I have written a program in boost which simply calculates the exponent in an interval, but for some interval inputs it is giving the wrong output such as for [1,3] or [-1,3]...but for some values it is giving correct o/p such as [1,9]. Please help in  solving this query.

The program is appended below....
*********************************************************************************************************************************************************
#include </boost/numeric/interval.hpp>
#include <vector>
#include <algorithm>
#include <utility>
#include <iostream>
#include <iomanip>
#include <math.h>

 using namespace boost;
  using namespace numeric;
  using namespace interval_lib;

template<class T, class Policies>
std::ostream &operator<<(std::ostream &os,
                         const boost::numeric::interval<T, Policies> &x) {
  os << "[" << x.lower() << ", " << x.upper() << "]";
  return os;
}


int main()
{
 
  typedef interval<double,policies<save_state<rounded_transc_opp<double> >,checking_base<double> > > I;
  //typedef interval<double> I;
  I a(1,3.2);
  std::cout << exp(a) << std::endl;
 
}
**********************************************************************************************************************************************************

Thanks in Advance.

Regards,

PV