Path: utzoo!utgpu!attcan!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.uucp (Richard A. O'Keefe)
Newsgroups: comp.lang.c
Subject: Re: getch() and getche() in MSC 4.0
Message-ID: <561@quintus.UUCP>
Date: 22 Oct 88 03:32:29 GMT
References: <10508@dartvax.Dartmouth.EDU> <7594@bloom-beacon.MIT.EDU>
Sender: news@quintus.UUCP
Reply-To: ok@quintus.UUCP (Richard A. O'Keefe)
Organization: Quintus Computer Systems, Inc.
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In article <7594@bloom-beacon.MIT.EDU> scs@adam.pika.mit.edu (Steve Summit) writes:
>This is a snide, whiney "I told you so" to the efficiency addicts
>and macro panderers out there.
>
>	#define _toupper(c)  ((c) - ('a' - 'A'))
>	#define toupper(c) (islower(c) ? _toupper(c) : (c))
>
>If it is desirable for toupper to work correctly on characters
>that are nonalphabetic or already upper-case (I believe this
>property is called "idempotence," and as I said, it is a laudable
>goal), then the macro implementation has to be sacrificed, and
>toupper() made a proper function.

This conclusion does not follow.  *THAT* version of toupper() has to
go, but you can still usefully use a macro.

	extern char _utab[];
	#define toupper(c) _utab[(c) & 255]

Merits:	(1) single evaluation
	(2) usually faster than a function call
	(3) works nicely with EBCDIC or ISO 8859, not just ASCII

This is a good way of turning any function-from-characters into a macro:
compute all the function values when your program starts and store them
in an array.  (Look at the is<class>() macros in /usr/include/ctype.h .)