Building a vector from components contained in another vector type

Question

I have a code that looks something like this:

struct First
{
    int f1;
    int f2;
};

struct Second
{
    First s1;
    int s2;
};

std::vector < Second > secondVec;

Second sec;
sec.s1 = First(); 

secondVec.push_back(sec);
secondVec.push_back(sec);

std::vector < First > firstVec;
firstVec.reserve(secondVec.size());

for (std::vector < Second >::iterator secIter = secondVec.begin(); 
         secIter != = secondVec.end();
         ++secIter)
{
    firstVec.push_back(secIter->s1);
}

I'd like to replace this ugly for loop with a simple stl function that could perhaps perform the equivalent process. I was thinking that maybe std::transform could help me here, but I'm unsure as to how this could be written.

I'd also be interested if boost has anything to offer here.

Answer 1

If you have TR1 or Boost available, you could try this:

std::transform(secondVec.begin(),
               secondVec.end(),
               std::back_inserter(firstVec),
               std::tr1::bind(&Second::s1, _1));