using STL to find all elements in a vector

Question

I have a collection of elements that I need to operate over, calling member functions on the collection:

std::vector v;
... // vector is popula         


        

Answer 1

Boost Lambda makes this easy.

#include 
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std::for_each( v.begin(), v.end(), 
               if_( MyPred() )[ std::mem_fun(&MyType::myfunc) ] 
             );

You could even do away with defining MyPred(), if it is simple. This is where lambda really shines. E.g., if MyPred meant "is divisible by 2":

std::for_each( v.begin(), v.end(), 
               if_( _1 % 2 == 0 )[ std::mem_fun( &MyType::myfunc ) ]
             );

---

Update: Doing this with the C++0x lambda syntax is also very nice (continuing with the predicate as modulo 2):

std::for_each( v.begin(), v.end(),
               [](MyType& mt ) mutable
               {
                 if( mt % 2 == 0)
                 { 
                   mt.myfunc(); 
                 }
               } );

At first glance this looks like a step backwards from boost::lambda syntax, however, it is better because more complex functor logic is trivial to implement with c++0x syntax... where anything very complicated in boost::lambda gets tricky quickly. Microsoft Visual Studio 2010 beta 2 currently implements this functionality.