text: #include "include/stdinc.h"
  #include <vector>
  #include <algorithm>
  
  class data_compare : public std::binary_function<int, int, bool> {
  
     const vector<real> &data;
  
  public:
  
    data_compare(const vector<real> &d) : data(d) {};
    ~data_compare() {};
    
    bool operator() (int a, int b) const {
      return data[a] < data[b];
    };
    
  };
  
  vector<int> sort_index (vector<real>);
  
  