Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!uxc!uxc.cso.uiuc.edu!uxg.cso.uiuc.edu!uxe.cso.uiuc.edu!mcdonald
From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: Definition of boolean type
Message-ID: <225800128@uxe.cso.uiuc.edu>
Date: 11 Feb 89 15:36:00 GMT
References: <10@dbase.UUCP>
Lines: 19
Nf-ID: #R:dbase.UUCP:10:uxe.cso.uiuc.edu:225800128:000:579
Nf-From: uxe.cso.uiuc.edu!mcdonald    Feb 11 09:36:00 1989



>	#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().
And on some computers
      (FALSE == TRUE)   returns 0, while on others
      (FALSE == TRUE)   will return 1! (Hint: There are a few, a very
few, C compilers for one's complement machines, and on some of those
0 == -0). I admit this is farfetched.