#include <stdio.h>
#include <math.h>

double pow(int);
int computeFloat(int, int, double);
double reconstructFloat(int, int, int, int, int);
void floatMult(int, int, int, int, int, int, int, int);

int main(int argc, char** arv)
{
  printf("Number\t\tSign\tExp\tMantissa\tReconstructed\n\n");
  
  int i = 0;
  int expSize = 4;
  int mantSize = 5;

  for (i = -15; i < 16; i++)
  {
    if (i != 0)
      {
	printf("%f:\t", (double)i);
	computeFloat(expSize, mantSize, (double) i);
      }
  }
  
  floatMult(expSize, mantSize, 1, 11, 28, 0, 9, 0);
}

int computeFloat(int expSize, int mantissaSize, double number)
{
  double normaliser = (double) (1 << (expSize - 1));
  double scale;
  double exp;
  double tempNumber;
  int i;

  int reconSign;
  int reconExp;
  int reconMantissa;

  if (number < 0.0)
  {
    reconSign = 1;
    number = -1 * number;
  }
  else
  {
    reconSign = 0;
  }

  /* Cheap way to get the exponent. You wont need to do this in HW */
  exp = computeExp(number);

  /* Normalise this so is 1.something */
  
  if (exp < 0) /* we want it to round the right way...*/
    number = number /= pow((int)exp - 1);
  else
    number = number /= pow((int)exp);
    

  number = number - 1.0;
  tempNumber = number;


  /* This litte bit computes the mantissa */
  scale = 0.5;
  reconMantissa = 0;
  for (i = 0; i < mantissaSize; i++)
    {
      reconMantissa = reconMantissa << 1;
      if (number >= scale)
	{
	  reconMantissa += 1;
	  number -= scale;
	}

      scale /= 2;
    }

  /* Print out some stuff about the number we tried */

  printf("%d\t%d\t%d\t\t", reconSign, reconExp, reconMantissa);
  printf("%f\n", reconstructFloat(expSize, mantissaSize, reconSign, reconExp, reconMantissa));
}

double reconstructFloat(int expSize, int mantSize, int sign, int exp, int mant)
{
  double reconNumber;
  
  if (sign)
    reconNumber = -1.0;
  else
    reconNumber = 1.0;
  
  exp -= 1 << (expSize - 1);
  
  reconNumber *= pow(exp);
  
  reconNumber *= 1.0 + ((double)mant) /  pow(mantSize);
    
  return(reconNumber);
}

double pow(int x)
{
  double retVal = 1.0;
  int i;

  if (x > 0)
    {
      for (i = 0; i < x; i++)
	retVal *= 2.0;
    }
  else
    {
      for (i = 0; i > x; i--)
	retVal /= 2.0;
    }

  return(retVal);
}


/* Computes the exponent of a POSITIVE double */
int computeExp(double num)
{
  int counter;

  if (num > 1.0)
    {
      for (counter = 0; num > 2.0; count++)
	num /= 2.0;
    }

  else
    {
      for (counter = 0; num < 1.0; count--)
	num *= 2.0;
    }
}