Re: [Groff] on type bool

[Bernd Warken]

On Mon, May 20, 2002 at 11:37:51PM +0200, Bernd Warken wrote:
> c) Implement `bool' as follows:
> 
> #ifdef HAS_BOOL
> #  define to_bool(x) bool((x))
> #else // not HAS_BOOL
> #  define bool int
> #  define false 0
> #  define true 1
> #  define to_bool(x) (x == 0) ? 0 : 1 
> #endif // not HAS_BOOL
> 
A much better implementation is

#ifndef HAS_BOOL
typedef int bool;
#define bool(x) ((x) == 0) ? 0 : 1
#define false 0
#define true 1
#endif // not HAS_BOOL

Then casting can be done by the C++ functional cast `bool(x)', while 
the C style cast `(bool) x' will not work.  Then `to_bool()' is not
not needed.

> Together with the requirement that all casting to `bool' must be
> performed via `to_bool()', this fulfills the ANSI C++ `bool' rules
> (1)-(4) above.
> 
> d) In order to be able to transparently use `bool', the above
> implementation must be kept in a header file that is included anyway
> in any .cc source file.  `groff-source/src/include/lib.h' seems to be
> a good choice.  Or should it go to a file of its own.
> 
> Comments welcome.
> 
> Bernd Warken
> 
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