需要帮助如何将C ++自动值传递给函数

Question

Here is my sample code shrunk down from the original and this compiles on my Mac:

#include <cmath>
#include <iostream>
#include <random>
#include <string>
#include <vector>
#include <Array>

class ranker {};

namespace detail {
  template <class T>
  struct unique_if
  {
    using single_object = std::unique_ptr<T>;
  };

  template <class T>
  struct unique_if<T[]>
  {
    using unknown_bound = std::unique_ptr<T[]>;
  };
}

/**
 * Constructs a unique ptr in place.
 * @param args The parameters to the constructor
 * @return a unique_ptr<T>
 */
template <class T, class... Args>
typename detail::unique_if<T>::single_object make_unique(Args&&... args)
{
  return std::unique_ptr<T>{new T(std::forward<Args>(args)...)};
}

template <class T>
typename detail::unique_if<T>::unknown_bound make_unique(std::size_t size)
{
  return std::unique_ptr<T>{new typename std::remove_extent<T>::type[size]()};
}

class MPtf2ln_ranker {
  private: // Change the parameters to suit your ranking function
    double lambda_ = 0;
    double alpha_ = 0;
    double s_ = 0;
    double mu_ = 0;

  public:
    MPtf2ln_ranker(); // Default Constructor
    MPtf2ln_ranker(double lambda, double alpha, double s, double mu); // Constructor
    void set_param(double lambda, double alpha, double s, double mu) {
        lambda_ = lambda; alpha_ = alpha; s_ = s; mu_ = mu;
    }; // Sets the parameters
    // Calculates the score for one matched term
    double score_one();
};//MPtf2ln_ranker CLASS

MPtf2ln_ranker::MPtf2ln_ranker(){}//MPtf2ln_ranker()
MPtf2ln_ranker::MPtf2ln_ranker(double lambda, double alpha, double s, double mu) 
: lambda_{lambda}, alpha_{alpha}, s_{s}, mu_{mu} {
}//MPtf2ln_ranker()
double MPtf2ln_ranker::score_one() {
  return 1.1;
}//score_one()

void tune(  ) {
  std::array<double,11> lambdaValues {{ 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 }};
  std::array<double,11> alphaValues  {{ 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 }};
  std::array<double,11> sValues      {{ 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 }};
  std::array<double,10> muValues     {{ 0.0, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 }};

  auto ranker = make_unique<MPtf2ln_ranker>();
  std::size_t s, m, l, a;
  s = 0; m=0; l=0; a=0;
  ranker->set_param( lambdaValues[l], alphaValues[a], sValues[s], muValues[m]);     
}

int main(int argc, char* argv[]) {
  auto ranker = make_unique<MPtf2ln_ranker>();

  tune();
  return 0;
}

In the main() the ranker needs to be passed to the tune() function. In tune() function I want to comment out its auto ranker variable and use the one that is passed in. This would allow the tune() to handle multiple rankers and not have to duplicate my code.

Hopefully someone would be willing to tell me how to do this. Thanks

Answer 1

You can use a template

template <typename T>
void tune(unique_ptr<T>& p) { /* ... */ }

[...]
tune(ranker);