Re: [Boost-users] negating a functor in a remove_copy_if

From: PJ Durai (pjdtech2000_at_[hidden])
Date: 2008-03-06 13:40:29

On 3/6/08, Jean-Pierre Bergamin <james_at_[hidden]> wrote:
> Hello
>
> > I couldn't figure out how to use a logical negation in the
> > following situation.
> >
> > struct IsConditionValid : public unary_function<Event, bool> {
> > public:
> >    bool operator() (const Event& event)const {} };
> >
> > remove_copy_if(events.begin(), events.end(),
> >                            back_inserter(result),
> >                            IsConditionValid());  <--  how to
> > negate the condition object?
> >
> > What I really need is   '! IsConditionValid()'.
> >
> > How can it be done using may be boost::bind ?
>
> If you already have a unary predicate (as your IsConditionValid functor),
> you can also use the std::not1 function to negate the predicate:
>
> remove_copy_if(
>        events.begin(), events.end(),
>        back_inserter(result),
>        not1(IsConditionValid())
> );
>
> Bind overloads the ! operator for your convenience
>
> #include <boost/bind.hpp>
> ...
>
> remove_copy_if(
>        events.begin(), events.end(),
>        back_inserter(result),
>        !boost::bind(IsConditionValid(), _1)
> );
>
>

Thanks Jean-Pierre. That did the trick.