RE: [boost] Re: safe_bool alternative?

From: Sam Partington (sam.partington_at_[hidden])
Date: 2003-11-25 12:31:43

Douglas Paul Gregor <mailto:gregod_at_[hidden]> wrote:
> On Tue, 25 Nov 2003, Sam Partington wrote:
>> I've been playing with the idea of selecting from either
>> implementation as suitable :
> [snip]
>> template<class T, class B = ::boost::detail::empty_base> 	class
>> 		the_bool_testable : public select_bool_impl<safe_bool<T, B>,
>> 						bool_testable<T, B>,
>> 						boost::is_convertible<T,
>> int>::value
>> 						>
> 
> This can't work, because it's impossible for the type T to be
> defined, so is_convertible<T, int> won't give a meaningful result.

I rather suspected as much.  To be honest I was rather surprised it
compiled.  Is there no way we can work out whether the user provides a user
defined integral conversion operator at that stage?  I guess not.

In that case could we make the implementation decision as a policy.  It
could default to safe-bool, if that is peoples preference.

Perhaps this is making things too complicated, but I want to make sure we've
explored all possibilities before a decision is made.

Sam

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