Function and

You can think of this like a short-circuiting logical "and" operation on a Maybe type. If maybe is just, then the result is the andMaybe. If maybe is Nothing, the result is Nothing.

This is useful when you have another Maybe value you want to provide if and only if you have a Just – that is, when you need to make sure that if you Nothing, whatever else you're handing a Maybe to also gets a Nothing.

Notice that, unlike in map or its variants, the original maybe is not involved in constructing the new Maybe.

Examples

import Maybe from 'true-myth/maybe';

const justA = Maybe.just('A');
const justB = Maybe.just('B');
const nothing: Maybe<number> = nothing();

console.log(Maybe.and(justB, justA).toString());  // Just(B)
console.log(Maybe.and(justB, nothing).toString());  // Nothing
console.log(Maybe.and(nothing, justA).toString());  // Nothing
console.log(Maybe.and(nothing, nothing).toString());  // Nothing
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