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

Question

Replace the for-loop. You will need:

std::greater.htm
A conditional std::accumulate


int SumPositives(const std::vector<int>& v)

{

  const size_t sz = v.size();

  int sum = 0;

  for (size_t i=0; i!=sz; ++i)

  {

    if (v[i]>0) sum+=v[i];

  }

  return sum;

}

Answer


template<typename InputIterator, typename ElementType, typename Predicate>

const ElementType accumulate_if(

  InputIterator first,

  const InputIterator last,

  ElementType init,

  const Predicate predicate)

{

  for (; first != last; ++first)

    if (predicate(*first)) init += *first;

  return init;

}



#include <vector>

#include <functional>



int SumPositives(const std::vector<int>& v)

{

  return ::accumulate_if(v.begin(),v.end(),0,std::bind2nd(std::greater<int>(),0));

}

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(C++) Answer of exercise #9: No for-loops #18

Question

Answer