Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!ginosko!uunet!fernwood!decwrl!decvax!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: two chars at once...
Message-ID: <14639@haddock.ima.isc.com>
Date: 19 Sep 89 00:10:31 GMT
References: <QZ3bmsW00WB4E5BEob@andrew.cmu.edu> <11057@smoke.BRL.MIL>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 23

In article <11057@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn) writes:
>In article <QZ3bmsW00WB4E5BEob@andrew.cmu.edu> sr16+@andrew.cmu.edu (Seth Benjamin Rothenberg) writes:
>>One of the nasty things it does is treat 2 characters
>>as a single 2-byte integer.
>>	if  "ax" = mystr    ->  if mystr[1]=>C1D9  (or something like that)
>
>The direct equivalent in C would be to use multi-character character
>constants such as 'AX', which [contain both characters in an implementation-
>dependent manner].  Using 2-character strings would be more portable

(Terminology: since X3J11 has already claimed the words "multibyte character"%
and "wide character"&, and neither one of them refers to the construct above,
I have taken to calling them "siamese character constants".)

If the inefficiency of using two-character strings is a problem, and you don't
want to rely on the properties (or even the existence) of siamese character
constants, you can replace them with a macro:
	#define two(a,b) (((a)<<CHAR_BIT)|(b))
	if (two('a','x') == mystr) ...
(It doesn't matter whether two() is defined as above or the other way around,
as long as it's consistent.)

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint