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.
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()); // NothingType Parameters
T
T
The type of the initial wrapped value.
U
U
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.
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()); // NothingType Parameters
T
T
The type of the initial wrapped value.
U
U
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>
Parameters
maybe
Maybe<T>
Returns
Maybe<U>