x power y?

I made the following function to calculate x power y..
I'd like to upgrade it to make it possible to calculate even if y is decimal.. ex 2^3.456

is that possible?
Im not asking for full code just ideas..

Code:

---

double power(double pow, double from)        // x power y
{
      double temp =  from;
      if(pow > 0)
      {
          --pow;                                // x power 1 means x 1 time not 2 times !
          for(int i = 0; i < pow; i++)          temp *= from;        // temp = from x times
      }
      else if(pow < 0)         
      {
          --pow;                                        //  10/10 = 1 so must add 1..
          for(int i = 0; i > pow; --i)          temp /= from;        // temp = from divided x times
      }
      else if (pow == 0) temp = 1;                        // x power 0 == 1
      return temp;
}

---

If you include math.h, you can use pow()

double pow(double x, double y);
float pow(float x, float y); [C++ only]
long double pow(long double x, long double y); [C++ only]
double pow(double x, int y); [C++ only]
float pow(float x, int y); [C++ only]
long double pow(long double x, int y); [C++ only]

The function returns x raised to the power y, x^y.

that is an option but id like to try to make it myself..

I finally decided to use math.h since I really dunno how to calculate it..
ex: 2^2.5=5.656854249

:confused:

One way to calculate it yourseld is to use logarithms:

ln( x^y ) = y * ln(x)

x^y = e^( y*ln(x) )

In C++:

Code:

---

double myPower(double x, double y)
{
  return exp( y * log(x) );
}

---

I couldn't figure it out either. I was thinking that maybe logs were the answer... But, I don't know how to do logs "by hand" either. (Trial & error and interpolation?) So, you still have to use math.h. I know they (the Greeks?) were doing logs long before calculators and computers... Somebody had to figure out where to put the marks on the slide rule!

Yeah, I think they used a trig table and interpolation. Back then, they did out long calculations by hand. They didn't have tv and had to find something to do I guess.