(PHP 4 >= 4.1.0, PHP 5, PHP 7)
hypot — 计算一直角三角形的斜边长度
$x
, float $y
)
hypot() 函数将会跟据直角三角形的两直解边长度
x 和 y 计算其斜边的长度。或者是从标点
(x, y) 到原点的距离。该函数的算法等同于
sqrt(x*x + y*y)。
x第一条边的长度
y第二条边的长度
计算斜边的长度
If you need a higher-dimensional diagonal length (norm), you can exploit the fact that sqrt(x*x+y*y+z*z) == sqrt(x*x+sqrt(y*y+z*z)). In other words hypot(x, y, z)==hypot(x, hypot(y, z)).
To be generic about it....
<?php
function norm(...$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.
?>