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(C++) SumFirst

 

SumFirst is the answer of question #21 of Exercise #9: No for-loops.

 

 

 

 

 

STL STL SumFirst

 

You may contact me if you have an STL solution...

 

 

 

 

 

Boost Boost.Bind SumFirst

 

Thanks to 'ofwolfandman':

 

#include <functional>
#include <numeric>
#include <utility>
#include <vector>
#include <boost/bind.hpp>

int SumFirst(const std::vector<std::pair<int,int> >& v)
{
  return std::accumulate(
    v.begin(),
    v.end(),
    static_cast<int>(0),
    boost::bind(
      std::plus<int>(),
      _1,
      boost::bind<int>(&std::pair<int,int>::first, _2)
      )
    );
}

 

 

 

 

 

Boost Boost.Lambda SumFirst

 

Thanks to 'ofwolfandman':

 

#include <functional>
#include <numeric>
#include <utility>
#include <vector>
#include <boost/lambda/lambda.hpp>
#include <boost/lambda/bind.hpp>

int SumFirst(const std::vector<std::pair<int,int> >& v)
{
  return std::accumulate(
    v.begin(),
    v.end(),
    static_cast<int>(0),
    boost::lambda::_1
    + boost::lambda::bind(
      &std::pair<int, int>::first, boost::lambda::_2
      )
  );
}

 

 

 

 

 

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