map

In std/collections.

elementwise fn map<F<_> : Iterable<_>, T, R>(self: F<T>, by: T -> R) : F<R>
elementwise fn map<T, R>(self: Option<T>, by: T -> R) : Option<R>
elementwise fn map<T, R, E>(self: Result<T, E>, by: T -> R) : Result<R, E>

Each element through by, in a collection of the input's constructor: [1, 2, 3] | map(x => x * 10) is [10, 20, 30]. A Set maps to its image, which may hold fewer elements than the input. Over an Option, by applies to a present value and none stays none; over a Result, by applies to the success value and a failure is unchanged.