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);
}
?>
hypot
(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)
hypot — Calculate the length of the hypotenuse of a right-angle triangle
Description
hypot() returns the length of the hypotenuse of a
right-angle triangle with sides of length x and
y, or the distance of the point
(x, y) from the origin.
This is equivalent to sqrt($x*$x + $y*$y).
Parameters
-
x -
Length of first side
-
y -
Length of second side
Return Values
Calculated length of the hypotenuse
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User Contributed Notes 2 notes
Hayley Watson ¶
7 years ago
robinv at ecosse dot net ¶
20 years ago
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.
?>
