Run Time C++ Dependent Type Experiment - zip

safe_zip.cpp

#include <vector>
#include <string>
#include <iostream>
#include "optional.hpp"

using nonstd::optional;

class prove_same_size
{
public:
   static optional<prove_same_size> prove(std::vector<int> const& v1, std::vector<int> const& v2)
   {
      if (v1.size() == v2.size())
         return prove_same_size(v1,v2);
      return {};
   }

   std::vector<int> const& v1_;
   std::vector<int> const& v2_;

private:
   explicit prove_same_size(std::vector<int> const& v1, std::vector<int> const& v2) : v1_(v1), v2_(v2) {}
};


auto zip(std::vector<int> const& v1, std::vector<int> const& v2)
{
   std::vector<std::pair<int, int>> zipped;
   for (int i = 0; i < v1.size(); ++i)
      zipped.push_back({ v1[i], v2[i] });
   return zipped;
}

auto zip(prove_same_size const& vecs)
{
   std::vector<std::pair<int, int>> zipped;
   zipped.reserve(vecs.v1_.size());
   for (int i = 0; i < vecs.v1_.size(); ++i)
      zipped.push_back({ vecs.v1_[i], vecs.v2_[i] });
   return zipped;
}



int main()
{
   std::vector<int> const v1 = { 1,2,3,4 };
   std::vector<int> const v2 = { 4,3,2,1 };

   auto zipped = zip(v1, v2);

   auto y = prove_same_size::prove(v1, v2); // this is the proof

   if (y)
   {
      auto zipped = zip(y.value());
      assert(v1.size() == zipped.size());
   }
   else
      std::cout << "Input different sizes!" << std::endl;
}