FetchBlockHeaderReqLens

alias to set

Composes two lenses, this enables nesting.

If our field of type A has a sub-field of type B, then given a lens for it (other: Lens[A, B]) we can create a single lens from Container to B.

Creates a sub-lens

Creates a sub-lens

get knows how to extract some field of type A from a container

Represent an update operator (like x.y += 1 )

Represents an assignment operator.

Given a value of type A, sets knows how to transform a container such that a is assigned to the field.

We must have get(set(a)(c)) == a

Optional assignment.

Given a Some[A], assign the Some's value to the field. Given None, the container is unchanged.

Given two lenses with the same origin, returns a new lens that can mutate both values represented by both lenses through a tuple.