On Wed, Apr 08, 2009 at 06:55:12PM +0100, lostgallifreyan wrote:
> Joshua Phillips <jp.sittingd...@gmail.com> wrote:
> >For case-insensitive comparisons in C, there's strcasecmp (GNU) and stricmp
> >(MSVCRT). They're both identical in function, but are non-standard
> >extensions.
>
> No generic case comparion OR forcing in C?
Not for complete strings. There are case-folding functions for
individual characters, and you can trivially case-fold a string by
iterating over its content. Something like this, perhaps:
for (unsigned char * p = s;*p != '\0';p++)
*p = tolower(*p);
> Lua is based in C
Lua's "string.upper" function constructs a new string by calling C's
"toupper" function on each of the original string's characters. The
"string.lower" function does the same thing using "tolower".
Aside: C also has case-folding functions for wide characters, but they
probably aren't sufficient to handle Unicode because they just have
single characters as input and output. Unicode's case folding
algorithms sometimes change the string length. For example the German
sharp-s is a single character in lower case but two characters in
upper case, and Greek has even more complex conversions.
There's also the issue that some letters fold differently based on the
source language. C's locale support might be able to deal with this
if you adjust the locale to match the text being processed (rather
than the user environment). For example the case conversions for "i"
and "I" are different in Turkish than in English. In one bizarre
situation, using the English conversions on some Turkish text
apparently set off a chain of events leading to multiple homicides:
http://www.gizmodo.com.au/2008/04/a_cellphones_missing_dot_kills_two_people_puts_three_more_in_jail-2.html
-Dave Dodge
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