two chars at once...

[Karl Heuer]

In article <11057 at smoke.BRL.MIL> gwyn at brl.arpa (Doug Gwyn) writes:
>In article <QZ3bmsW00WB4E5BEob at andrew.cmu.edu> sr16+ at 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 at haddock.isc.com), The Walking Lint