Essential C++

count_if()

Returns a count of the number of times the operator evaluated as true.

#include <algorithm> 
class Even { 
public: 
   bool operator()( int val ){ return !( val%2 ); } 
}; 

ires = count_if( ia, ia+8, bind2nd(less<int>(),10) ); 
lres = count_if( ilist.begin(), ilist_end(), Even() );