university/S1/GdCP/klausur_uebung/sqrtrec.c

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

//#include "testing-0xx.h"

double sqrt_rec(double x, double p) {
  // Check for edge cases
  if (x == 0 || x < 0) {
    return 0;
  } 

  // Get the next element like the formula provided
  double next = 0.5 * (p + x/p);

  // Decide whether to go further
  if (fabs(next - p) < DBL_EPSILON) {
    return next;
  } 

  // Recusrevely try the next element in the series
  return sqrt_rec(x, next);
}

int main() {
  printf("%f\n", sqrt_rec(2, 1));
  printf("%f\n", sqrt_rec(4, 1));
  printf("%f\n", sqrt_rec(8, 1));
  printf("%f\n", sqrt_rec(9, 1));
}