TRUE and FALSE

[Rahul Dhesi]

In <1990Aug29.153917.28110 at warwick.ac.uk> asrap at 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 at oliveb.ATC.olivetti.com>
UUCP:  oliveb!cirrusl!dhesi