怎样求一个数的n次方

#include
double pow (double num,int n)
{
     int b;
     double a=1;
     for(b=0;b      {
          a=a*num; 
     }
          return a;
}
int main ()
{
     double num;
     int n;
     scanf("%lf%d",&num,&n);
      printf("%lf\n",pow(num,n));
      return 0;
}