65 lines
4.4 KiB
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65 lines
4.4 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: Variable *RANDOM-STATE*</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_rnd_st.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_nump.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="STrandom-stateST"><I>Variable</I> <B>*RANDOM-STATE*</B></A> <P>
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<P><B>Value Type:</B><P>
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<P>
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a <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A>. <P>
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<P><B>Initial Value:</B><P>
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<P>
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<A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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The <A REL=DEFINITION HREF="26_glo_c.htm#current_random_state"><I>current random state</I></A>, which is used, for example, by the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_random.htm#random"><B>random</B></A> when a <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A> is not explicitly supplied. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(random-state-p *random-state*) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(setq snap-shot (make-random-state))
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;; The series from any given point is random,
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;; but if you backtrack to that point, you get the same series.
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(list (loop for i from 1 to 10 collect (random))
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(let ((*random-state* snap-shot))
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(loop for i from 1 to 10 collect (random)))
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(loop for i from 1 to 10 collect (random))
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(let ((*random-state* snap-shot))
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(loop for i from 1 to 10 collect (random))))
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=> ((19 16 44 19 96 15 76 96 13 61)
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(19 16 44 19 96 15 76 96 13 61)
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(16 67 0 43 70 79 58 5 63 50)
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(16 67 0 43 70 79 58 5 63 50))
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B><P>
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<P>
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The <A REL=DEFINITION HREF="26_glo_i.htm#implementation"><I>implementation</I></A>. <P>
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<A REL=DEFINITION HREF="f_random.htm#random"><B>random</B></A>. <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_mk_rnd.htm#make-random-state"><B>make-random-state</B></A>, <A REL=DEFINITION HREF="f_random.htm#random"><B>random</B></A>, <A REL=DEFINITION HREF="t_rnd_st.htm#random-state"><B>random-state</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="26_glo_b.htm#binding"><I>Binding</I></A> <A REL=DEFINITION HREF="#STrandom-stateST"><B>*random-state*</B></A> to a different <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> correctly saves and restores the old <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. <P>
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