Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!tymix!cirrusl!sunfire!dhesi
From: dhesi%cirrusl@oliveb.ATC.olivetti.com (Rahul Dhesi)
Newsgroups: comp.lang.c
Subject: Re: TRUE and FALSE
Message-ID: <2342@cirrusl.UUCP>
Date: 31 Aug 90 01:57:23 GMT
References: <11215@alice.UUCP> <514@demott.COM> <2316@cirrusl.UUCP> <1990Aug29.153917.28110@warwick.ac.uk>
Sender: news@cirrusl.UUCP
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In <1990Aug29.153917.28110@warwick.ac.uk> asrap@warwick.ac.uk (Sean
Legassick) explains why he might want to use enum {false, true} for
booleans in C and continues:

>I would be interested in anyone who thinks an int declaration of
>a boolean variable is clearer.

It depends.  Try this:

     typedef enum {false, true} bool;
     ...
     while ((c = getc(stdin)) != EOF) {
        bool got_digit;
	got_digit = isdigit(c);
	...
	if (got_digit == true) {
	   ...
	}
     }

Since isdigit() is not guaranteed to return 0 or 1, the value of
got_digit could be something else (e.g. 4).  Then, even when got_digit
is true by C conventions (nonzero), it isn't necessarily equal to its
enumeration value "true".

No matter what you do, you cannot in C get around this:

     Although the result of a boolean condition is always 0 or 1, all
     nonzero values are considered to be true in a boolean context.
     All mechanisms that try to represent this fact using only two
     values (e.g. TRUE and FALSE, or enum {false, true}) are likely to
     lead to bad code that looks good.
--
Rahul Dhesi <dhesi%cirrusl@oliveb.ATC.olivetti.com>
UUCP:  oliveb!cirrusl!dhesi