75 lines
5.8 KiB
HTML
75 lines
5.8 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 MAKE-RANDOM-STATE</TITLE>
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<A NAME="make-random-state"><I>Function</I> <B>MAKE-RANDOM-STATE</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>make-random-state</B> <I><TT>&optional</TT> state</I> => <I>new-state</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>state</I>---a <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A>, or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, or <A REL=DEFINITION HREF="a_t.htm#t"><B>t</B></A>. The default is <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<I>new-state</I>---a <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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<P><B>Description:</B><P>
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<P>
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Creates a <A REL=DEFINITION HREF="26_glo_f.htm#fresh"><I>fresh</I></A> <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="t_rnd_st.htm#random-state"><B>random-state</B></A> suitable for use as the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of <A REL=DEFINITION HREF="v_rnd_st.htm#STrandom-stateST"><B>*random-state*</B></A>. <P>
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If <I>state</I> is a <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>, the <I>new-state</I> is a <A REL=DEFINITION HREF="26_glo_c.htm#copy"><I>copy</I></A>[5] of that <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. If <I>state</I> is <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, the <I>new-state</I> is a <A REL=DEFINITION HREF="26_glo_c.htm#copy"><I>copy</I></A>[5] of the <A REL=DEFINITION HREF="26_glo_c.htm#current_random_state"><I>current random state</I></A>. If <I>state</I> is <A REL=DEFINITION HREF="a_t.htm#t"><B>t</B></A>, the <I>new-state</I> is a <A REL=DEFINITION HREF="26_glo_f.htm#fresh"><I>fresh</I></A> <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> that has been randomly initialized by some means. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(let* ((rs1 (make-random-state nil))
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(rs2 (make-random-state t))
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(rs3 (make-random-state rs2))
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(rs4 nil))
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(list (loop for i from 1 to 10
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collect (random 100)
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when (= i 5)
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do (setq rs4 (make-random-state)))
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(loop for i from 1 to 10 collect (random 100 rs1))
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(loop for i from 1 to 10 collect (random 100 rs2))
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(loop for i from 1 to 10 collect (random 100 rs3))
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(loop for i from 1 to 10 collect (random 100 rs4))))
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=> ((29 25 72 57 55 68 24 35 54 65)
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(29 25 72 57 55 68 24 35 54 65)
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(93 85 53 99 58 62 2 23 23 59)
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(93 85 53 99 58 62 2 23 23 59)
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(68 24 35 54 65 54 55 50 59 49))
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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>state</I> is not a <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A>, or <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, or <A REL=DEFINITION HREF="a_t.htm#t"><B>t</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_random.htm#random"><B>random</B></A>, <A REL=DEFINITION HREF="v_rnd_st.htm#STrandom-stateST"><B>*random-state*</B></A> <P>
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<P><B>Notes:</B><P>
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<P>
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One important use of <A REL=DEFINITION HREF="#make-random-state"><B>make-random-state</B></A> is to allow the same series of pseudo-random <A REL=DEFINITION HREF="26_glo_n.htm#number"><I>numbers</I></A> to be generated many times within a single program. <P>
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