Using Result

Sometimes we want to give more information about the failure of a function than just returning None. The Result type is used to do this. It is similar to Option in that it can wrap a value, but it can also wrap an error. Result is generic over T, the type of the value, and E, the type of the error.

There are two variants of Result<T, E>:

• Ok(value), which indicates success and wraps the value of type T
• Err(why), which indicates failure and wraps a why of type E, which should explain the cause of the failure

import { Result, Ok, Err } from 'iron-oxide';

// Number.parseInt returns NaN, which we would need to check for later
// let's fix that

function parseInt(
    maybeInt: string,
    radix?: number
): Result<number, string> {
    const result = parseInt(maybeInt, radix);

    if (isNaN(result)) {
        return Err(
            `Attempted to parse ${maybeInt} as an integer`
        );
    }

    return Ok(result);
}