gmp_int

#include <boost/multiprecision/gmp.hpp>

namespace boost{ namespace multiprecision{

class gmp_int;

typedef number<gmp_int >         mpz_int;

}} // namespaces

The gmp_int back-end is used via the typedef boost::multiprecision::mpz_int. It acts as a thin wrapper around the GMP mpz_t to provide an integer type that is a drop-in replacement for the native C++ integer types, but with unlimited precision.

As well as the usual conversions from arithmetic and string types, type mpz_int is copy constructible and assignable from:

The GMP native types: mpf_t, mpz_t, mpq_t.
Instances of number<T> that are wrappers around those types: number<gmp_float<N> >, number<gmp_rational>.

It's also possible to access the underlying mpz_t via the data() member function of gmp_int.

Things you should know when using this type:

No changes are made to the GMP library's global settings - so you can safely mix this type with existing code that uses GMP.
Default constructed gmp_ints have the value zero (this is GMP's default behavior).
Formatted IO for this type does not support octal or hexadecimal notation for negative values, as a result performing formatted output on this type when the argument is negative and either of the flags std::ios_base::oct or std::ios_base::hex are set, will result in a std::runtime_error will be thrown.
Conversion from a string results in a std::runtime_error being thrown if the string can not be interpreted as a valid integer.
Division by zero results in a std::overflow_error being thrown.
Although this type is a wrapper around GMP it will work equally well with MPIR. Indeed use of MPIR is recommended on Win32.
This backend supports rvalue-references and is move-aware, making instantiations of number on this backend move aware.

Example:

#include <boost/multiprecision/gmp.hpp>
#include <iostream>

int main()
{
   using namespace boost::multiprecision;

   mpz_int v = 1;

   // Do some arithmetic:
   for(unsigned i = 1; i <= 1000; ++i)
      v *= i;

   std::cout << v << std::endl; // prints 1000!

   // Access the underlying representation:
   mpz_t z;
   mpz_init(z);
   mpz_set(z, v.backend().data());
   mpz_clear(z);
   return 0;
}