README

A set of numbers between two endpoints.

use Jstewmc\Interval;

// create an interval between 2 (exclusive) and 4 (inclusive)
$interval = new Interval('(2, 4]');

// compare values
$interval->compare(1);  // returns -1
$interval->compare(2);  // returns -1
$interval->compare(3);  // returns 0
$interval->compare(4);  // returns 0
$interval->compare(5);  // returns 1

// echo the interval
echo $interval;  // returns "(2, 4]"

Syntax

This library supports standard US interval syntax requiring (in order):

• an open-bracket ([) or open-parentheses (();
• a number, positive infinity (INF), or negative infinity (-INF);
• a comma-space (, );
• a number, positive infinity (INF), or negative infinity (-INF); and,
• a close-bracket (]) or close-parentheses ()).

Positive or negative floats, integers, and infinity are accepted.

For example:

• (2, 4] represents 2 < x <= 4
• (-10.5, 10.5) represents -10.5 < x < 10.5
• [0, INF) represents 0 <= x < ∞
• (-INF, INF) represents -∞ < x < ∞

Keep in mind, this library does not support reverse-bracket syntax (e.g., ]2, 4]) or semi-colon separated syntax (e.g., [2; 4]).

Usage

You can instantiate an interval from a string or create it manually using the set methods:

use Jstewmc\Interval;

$a = new Interval('(2, 4]');

$b = (new Interval())
    ->setLowerExclusive()
    ->setLower(2)
    ->setUpper(4)
    ->setUpperInclusive();

$a == $b;  // returns true

Keep in mind, when instantiating an interval from a string, an InvalidArgumentException will be thrown if the interval's syntax is invalid:

use Jstewmc\Interval;

new Interval('[0; 0]');      // throws exception (semicolon syntax not supported)
new Interval(']0, 2]');      // throws exception (reverse brackets not supported)
new Interval('[foo, bar]');  // throws exception (use numbers or INF)
new Interval('[0, 0)');      // throws exception (same endpoint, different boundary)
new Interval('[1, -1]');     // throws exception (upper- is less than lower-bound)

Infinity is supported as the string 'INF' or the INF predefined constant:

use Jstewmc\Interval;

$a = new Interval('(-INF, 0]');

$b = (new Interval())
    ->setLowerExclusive()
    ->setLower(-INF)
    ->setUpper(0)
    ->setUpperInclusive(true);

$a == $b;  // returns true

You can compare a value to the interval using the compare() method. The compare() method will return -1, 0, or 1 if the value is below, inside, or above the interval, respectively:

use Jstewmc\Interval;

$interval = new Interval('(2, 4]');

$interval->compare(1);  // returns -1
$interval->compare(2);  // returns -1
$interval->compare(3);  // returns 0
$interval->compare(4);  // returns 0
$interval->compare(5);  // returns 1

You can get any of the interval's settings with the get methods:

use Jstewmc\Interval;

$interval = new Interval('(2, 4]');

$interval->getIsLowerInclusive();  // returns false
$interval->getLower();             // returns 2
$interval->getUpper();             // returns 4
$interval->getIsUpperInclusive();  // returns true

There are a few convenience methods to make getting and setting the boundaries eaiser:

use Jstewmc\Interval;

$interval = new Interval('(2, 4]');

$interval->isLowerInclusive();  // returns false
$interval->isLowerExclusive();  // returns true
$interval->isUpperInclusive();  // returns true
$interval->isUpperExclusive();  // returns false

echo $interval->setLowerInclusive();  // prints "[2, 4]"
echo $interval->setLowerExclusive();  // prints "(2, 4]"
echo $interval->setUpperInclusive();  // prints "(2, 4]"
echo $interval->setUpperExclusive();  // prints "(2, 4)"

That's about it!

License

MIT

Author

Jack Clayton

Version

1.0.0, August 13, 2016

• Major release
• Update composer.json

0.2.0, August 7, 2016

• Add support for infinity (e.g., '(-INF, 0]').
• Update error messages to be a little more informative.
• Update README examples.

0.1.0, August 6, 2016

• Initial release