[libstdc++ PATH] tr1::bind support

[Benjamin Kosnik]

> What can we do? For one, we can scale back to 10 parameters across the 
> board. It's the minimum requirement, and although I'd like more 
> parameters it just takes too long to compile. But, we're still 3 times 
> slower than the Boost equivalents. We can try to reduce the header 
> dependencies a bit (for instance, <tr1/functional> ends up including 
> <string>, which includes <algorithm>, etc.) and factor out the core 
> parts of <tr1/functional> that <tr1/tuple> needs, so that it doesn't 
> incur all of that overhead. The long-term solution is probably 
> something like variadic templates, but that's a big undertaking for a 
> potentially esoteric feature that still hasn't been completely defined 
> :)

Thanks for the analysis. I think having the machinery to do more than 10
parameters, but only actually doing 10 parameters by default is fine.
For string, you may want to try using <bits/stringfwd.h> if you can get
away with it. 

I don't want to belabor this point (but perhaps have already done so),
but I think experimenting with designs such as tuple et. al that
implicitly require variadic templates really necessitate some kind of
experimental compiler support.

I am leery of the trickery and complexity involved in the current
implementations of these features, although I consider the implementors
themselves quite capable. :)

Anyway. I've added c++/20599 as a feature request for this.

I'm assuming 200409 (Pre Redmond) N1704 is the best reference? 

best,
benjamin