Remove algo duplication

[Christopher Jefferson]

I have not looked carefully at predefined_ops.h, but I can show you
some of the previous code which I know has caused problems for this
kind of simplification. I attach it below.

I agree with Marc, I think templated member functions are the way to
go. For example, I would use objects like this:

struct __less {
template<typename T, typename U>
bool operator()(T& t, U& u) { return t < u; }
};

Note the missing 'const' on T& and U& is intentional.

I attach a list of some of the weirder things I remember seeing break,
and some outline of comparitors I think might be best.

Note I have NOT tested all the cases of these comparitors, just a
suggestion as a direction we could go in.

Francois:I assume it is these kinds of problems which made we want to
change all the predicates to take iterators directly, and do the
de-referencing in-predicate. However, that does radically change
almost every algorithm. Do you have any examples of where my suggested
__less above does not work, and your redirection does? While I'm not
100% opposed to such a big change, I would want it to have excellent
justification!

Chris


On 9 September 2013 20:59, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> Hi,
>
> as far as I'm concerned, the sheer size of predefined_ops.h is the most important issue. I still can't convince myself on an intuitive level that for forwarding so much code is necessary.
>
> That said, since the real difficulty of the task boils down to proper fowarding, it seems "obvious" to me that a complete patch should come with corresponding tests, minimally exercizing the algorithms for a typical proxy iterator type, maybe even the available vector<bool>::iterator, or a specific new test type (more "nasty" than vector<bool>::iterator? In the past Howard often discussed some, in various contexts). I realize it would be a lot of work and in any case I can't promise that I would immediately approve the patch (for the reason above)
>
> Paolo
>
>
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