The copy_if algorithm looks something like this(taken from MSVC2010):

template<class InIt, class OutIt, class Pr> inline OutIt copy_if(InIt First, InIt Last, OutIt Dest, Pr Pred) { for (; First != _Last; ++First) if (Pred(*_First)) *Dest++ = *First; return (Dest); } 

And as you can see the copy_if does not do…