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@@ -1 +1,104 @@ -https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html +# php-next-after + +A PHP library that provides a port of Java's `Math.nextAfter()` family of functions. + + +## Overview + +This library implements IEEE 754 floating-point manipulation functions that return the next representable floating-point value in a given direction: + +- `nextAfter($x, $y)` - Returns the adjacent float in the direction of another value +- `nextUp($x)` - Returns the next float toward positive infinity +- `nextDown($x)` - Returns the next float toward negative infinity + + +## Requirements + +- PHP 8.3 or higher +- 64-bit integers +- IEEE 754 double-precision floats (binary64) + + +## Installation + +```bash +$ composer require nsfisis/next-after +``` + + +## Exapmles + +```php +use Nsfisis\NextAfter\NextAfter; + +// Get the next representable float after 1.0. +$next = NextAfter::nextAfter(1.0, 2.0); // => 1.0000000000000002 + +// Get the next float toward positive infinity. +$up = NextAfter::nextUp(1.0); // => 1.0000000000000002 + +// Get the next float toward negative infinity. +$down = NextAfter::nextDown(1.0); // => 0.9999999999999999 +``` + + +## API Reference + +### `nextAfter(float $x, float $y): float` + +Returns the floating-point number adjacent to `$x` in the direction of `$y`. If `$x` equals `y`, returns `y`. + +#### Special Cases + +- If either argument is NaN, the result is NaN +- If both arguments equal, `$y` is returned as it is +- If `$x` is `minValue()` and `$y` is greater than `$x`, the result is positive zero +- If `$x` is `-minValue()` and `$y` is less than `$x`, the result is negative zero +- If `$x` is infinity and `$y` is not, `PHP_FLOAT_MAX` is returned +- If `$x` is negative infinity and `$y` is not, `-PHP_FLOAT_MAX` is returned +- If `$x` is `PHP_FLOAT_MAX` and `$y` is infinity, infinity is returned +- If `$x` is `-PHP_FLOAT_MAX` and `$y` is negative infinity, negative infinity is returned + +### `nextUp(float $x): float` + +Returns the floating-point value adjacent to `$x` in the direction of positive infinity. + +This is semantically equivalent to `nextAfter($x, INF)`. + +#### Special Cases + +- If `$x` is NaN, the result is NaN +- If `$x` is positive infinity, the result is positive infinity +- If `$x` is zero, the result is `minValue()` +- If `$x` is `-minValue()`, the result is negative zero +- If `$x` is `PHP_FLOAT_MAX`, infinity is returned + +### `nextDown(float $x): float` + +Returns the floating-point value adjacent to `$x` in the direction of negative infinity. + +This is semantically equivalent to `nextAfter($x, -INF)`. + +#### Special Cases + +- If `$x` is NaN, the result is NaN +- If `$x` is negative infinity, the result is negative infinity +- If `$x` is zero, the result is `-minValue()` +- If `$x` is `minValue()`, the result is positive zero +- If `$x` is `-PHP_FLOAT_MAX`, negative infinity is returned + +### `minValue(): float` + +Returns the minimum representable non-zero floating-point number. Note that this is a subnormal number and is not the same as `PHP_FLOAT_MIN`, which is the smallest *normal* number. + + +## License + +See the [LICENSE](./LICENSE) file. + + +## Credits + +This library is a PHP port of Java's `java.lang.Math.nextAfter()`, `nextUp()`, and `nextDown()` methods. + +Reference: [Java Math Documentation](https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html) |