README

This library is a PHP-based implementation of the Result monad that exists in many popular programming languages, including Haskell, Elm, Kotlin, and Rust.

Installation

To install this library using Composer, run the following command: composer require sylvrs/libresult

Usage

The usage of the library follows similar standards to that of monads in other languages.

Creating a result

The basic creation of a result is as follows:

/**
 * @return Result<string, string>
 */
function create_result(): Result {
    return mt_rand(0, 1) > 0 ? new Ok("success!") : new Err("error!");
}
$result = create_result();

Value Extraction

From there, there are several ways to get the values from the result:

// Using PHP's match expression
$value = match (true) {
    $result instanceof Ok => $result->getValue(),
    $result instanceof Err => $result->getError(),
    // This will never occur, but is required for PHPStan to be happy in most levels
    default => assert(true)
};

// Using `Result->get()`
// Note: This will return null if the result is an error
$value = $result->get();

// Using `Result->unwrap()`
// Note: This will throw an exception if the result is an error
$value = $result->unwrap();

Useful Methods

Furthermore, there are other methods that may prove useful for working with results:

// Using `Result->asArray()`
// If the result is Ok, the array shape is [TValue, null]. Otherwise, the array shape is [null, TError]
[$value, $error] = $result->asArray();

// Using `Result->getOr()`
$value = $result->getOr("default value");

Error Handling

For cases where you know that the result is an error, you can use Result->unwrapError():

// Note: If the result is *not* an error, this will throw an exception
$error = $result->unwrapError();

Issues / Feature Requests

Any issues or requests should be reported here.