Idea for more delegations in <algorithm>

[Paolo Carlini]

Hi everyone, hi Chris,

today I got an idea, or better I *read* an idea: do you know N1758? 
Basically, Siek et al., explain at pag. 37 how to to do dispatching 
without tag types. Nothing very exoteric, actually, if you know 
enable_if, but this strikes me as potentially solving at the root the 
optimization problems with empty classes! Because we do *not* have 
additional parameters in the function calls!

For instance, they implement "do the right thing" for vector as:

    template<typename InputIterator>
       vector<InputIterator first, InputIterator last,
                   typename 
enable_if<(!is_integral<InputIterator>::value), void*>::type = 0);

Or, for some reason, we have troubles with this too? :(

Paolo.