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//
// Lens.swift
// Monocle
//
// Created by Robert Böhnke on 1/17/15.
// Copyright (c) 2015 Robert Böhnke. All rights reserved.
//
public struct Lens<A, B> {
private let get: A -> B
private let set: (A, B) -> A
public init(get: A -> B, set: (A, B) -> A) {
self.get = get
self.set = set
}
public init(get: A -> B, set: (inout A, B) -> ()) {
self.get = get
self.set = { (a, b) in
var a = a
set(&a, b)
return a
}
}
}
// MARK: - Basics
public func get<A, B>(lens: Lens<A, B>, _ a: A) -> B {
return lens.get(a)
}
public func get<A, B>(lens: Lens<A, B>) -> (A) -> B {
return {(a: A) -> B in
return lens.get(a)
}
}
public func get<A, B>(lens: Lens<A, B>, _ a: A?) -> B? {
return a.map(lens.get)
}
public func get<A, B>(lens: Lens<A, B>) -> (A?) -> B? {
return {(a: A?) -> B? in
return a.map(lens.get)
}
}
public func set<A, B>(lens: Lens<A, B>, _ a: A, _ b: B) -> A {
return lens.set(a, b)
}
public func set<A, B>(lens: Lens<A, B>, _ a: A) -> (B) -> A {
return {(b: B) -> A in
return lens.set(a, b)
}
}
public func mod<A, B>(lens: Lens<A, B>, _ a: A, _ f: B -> B) -> A {
return set(lens, a, f(get(lens, a)))
}
// MARK: - Compose
public func compose<A, B, C>(left: Lens<A, B>, _ right: Lens<B, C>) -> Lens<A, C> {
let get: A -> C = { a in
return right.get(left.get(a))
}
let set: (A, C) -> A = { a, c in
return left.set(a, right.set(left.get(a), c))
}
return Lens(get: get, set: set)
}
infix operator >>> {
associativity right
precedence 170
}
public func >>> <A, B, C>(lhs: Lens<A, B>, rhs: Lens<B, C>) -> Lens<A, C> {
return compose(lhs, rhs)
}
infix operator <<< {
associativity right
precedence 170
}
public func <<< <A, B, C>(lhs: Lens<B, C>, rhs: Lens<A, B>) -> Lens<A, C> {
return compose(rhs, lhs)
}
// MARK: - Lift
public func lift<A, B>(lens: Lens<A, B>) -> Lens<[A], [B]> {
let get: [A] -> [B] = { xs in
return xs.map(lens.get)
}
let set: ([A], [B]) -> [A] = { xs, ys in
return zip(xs, ys).map(lens.set)
}
return Lens(get: get, set: set)
}
// MARK: - Split
public func split<A, B, C, D>(left: Lens<A, B>, _ right: Lens<C, D>) -> Lens<(A, C), (B, D)> {
let get: (A, C) -> (B, D) = { (a, c) in
return (left.get(a), right.get(c))
}
let set: ((A, C), (B, D)) -> (A, C) = { (fst, snd) in
return (left.set(fst.0, snd.0), right.set(fst.1, snd.1))
}
return Lens(get: get, set: set)
}
infix operator *** {
associativity left
precedence 150
}
public func *** <A, B, C, D>(lhs: Lens<A, B>, rhs: Lens<C, D>) -> Lens<(A, C), (B, D)> {
return split(lhs, rhs)
}
// MARK: - Fanout
public func fanout<A, B, C>(left: Lens<A, B>, _ right: Lens<A, C>) -> Lens<A, (B, C)> {
let get: A -> (B, C) = { a in
return (left.get(a), right.get(a))
}
let set: (A, (B, C)) -> A = { (a, input) in
return right.set(left.set(a, input.0), input.1)
}
return Lens(get: get, set: set)
}
infix operator &&& {
associativity left
precedence 120
}
public func &&& <A, B, C>(lhs: Lens<A, B>, rhs: Lens<A, C>) -> Lens<A, (B, C)> {
return fanout(lhs, rhs)
}