hypot.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <math.h>
/*
 * sqrt(a^2 + b^2)
 *	(but carefully)
 */

double
hypot(double a, double b)
{
	double t;

	if(a < 0)
		a = -a;
	if(b < 0)
		b = -b;
	if(a > b) {
		t = a;
		a = b;
		b = t;
	}
	if(b == 0) 
		return 0;
	a /= b;
	/*
	 * pathological overflow possible
	 * in the next line.
	 */
	return b * sqrt(1 + a*a);
}