Re: [boost] [bind][tr1] patch for more compliant placeholders

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-04-27 20:32:26

Eric Niebler wrote:

> I'll have to take your word for it -- I'm not familiar enough with the
> TR1 bind to appreciate the difficulty of respecting
> is_bind_expression. It seems to me that is_bind_expression can be
> trivially implemented, given appropriately defined placeholders.

Implementing is_bind_expression is trivial and done. Making bind respect it 
is harder. The TR1 spec says that in

bind( f, _1 + _2 );

bind needs to look at is_bind_expression<typeof(_1+_2)>::value to determine 
whether it's a subexpression. This part is not present in boost::bind, it 
just recognizes its own bind(...) expressions without asking 
is_bind_expression.

> Result_of support for older compilers ... I suppose that requires
> partial template specialization, right? Do we still support compilers
> that don't do PTS?

Well, there are various degrees of doing PTS. Borland does PTS in principle, 
but seems to choke on pretty much every change I make. Pointers to members 
also stress even the modern compilers - we just found a pm-related bug in 
VC8. In general after a commit to boost::bind I plan on two platforms 
breaking right away, one at a later point. :-)