gistfile1.txt

//: Playground - noun: a place where people can play

import UIKit

protocol Incable {
    func inc () -> Incable
}

class DoubleWrapper : Incable {
    let number: Double
    init(number: Double) {
        self.number = number
    }
    func inc() -> Incable {
        return DoubleWrapper(number: self.number + 1)
    }
}

class IntWrapper : Incable {
    let number: Int
    init(number: Int) {
        self.number = number
    }
    func inc() -> Incable {
        return IntWrapper(number: self.number + 1)
    }
}

func incer (incable: Incable) -> Incable {
    return incable.inc()
}

func inctuple(incingfunc: (Incable) -> Incable) -> (DoubleWrapper, IntWrapper) {
    // Error: Cannot convert return expression of type (Incable, Incable)
    // to return type (DoubleWrapper, IntWrapper)
    return (incingfunc(DoubleWrapper(1.5)), incingfunc(IntWrapper(5)))
}