True Myth / maybe / and

Function: and()

Call Signature

and<T, U>(andMaybe, maybe): Maybe<U>

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.

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

Type Parameters

T

T extends object

The type of the initial wrapped value.

U

U extends object

The type of the wrapped value of the returned Maybe.

Parameters

andMaybe

Maybe<U>

The Maybe instance to return if maybe is Just

maybe

Maybe<T>

The Maybe instance to check.

Returns

Maybe<U>

Nothing if the original maybe is Nothing, or andMaybe if the original maybe is Just.

Call Signature

and<T, U>(andMaybe): (maybe) => Maybe<U>

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.

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

Type Parameters

T

T extends object

The type of the initial wrapped value.

U

U extends object

The type of the wrapped value of the returned Maybe.

Parameters

andMaybe

Maybe<U>

The Maybe instance to return if maybe is Just

Returns

Nothing if the original maybe is Nothing, or andMaybe if the original maybe is Just.

(maybe) => Maybe<U>