Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Definition of boolean type
Message-ID: <15906@mimsy.UUCP>
Date: 11 Feb 89 02:39:31 GMT
References: <10@dbase.UUCP> <9609@smoke.BRL.MIL> <3645@arcturus>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

In article <3645@arcturus> evil@arcturus.UUCP (Wade Guthrie) writes:
>Why make a simple idea more complicated?

Indeed.

Perhaps the biggest problem with boolean types, and definitions for
`TRUE' and `FALSE' (or True and False or true and false or . . .)
is exemplified by the QDSS driver supplied with 4.3BSD-tahoe (for
which no one at Berkeley is at fault).  It had the following definitions
(somewhat paraphrased):

	#define FALSE 0
	#define TRUE ~FALSE
	...
	/* these macros return TRUE when the queue is empty/full/... */
	#define ISEMPTY(eq) ((eq)->head.foo == (eq)->tail.foo)

The code then read

		if (ESEMPTY(eq) == TRUE) bar();

It is left as an exercise to the reader to determine why this test
will never call function bar().
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris