This is the answer of Exercise #9: No for-loops.

Question #21: CopyFirst

Replace the for-loop. You will need:

boost::bind


#include <vector>



///CopyFirst copies the first std::pair elements from a std::vector of std::pairs

//From http://www.richelbilderbeek.nl/CppCopyFirst.htm

template <class T, class U>

const std::vector<T> CopyFirst(const std::vector<std::pair<T,U> >& v)

{

  std::vector<T> w;

  const int size = static_cast<int>(v.size());

  for (int i=0; i!=size; ++i)

  {

    w.push_back(v[i].first);

  }

  return w;

}

Answer


#include <algorithm>

#include <vector>

#include <boost/lambda/bind.hpp>

#include <boost/lambda/lambda.hpp>



///CopyFirst copies the first std::pair elements from a std::vector of std::pairs

//From http://www.richelbilderbeek.nl/CppCopyFirst.htm

template <class T, class U>

const std::vector<T> CopyFirst(const std::vector<std::pair<T,U> >& v)

{

  std::vector<T> w;

  std::transform(

    v.begin(),

    v.end(),

    std::back_inserter(w),

    boost::lambda::bind(&std::pair<T,U>::first, boost::lambda::_1)

    );

  return w;

}

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(C++) Answer of exercise #9: No for-loops #21

Question #21: CopyFirst

Answer