37 lines
3.2 KiB
Rexx
37 lines
3.2 KiB
Rexx
/*REXX program using Knuth's algorithm S (a random sampling N of M items). */
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parse arg trials size . /*obtain optional arguments from the CL*/
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if trials=='' | trials=="," then trials= 100000 /*Not specified? Then use the default.*/
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if size=='' | size=="," then size= 3 /* " " " " " " */
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#.= 0 /*initialize frequency counter array. */
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do trials /*OK, now let's light this candle. */
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call s_of_n_creator size /*create an initial list of N items. */
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do gen=0 for 10; call s_of_n gen /*call s_of_n with a single decimal dig*/
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end /*gen*/
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/* [↓] examine what SofN generated. */
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do count=1 for size; _= !.count /*get a dec. digit from the Nth item. */
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#._= #._ + 1 /*bump counter for the decimal digit. */
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end /*count*/
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end /*trials*/
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@= ' trials, and with a size of '
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hdr= " Using Knuth's algorithm S for " commas(trials) @ || commas(size)": "
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say hdr; say copies("═", length(hdr) ) /*display the header and its separator.*/
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do dig=0 to 9 /* [↓] display the frequency of a dig.*/
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say right("frequency of the", 37) dig 'digit is: ' commas(#.dig)
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end /*dig*/
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exit /*stick a fork in it, we're all done. */
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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commas: parse arg _; do jc=length(_)-3 to 1 by -3; _=insert(',', _, jc); end; return _
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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s_of_n: parse arg item; items= items + 1 /*get "item", bump the items counter.*/
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if random(1, items)>size then return /*probability isn't good, so skip it. */
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_= random(1, size); !._= item /*now, figure out which previous ··· */
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return /* ··· item to replace with ITEM.*/
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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s_of_n_creator: parse arg item 1 items /*generate ITEM number of items. */
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do k=1 for item /*traipse through the first N items. */
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!.k= random(0, 9) /*set the Kth item with random digit.*/
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end /*k*/
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return /*the piddly stuff is done (for now). */
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