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From: ath@helios.prosys.se (Anders Thulin)
Newsgroups: comp.os.minix
Subject: Re: A simple question
Message-ID: <405@helios.prosys.se>
Date: 29 Mar 89 06:30:24 GMT
References: <11762@louie.udel.EDU>
Organization: Programsystem AB, Linkoping, SWEDEN
Lines: 26

In article <11762@louie.udel.EDU> PL147744%TECMTYVM.BITNET@uicvm.uic.edu (Marcela Bonilla J.) writes:
>Can anybody tell me what does this instruccion means ?
>
>" r = (rp - proc) - NR_TASKS  "
>
>rp is a pointer to a structure of type proc and proc is the table of
>procedures... =)

Quote:

	"If two pointers to objects of the same type are subtracted,
	the result is converted (by division by the length of the
	object) to an int representing the number of objects
	separating the pointed-to objects.  The conversion will in
	general give unexpected results, unless the pointers point to
	objects in the same array, since pointers, even to objects of
	the same type, do not necessarily differ by a multiple of the
	object length"

(rp - proc) produces the index of rp inside the table proc, that
is rp == proc[rp-proc].
-- 
Anders Thulin			INET : ath@prosys.se
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