std::map::insert return value?

Question

typedef TriIndex ...
typedef std::map< TriIndex, unsigned int > VertexMap;
VertexMap vertex_map;

for ( size_t i = 0; i < face.size(); ++i ) { 
    for ( size_t j = 0; j < 3; ++j ) {
        std::pair< VertexMap::iterator, bool > rv = vertex_map.insert( std::make_pair(     face.v[j], vert_idx_counter ) );
        if ( rv.second ) {
            //do stuff
        }
    }
}

I took out a snippet from an opengl starter code. I get what it's doing except for the following line:

std::pair< VertexMap::iterator, bool > rv = vertex_map.insert( std::make_pair(     face.v[j], vert_idx_counter ) );

I get that the line declares a pair called rv with an iterator and a boolean value - . But on the right hand side, there is vertex_map.insert - but from what i know, insert is a void function. How do you get a pair from inserting a pair to vertex map?

Answer 1

vertex_map与'std :: map <TriIndex，unsigned int>'相同，因此您正在调用地图的插入函数，有关更多详细信息，请参阅文档std :: map :: insert