I am trying to brush up on C after about 12+ years, which was two semesters at college. This program works, but I am poor on recursion and wonder if there are some tips that could be offered. Using Borland Turbo C++ 4.5 (yes, old) on win XP pro and win7 pro 32 bit machines.

Code:

/* 9.8 Mod listing 6.18 to all cases of integer powers using recursion */
#include <stdio.h>
double power(double a, int b); /* function prototype */
int main (void)
{
double x, xpow;
int n;
printf("Enter a number and the integer power to which\n");
printf("the number will be raised. Enter q to quit.\n");
while(scanf("%lf%d", &x, &n) == 2)
{
xpow = power(x,n);
printf("%.3e to the power %d is %.3e\n", x, n, xpow);
}
return 0;
}
double power(double a, int b) /* POWER function */
{
double pow = 1;
int b1;
if (b == 0) /* case of any number raised to 0 is 1 */
return 1.0;
else
if (a == 0.0) /* case of 0 to any power but 0 is 0 */
return 0.0;
else /* do non 0 pos and neg powers and numbers */
{
if (b > 0) /* normalize the power to a positive number */
b1 = b; /* since fractions are not as accurate */
else
b1 = -1 * b;
pow = a; /* calculate power doing recursive call */
pow *= power(pow, b1-1);
if (b < 0.0) /* case of negative exponents */
pow = 1.0/pow;
return pow;
}
}