65 lines
4.6 KiB
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65 lines
4.6 KiB
HTML
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<TITLE>CLHS: Function RANDOM</TITLE>
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<A NAME="random"><I>Function</I> <B>RANDOM</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>random</B> <I>limit <TT>&optional</TT> random-state</I> => <I>random-number</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>limit</I>---a positive <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>, or a positive <A REL=DEFINITION HREF="26_glo_f.htm#float"><I>float</I></A>. <P>
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<I>random-state</I>---a <A REL=DEFINITION HREF="26_glo_r.htm#random_state"><I>random state</I></A>. The default is the <A REL=DEFINITION HREF="26_glo_c.htm#current_random_state"><I>current random state</I></A>. <P>
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<I>random-number</I>---a non-negative <A REL=DEFINITION HREF="26_glo_n.htm#number"><I>number</I></A> less than <I>limit</I> and of the same <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> as <I>limit</I>. <P>
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<P><B>Description:</B><P>
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<P>
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Returns a pseudo-random number that is a non-negative <A REL=DEFINITION HREF="26_glo_n.htm#number"><I>number</I></A> less than <I>limit</I> and of the same <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> as <I>limit</I>. <P>
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The <I>random-state</I>, which is modified by this function, encodes the internal state maintained by the random number generator. <P>
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An approximately uniform choice distribution is used. If <I>limit</I> is an <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A>, each of the possible results occurs with (approximate) probability 1/<I>limit</I>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(<= 0 (random 1000) 1000) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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(let ((state1 (make-random-state))
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(state2 (make-random-state)))
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(= (random 1000 state1) (random 1000 state2))) => <A REL=DEFINITION HREF="26_glo_t.htm#true">true</A>
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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The <I>random-state</I> is modified. <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>limit</I> is not a positive <A REL=DEFINITION HREF="26_glo_i.htm#integer"><I>integer</I></A> or a positive <A REL=DEFINITION HREF="t_real.htm#real"><I>real</I></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="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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See <I>Common Lisp: The Language</I> for information about generating random numbers. <P>
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