C/C++ C++: Extracting Exponent Value from a Double

[madmike159]

Is there a way to look at a double value in c++ and read the exponent only and put this into another variable?
So if I had 3.14159x10^300
I could take 300, put it into an int
Then divide 3.14159x10^300 by 1x10^(the int value)

 

[DrGreg]

Here's a hint: log10(...)

 

[Mark44]

The internal representation of doubles and floats does not use powers of 10. Instead, values of these types are stored with 1 bit for the sign, another group of bits for the mantissa (which is usually called the significand) and another group of bits for the exponent on 2.

The frexp() function in math.h might be what you're looking for.
This code and the output that is shown are from http://www.cplusplus.com/reference/clibrary/cmath/frexp/.

/* frexp example */
#include <stdio.h>
#include <math.h>

int main ()
{
  double param, result;
  int n;

  param = 8.0;
  result = frexp (param , &n);
  printf ("%lf * 2^%d = %f\n", result, n, param);
  return 0;
}

Output:
0.500000 * 2^4 = 8.000000