Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!snorkelwacker!mit-eddie!bu.edu!dartvax!eleazar.dartmouth.edu!llama
From: llama@eleazar.dartmouth.edu (Joseph A. Francis)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Random number Generator wanted.
Message-ID: <22950@dartvax.Dartmouth.EDU>
Date: 28 Jun 90 20:43:06 GMT
References: <152@asacsg.mh.nl> <47XL38V@xavier.swarthmore.edu>
Sender: news@dartvax.Dartmouth.EDU
Organization: Dartmouth College, Hanover, NH
Lines: 35

In article <47XL38V@xavier.swarthmore.edu> jackiw@cs.swarthmore.edu (Nick Jackiw) writes:
->kr@asacsg.mh.nl (Koos Remigius) writes:
->.> This function gives me a random integer ( between 0 and range ). 
->.> function Randomize(range:Integer):Integer;
->.> var
->.>   rawResult:LongInt;
->.>   begin  { Randomize }		
->.>     rawResult:=(ABS(Random);
->.>     Randomize:=(rawResult * range) div 32768;{ Scale to specified range }
->.>   end;    { Randomize }
->
->----------
->Much more efficient: Randomize:=abs(random) mod succ(range);
->----------

Actually, this may be a dangerous "optimization".  Many random number
generators yeild numbers which are evenly DISTRIBUTED, but which in 
other ways are non-random.  One very widely used random number generation
algorithm generates numbers wholes last digits cycle repeatedly through
the same values (in decimal).  So, for instance, if you are looking for 
random numbers in the range 0-9 (pretty common!) you will continually get the
same cycle of digits back if you use MOD.  If you use DIV, the results will
have the same overall "randomness" as the raw numbers returned by the 
random function.

>> Greetings from Holland,
>> Koos Remigius.
>
>Regards from Philadelphia.

Hubba hubbas from Hanover.
Joe Francis

----------------------------------------------------------------------------
"Read my Lips: No Nude Texans!" - George Bush, clarifying a misunderstanding