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

6 Mar 2008

      Hello
...
I couldn't figure out how to use a logical negation in the 
following situation.
struct IsConditionValid : public unary_function {
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 
...

remove_copy_if(
	events.begin(), events.end(),
	back_inserter(result),
	!boost::bind(IsConditionValid(), _1)
);

Regards

Jean-Pierre Bergamin