Recursion with Swift Coroutines

coroutines-recursion.swift

import Foundation
class Tree {
    let left, right: Tree?
    init(left: Tree?, right: Tree?) {
        self.left = left
        self.right = right
    }
}

let tree = (1..<100000000).reduce(Tree(left: nil, right: nil), { prev, result in
    Tree(left: prev, right: nil)
})

struct AsyncResursiveFunction<Input, Output> {
    let closure: (Input, Self) async -> Output
    func callAsFunction(_ input: Input) async -> Output {
        await closure(input, self)
    }
}

let asyncDepth = AsyncResursiveFunction<Tree?, Int> { tree, callRecursive in
    guard let tree = tree else { return 0 }
    return await 1 + max(callRecursive(tree.left), callRecursive(tree.right))
}

func depth(_ tree: Tree?) -> Int {
    guard let tree = tree else { return 0 }
    return 1 + max(depth(tree.left), depth(tree.right))
}

@main struct Main {
  static func main() async {
      await print(asyncDepth(tree))
      // depth(tree) recursive stack overflow
  }
}