hypot()

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

计算一直角三角形的斜边长度

说明

hypot(float $x,float $y):float

hypot()函数将会跟据直角三角形的两直解边长度$x和$y计算其斜边的长度。或者是从标点($x,$y)到原点的距离。该函数的算法等同于sqrt(x*x + y*y)。

参数

$x

第一条边的长度

$y

第二条边的长度

返回值

计算斜边的长度

If you need a higher-dimensional diagonal length (norm), you can exploit the fact that sqrt(x*x+y*y+z*z) == sqrt(x*x+sqrt(y*y+z*z)). In other words hypot(x, y, z)==hypot(x, hypot(y, z)).
To be generic about it....
<?php
function norm(...$args)
{
  return array_reduce($args, 'hypot', 0);
}
?>

A simpler approach would be to allow an arbitrary number of parameters. That would allow for whatever number of dimensions you want *and* it would be backwards compatible with the current implementation.
<?php
function hypo() 
{
  $sum = 0;
  foreach (func_get_args() as $dimension) {
    if (!is_numeric($dimension)) return -1;
    $sum += pow($dimension, 2);
  }
  return sqrt($sum);
}
print hypo();     // vector in 0 dimensions, magnitude = 0.
print hypo(1);     // vector in 1 dimension, magnitude = 1.
print hypo(3, 4);    // vector in 2 dimensions, magnitude = 5.
print hypo(2, 3, 6);   // vector in 3 dimensions, magnitude = 7.
?>