Consider the following:
#include <iostream>
//#include <math.h>
#include <cmath>
using namespace std;
int main(int argc, char **argv)
{
double ldexp_signif = 0.545528;
double ldexp_expo = 12;
double ldexp_output = 0;
double frexp_input = 2234.484565523;
double frexp_signif = 0;
int frexp_expo = 0;
int n;
// create float from sig and expo
ldexp_output = ldexp (ldexp_signif , ldexp_expo);
printf ("The significand INPUT is %f\n",ldexp_signif);
printf ("The exponent INPUT is %f\n",ldexp_expo);
printf ("The float OUTPUT is %f\n\n",ldexp_output);
// get sig and expo from float
frexp_signif = frexp (frexp_input , &frexp_expo);
printf ("The float INPUT is %f\n",frexp_input);
printf ("the exponent OUTPUT is %i\n",frexp_expo);
printf ("The significand OUTPUT is %f\n",frexp_signif);
// ==================================
cout << endl << "=======================================" << endl << "Program completed and terminated successfully." << endl << "Press enter to exit";
cin.ignore();
return 0;
}
The output is:
The significand INPUT is 0.545528
The exponent INPUT is 12.000000
The float OUTPUT is 2234.482688
The float INPUT is 2234.484566
the exponent OUTPUT is 12
The significand OUTPUT is 0.545528
=======================================
Program completed and terminated successfully.
Press enter to exit
What I would like to know is why ldexp gives a float output different from the float input of frexp when ldexp is given the same significand and exponent generated by frexp? I found this article but that article didn't answer my question. I saw this also, it states that floating point calculations are not exact. The output to console is only for demonstration purposes, the significand and exponent are to be read from a game data file that was written using Single-precision floating-point format then used to display that data, it is not going to be used for anything potentially life-threating like medical or military applications, should I just take it for what it is or look for a more accurate solution?
