[arrow-optics] Is there a `Setter<S, T>` met...

# arrow

[Bob Glamm]

[arrow-optics] Is there a Setter<S, T> method that takes a T and produces an (S) -> S ? E.g. if I have:

@optics data class Foo(x: Int, y: Double)

val fooStart: Foo = Foo(1, 2.0)

// Foo.x is Lens<Foo, Int>; Foo.y is Lens<Foo, Double>
// `.set` is not the correct method here; the idea is that this just closes over the value to set in the structure
// and the structure to be modified will be supplied later
val setter1: (Foo) -> Foo = Foo.x.set(3)
val setter2: (Foo) -> Foo = Foo.y.set(4.0)

(setter1 compose setter2)(fooStart) == Foo(3, 4.0)

The idea being that all of the sets/updates would be created and then applied in bulk over the original structure.

[simon.vergauwen]

There is the function lift, that does this. https://arrow-kt.io/docs/apidocs/arrow-optics/arrow.optics/-p-setter/lift.html

val setter1 : (Foo) -> Foo = Foo.x.lift { 3 }
val setter2: (Foo) -> Foo = Foo.y.lift { 4.0 }

(setter1 compose setter2)(fooStart) == Foo(3, 4.0)

[Bob Glamm]

That's exactly what I was looking for. Thanks, Simon 🙂