On Sat, 22 May 2004 13:11:39 -0400, David Abrahams <dave@boost-consulting.com> wrote:
Gennaro Prota <gennaro_prota@yahoo.com> writes:
On Sun, 16 May 2004 10:40:52 -0400, David Abrahams <dave@boost-consulting.com> wrote:
So, should I just remove it?
Well, not because it isn't implementable.
Sorry, I can't parse that. Should I remove it or not? Is it implementable?
It's my English to be quite unparseable ;) Yes, I showed a possible implementation in the last post: // Macro for when you need a constant expression. // Note that 'expr' appears three times but is // evaluated (at most) once. #define BOOST_IMPLICIT_CAST(dest_type, expr) \ (static_cast< dest_type >( \ sizeof(boost::implicit_cast< dest_type >(expr)) ? \ (expr) : (expr) \ ) \ ) As you see, it's a simple static_cast < type-id > ( expression ) plus the implicit_cast<> test inside a sizeof. The difference with the other version (which had the typename problem you point out) is that sizeof is used inside the *expression* instead of the type-id; thus no template class is used as a helper and no typename keyword must be "hard-coded" inside the macro definition. So: if the only reason why you wanted to remove it was the typename problem then the macro can remain :) OTOH, I understand you might want to remove it anyway, as "implicit casts" in constant expressions aren't the most frequent thing C++ programmers do. It's up to you, I think. I wrote it mainly for fun.
Maybe your code below answers those questions...
Yes, there was a new implementation and a few examples usages.
[...]
I like it. Maybe it's time to document this stuff, too ? ;-)
Ok :) Let me know if you want to leave it or not. Genny.