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From: ahby@meccts.MECC.MN.ORG (Shane P. McCarron)
Newsgroups: comp.sys.apple
Subject: Re: FRE
Message-ID: <2746@meccts.MECC.MN.ORG>
Date: Wed, 13-May-87 14:48:42 EDT
Article-I.D.: meccts.2746
Posted: Wed May 13 14:48:42 1987
Date-Received: Sat, 16-May-87 07:32:01 EDT
References: <8705052345.AA17994@cdfb.toronto.edu> <153@genat.UUCP>
Reply-To: ahby@meccts.UUCP (Shane P. McCarron)
Distribution: world
Organization: MECC Technical Services, St. Paul, MN
Lines: 35


In article <153@genat.UUCP>:
>FRE(0) will give free space
>FRE(" ") will force garbage collection and then give free space
>
>There is a difference!

I am looking at the FRE code, and it reads:

fre	lda	valtyp	
	beq	fre1		; if not a string
	jsr	frestrE		; frestrE frees up tmp
fre1	jsr	garbag
	sec
	lda	fretop		; figure out free space
	sbc	strend
	tay
	lda	fretop+1
	sbc	strend+1	; and fall into givayf

Valtyp is 0 if a numeric, 0xff if a string.  FrestrE is a secondary
entry point in frestr that assumes there is a string.  Frestr falls 
into fretmp, which will adjust fretop if the temporary string 
(" " in this case) is the last string in memory.  Since it is most
assuredly the last string in memory, fretop will be adjusted.  However, it
would never have been moved down if a string hadn't been used in the
fre() call, so that may not be a great adantage.

Regardless of what the argument is, fre executes garbag, which forces
a garbage collect.
-- 
Shane P. McCarron		UUCP	ihnp4!meccts!ahby, ahby@MECC.MN.ORG
MECC Technical Services		ATT	(612) 481-3589
(C) Copyright 1987 Shane P. McCarron
	Redistribution allowed only if your recipients can redistribute