Question

I have a map like this

map<string, pair< pair<int, int>, string> >

what is the easiest way to get only the two strings and save into another map like this

map<string, string>

?
I mean is there another way other than something like this??

    map<string, pair< pair<int, int>, string> >  info;
    map<string, pair< pair<int, int>, string> >::iterator i;
    map<string, string> something;


    for(i=info.begin(); i!=info.end(); ++i)
        something[*i).first] = ((*i).second).second;

Answer 1

First, I’d define a proper type:

struct Mapped
{
    int someSignificantName;
    int anotherName;
    std::string yetAnother;
};

There are almost no cases where std::pair is an acceptable solution
(except for quick hacks and tests). Given that, you define a mapping
functional object:

struct Remap
    : std::unary_operator<std::pair<std::string, Mapped>,
                          std::pair<std::string, std::string> >
{
    std::pair<std::string, std::string> operator()(
            std::pair<std::string, Mapped> const& in ) const
    {
        return std::make_pair( in.first, in.second.yetAnother );
    }
};

, then use std::transform:

std::transform( in.begin(), in.end(),
                std::inserter( out, out.end() ),
                Remap() );