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From: gwyn@smoke.brl.mil (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: missing ->= operator
Message-ID: <16024@smoke.brl.mil>
Date: 1 May 91 19:09:22 GMT
References: <9104291641.AA00534@dutiaa.tudelft.nl> <1991Apr30.165110.4165@unhd.unh.edu>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 25

In article <1991Apr30.165110.4165@unhd.unh.edu> jwm712@unhd.unh.edu (Jonathan W Miner) writes:
>It is my opinion that the +=, &= etc operators were implemented on systems,
>such as DEC VAX that has two operand instructions.  Although it would
>be nice to have a ->=, it would be a programmer convenience, and it would
>still be compiled into the same code as p = p->next.  

No, you're not supposed to be thinking about what code is going to be
generated.

The main advantage of op= occurs in situations like:

	p->link->data[BIG_ROOM].flags |= BEEN_HERE;

where it would be tedious and error-prone to have to duplicate the LHS
as an operand, which would be necessary if the op= form did not exist.

There is no such justification for ->=, which seldom would be used in
contexts more involved than

	p = p->next;

which is easy enough to code as is.

There are some other more technical reasons involving type compatibility,
etc. but the above argument shows that it is not worth doing.