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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: "C's Biggest Mistake"
Date: Sat, 07 Apr 2018 13:13:25 -0700
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David Brown <david.brown@hesbynett.no> writes:
[...]
> But that would be a very weird way to write the code in C.  Why would 
> you have a switch here?
>
> 	while (true) {
> 		c = *p++;
> 		if ((c >= 'A') && (c <= 'Z)) continue;
> 		if ((c >= '0') && (c <= '9)) continue;
> 		break;
> 	}
>
> (There are many other ways to write it - that was just one example.)
[...]

Both your version and bartc's example (in his own language) using
ranges are non-portable.  The language guarantees that '0'..'9' are
contiguous, but it makes no such guarantee for 'A'..'Z' or 'a'..'z'.
And in fact in EBCDIC there are extra characters between 'A' and
'Z', and between 'a' and 'z'.

(And depending on the application you might need to deal with
letters other than the 52 Latin ones.)

Incidentally, gcc supports case ranges as an extension, but it uses
`...` rather than `..` (probably because `...` is an existing token).
And the documentation warns the programmer to put spaces around the
`...` symbol, because  `1...5` would fail to parse.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"