5.8

/* comment
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define CUBE_LOWER 1e-6
#define CUBE_UPPER 1e+6
#define CUBE_ITERATIONS 25

int near_equal(double a, double b);
double cube_root(double v);

int
main(int argc, char *argv[]) {
	double v;
	printf("Enter v: ");
	scanf("%lf", &v);
	cube_root(v);
	return 0;
}

int
near_equal(double a, double b){
	if (a==b && b==0.00000){
		return 1;
	}else if((1.0001*a>=b && .9999*a<=b)|| (1.0001*b>=a && .9999*b<=a)){
		return 1;
	}else{
		return 0;
	}
}

double
cube_root(double v){
	double next=1.0;
	if (fabs(v)<CUBE_LOWER || fabs(v)>CUBE_UPPER)  {
		printf("Warning: cube root may be inaccurate\n");
	}
	while (!near_equal(next*next*next,v)){
		next = (2*next + v/(next*next))/3;
		printf("%lf\n", next);
	}
	return next;
}