Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!lsr
From: lsr@Apple.COM (Larry Rosenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Random help, please
Message-ID: <549@internal.Apple.COM>
Date: 6 Feb 89 22:53:47 GMT
References: <69823DN5@PSUVM> <2671@munnari.oz>
Organization: Advanced Technology Group, Apple Computer
Lines: 29

In article <2671@munnari.oz> jkjl@munnari.UUCP (John Lim) writes:
>In article <69823DN5@PSUVM> DN5@PSUVM.BITNET writes:

>>  I am working on a DA which needs some random numbers.  My problem is that
>>I always get the same sequence.  I have tried setting randSeed, but this
>
>	You just cannot simply reset randSeed in C by :
>
>		randSeed = TickCount();
>
>	because LSC thinks that randSeed is a DA global offset by A4 and
>	not A5 (which is what u want).

randSeed happens to be a Quickdraw global variable.  A5 always points to a
pointer to the Quickdraw variables.  I think assembly code such as:

	MOVE.L	(A5),A0
	MOVE.L	randSeed(A0),D0

will get randSeed.  From the MPW assembler interfaces, it looks like
randSeed is -$7E.  Looking at the code for _Random in Macsbug seems to
confirm this.


-- 
		 Larry Rosenstein,  Object Specialist
 Apple Computer, Inc.  20525 Mariani Ave, MS 46-B  Cupertino, CA 95014
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