implementing map<mpz_t, double> in c++

Question

For some reason, I need to have a map from arbitrary huge number to double and I tried to implement it with c++98 (and I have to) and Xcode but it doesn't work:

#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <set>
#include "gurobi_c++.h"
#include <sstream>
#include "boost/tuple/tuple.hpp"
#include "boost/tuple/tuple_comparison.hpp"
#include "boost/tuple/tuple_io.hpp"
#include <cmath>
#include <gmp.h>

using namespace std;
using namespace ::boost::tuples;
using namespace ::boost;

int main()
{
    map<mpz_t, double>J;
    mpz_t a,b,c,n;
    string tempstring;
    int xrange=5,yrange=5,component=5;

    mpz_set_str(n,"11", 10);
    J[n]=-1;

    return 0;
}

The error shown is: Array initializer must be an initializer list. Could someone help me with it? Thank you:)

Here's the detail error page:

Answer 1

I don't know the details of mpz_t. However, it appears to be an array.

You can get around the problem by defining a class to be used as the key in your map.

I am able to create an executable using the following code with g++ 4.8.2.

#include <map>
using namespace std;

typedef int (mpz_t)[2];

struct MyKey
{
   // Add a proper implementation of a constructor
   // with mpz_t.
   MyKey(mpz_t in) {}

   // Add a proper implementation of copy constructor.
   MyKey(MyKey const& copy) {}

   // Add a proper implementation of assignment operator.
   MyKey& operator=(MyKey const& rhs)
   {
      return *this;
   }

   bool operator<(MyKey const& rhs) const
   {
      // Add a proper implementation.
      return false;
   }

   mpz_t n;
};

int main()
{
   map<MyKey, double> J;
   mpz_t n;
   J[n] = 1.0;
   return 0;
}