Why?
// Because given this array:
let intHolders: [IntHolder] = [...] // type holding `Int` value
// It is cooler to write this:
let sum = intHolders+ // sum has type `Int`
// ...than this:
let sum = intHolders.reduce(0, { $0 + $1.value }) // sum has type `Int` What?
This project makes it convenient to apply addition, subtraction or what ever function you would like to arrays containting Int, Float, Double or your own types!
let integers = [1, 2, 3, 4]
// vanilla sum
let sum = integers.reduce(0, +)
// now
let sum = integers.addition(initial: 0)
// or if initial value is 0
let sum = integers.addition()
// and even shorter, using the power of postfix operator (assuming initial value of zero)
let sum = integers+It does not get much more concise than that.
Custom types
Using reduce with custom types (types with some value of interest) is a bit more work.
struct IntHolder {
let value: Int
init(_ value: Int) { self.value = value }
}
let intHolders = [1, 2, 3, 4].map { IntHolder($0) }
// vanilla sum
let sum = intHolders.reduce(0, { $0 + $1.value })Surely we can sorten it, if we declare this func +
func +(lhs: Int, rhs: IntHolder) -> Int {
return lhs + rhs.value
}Then we can write like this
let sum = intHolders.reduce(0, +)But how fun is that really? And would it not be cool if we could write?
let sum = intHolders.addition(initial: 0)Or in those situations (most cases) where 0 is the initial value:
let sum = intHolders+How?
The only thing you have to do in order to allow this is to write:
extension IntHolder: Adding {}Where the protocol Adding looks like this:
protocol Adding {
associatedtype Value: Addable
var value: Value { get }
}Where Int already conforms to Addable
protocol Identity: Comparable, Equatable {
static var identity: Self { get }
}
protocol Addable: Identity {
static func +(lhs: Self, rhs: Self) -> Self
}
protocol Subtractable: Identity {
static func -(lhs: Self, rhs: Self) -> Self
}
typealias Countable = Identity & Addable & Subtractable
extension Int: Countable {
static var identity: Int = 0
}
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