Comparing quantities

Comparison methods operate on native values, so two quantities expressed in different units compare correctly. Unlike add() and subtract(), comparison methods require the operands to be the same quantity type and throw InvalidArgumentException otherwise.

Ordering methods

use Renfordt\UnitLib\Length;

$a = new Length(1, 'km');
$b = new Length(500, 'm');
$c = new Length(1000, 'm');

$a->greaterThan($b);            // true
$a->lessThan($b);               // false
$a->greaterThanOrEqualTo($c);   // true
$a->lessThanOrEqualTo($c);      // true

compareTo

compareTo() returns -1, 0, or 1, which makes it directly usable as a sort comparator:

$lengths = [
    new Length(5, 'm'),
    new Length(200, 'cm'),
    new Length(3000, 'mm'),
];

usort($lengths, fn($a, $b) => $a->compareTo($b));
// Ordered: 2 m, 3 m, 5 m

Equality

equals() compares native values within a tolerance to account for floating-point rounding. The default tolerance is 1e-10; pass a different epsilon as the second argument:

$a = new Length(1, 'km');

$a->equals(new Length(1000, 'm'));        // true
$a->equals(new Length(1000, 'm'), 0.001); // true with a wider tolerance

Type checking

All comparison methods reject operands of a different quantity type:

use Renfordt\UnitLib\{Length, Mass};

(new Length(1, 'm'))->greaterThan(new Mass(1, 'kg'));
// InvalidArgumentException: Cannot compare ...Length with ...Mass