How do I find an element position in std::vector?

Question

I need to find an element position in an std::vector to use it for referencing an element in another vector:

int find( const vector& whe         


        

Answer 1

std::vector has random-access iterators. You can do pointer arithmetic with them. In particular, this my_vec.begin() + my_vec.size() == my_vec.end() always holds. So you could do

const vector::const_iterator pos = std::find_if( firstVector.begin()
                                                     , firstVector.end()
                                                     , some_predicate(parameter) );
if( position != firstVector.end() ) {
    const vector::size_type idx = pos-firstVector.begin();
    doAction( secondVector[idx] );
}

As an alternative, there's always std::numeric_limits::size_type>::max() to be used as an invalid value.