class People{

    let firstName : String
    let lastName : String

    var fullName : String{
        get{
            return firstName + " " + lastName;
        }
    }
    var age : Int

    init(firstName : String, lastName : String, age : Int){
        self.firstName = firstName
        self.lastName = lastName
        self.age = age

    }
}

let p1 = People(firstName: "first P1", lastName: "last P1", age: 10)
let p2 = People(firstName: "first P2", lastName: "last P2", age: 20)

let peoples = [p1,p2]

/// vairable with for loop
extension Array where Element : People{

    var averageAge : Int {

        var totalAge = 0;

        for people in self{
            totalAge += people.age
        }

        return totalAge / self.count;

    }
}

print( peoples.averageAge)

// vairable with reduce
extension Array where Element : People{

    var averageAgeWithReduce : Int {

        let totalAge = self.reduce(0){ (result, next )->Int in

            return result + next.age

        }

         return totalAge / self.count


    }
}

print( peoples.averageAgeWithReduce)



// method with reduce
extension Array where Element : People{

    func averageAgeWithMethod() -> Int {

        let totalAge = self.reduce(0){ (result, next )->Int in

            return result + next.age

        }

        return totalAge / self.count

    }
}

print( peoples.averageAgeWithMethod())