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Path: utzoo!mnetor!seismo!think!ima!haddock!karl
From: karl@haddock
Newsgroups: net.lang.c
Subject: Re: soundex algorithm wanted
Message-ID: <86900048@haddock>
Date: Mon, 8-Sep-86 17:16:00 EDT
Article-I.D.: haddock.86900048
Posted: Mon Sep  8 17:16:00 1986
Date-Received: Tue, 9-Sep-86 00:31:27 EDT
References: <3266@umcp-cs.UUCP>
Lines: 26
Nf-ID: #R:umcp-cs.UUCP:3266:haddock:86900048:000:1315
Nf-From: haddock!karl    Sep  8 17:16:00 1986


umcp-cs!chris (Chris Torek) writes:
>In article <1239@whuxl.UUCP> mike@whuxl.UUCP (BALDWIN) writes:
>>       register char   c, lc, prev = '0';
>All the compilers I have used ignore the `register' on `register char'
>declarations.

Well, the compilers I've used will put it in a register, but do extra work
(usually unnecessary) to clear the higher bits.  This is unfortunate.

>Is there ever any reason to declare a variable `register char' rather than
>`register int'?

If the range of the variable really is char (so EOF is excluded), then it
logically should be declared char.  I find it distasteful to write something
I don't mean just because it's more efficient than what I'd like*.  If the
machine has some one-byte registers available, `register char' is clearly a
good idea (assuming the compiler has any brains).  If the machine has only
full-word registers but allows byte access to them, `register char c0, c1,
c2, c3' could be packed into a single register; even on a VAX there are some
situations where the packing/unpacking cost is negligible (for non-numerical
usage, e.g.), and it saves on registers.  I don't know of any machines that
do this.

Karl W. Z. Heuer (ima!haddock!karl; karl@haddock.isc.com), The Walking Lint
*Like the keyword `register' itself, which is a crutch for dumb compilers.