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From: wutcd@chemnitz.guug.de (Joerg Wunsch)
Subject: Re: 386BSD's non-standard C library
Message-ID: <wutcd.718395968@hadrian>
Sender: bin@hrz.tu-chemnitz.de (Owner of all binaries)
Organization: tu-chemnitz
References: <1992Sep24.031603.21009@minyos.xx.rmit.oz.au> <wutcd.717452137@hadrian> <1992Oct04.090410.26720@am.sublink.org>
Date: Tue, 6 Oct 1992 18:26:08 GMT
Lines: 35
alex@am.sublink.org (Alex Martelli) writes:
>...
>I once benchmarked the is*() and to*() functions from ctype.h as macros
>using table-lookup instead and got huge speedups... that was in some PC
>C compiler long ago, but I believe a simple lookup will still be
>superior to a comparison, if and addition, and you need only pay a
>few hundred bytes (256 each for toupper(), tolower(), and is*() since
>the latter can make do with 1 byte/char by using the bits as flags for
>lowercase, uppercase, digit, etc, for example isalnum() will do the
>lookup and & the flag byte with (ISLOWER|ISUPPER|ISDIGIT)).
>--
Ooops, you are not right, i guess. The macros _and_ the functions all
do a table lookup (btw: the tables are smaller, only 2 * (256 + 1) bytes;
i.e. for each char + for EOF one byte for the is*()-flags, and one byte
for to{upper,lower}() ). But the problem is still another: if i had
a given string ``FOO'', it'd be obvious: tolower()ing it must result in
``foo'' - but i can write down this immediate without any function or
macro calls:-) If i don't know which characters my string consists of,
but my intent is to have all possible uppercase characters in lower case,
i'd _always_ habe to test for isupper(). So why shouldn't do that the
tolower() function/macro?
ANNOUNCEMENT: my enhanced ctype(3) package is complete now. That would
be especially of interest for European people. It is based on configur-
able character classes as done in SVR3. I'm only awaiting the test re-
port of an alpha tester before releasing it.
Enjoy, J"org
--
J"org Wunsch, TCD GmbH Dresden, R"ahnitzgasse 18, D-O-8060 Dresden
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