Re: [boost] Disable_if_type / is_pair

Subject: Re: [boost] Disable_if_type / is_pair
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-10-12 07:33:06

Olaf van der Spek wrote:
> On Tue, Oct 11, 2011 at 8:40 PM, Stewart, Robert
> <Robert.Stewart_at_[hidden]> wrote:
>
> >> template <class T, class U>
> >> typename T::value_type::second_type* find_ptr(T& c, U v);
> >>
> >> template <class T, class U>
> >> typename iterator_traits<typename T::iterator>::pointer
> >> find_ptr(T& c, U v);
> >>
> >> What is the recommended way to disable the second overload?
> >> I didn't find a is_pair type_trait or disable_if_type.
> >
> > pair doesn't have a nested type "iterator", so SFINAE would
> > disable the second.
>
> T would be for example map or vector.
> If it's vector, the first overload is disabled.
> But if it's map, both overloads are available and the second
> one needs to be disabled 'manually'.

Right.  I was focused on the "is_pair" part of your question.

It seems like you should be able to use the usual trait class technique to determine whether c.find(v) is valid syntax and, if so, dispatch to that implementation preferentially, falling back on std::find() otherwise.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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