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>integer</I> is not an <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>. <P>
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<P><B>See Also:</B> None.
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<P>
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<P><B>Notes:</B><P>
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<P>
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<PRE>
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(logbitp k n) == (ldb-test (byte 1 k) n)
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</PRE>
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</TT> <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/iss013.htm">ARGUMENTS-UNDERSPECIFIED:SPECIFY</A><P></UL><HR>
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