es-kumagai

protocol P<Element> {
    associatedtype Element
    var first: Element? { get }
}

extension Array : P {
}

let x: any P<Int> = [1, 2]

es-kumagai

protocol P {
    associatedtype Element
}

es-kumagai

// A. 総称関数
func action<Value: P>(_ value: Value) {
}

// B. これは、総称関数？
func action(_ value: P) {
}

es-kumagai

struct MyType<Element> {

    var value: Element
}

es-kumagai

guard var value else {

}

es-kumagai

var values = [1, 2, 3, 4, 5]
var value: Int? { values.popLast() }

while let value {
    print(value)
}

es-kumagai

something(a)        // "some A"
something(b)        // "some A"
something(c)        // "some A"
something(a as A)   // "Any"
something(b as A)   // "Any"
something(c as A)   // "Any"

MemoryLayout.size(ofValue: a)       // 8
MemoryLayout.size(ofValue: b)       // 40
MemoryLayout.size(ofValue: c)       // 40

es-kumagai

protocol A {}
extension Int : A {}

func something(_ value: Any) -> String { return "Any" }
func something(_ value: some A) -> String { return "some A" }

let a: Int = 0
let b: A = 0
let c = a as A

es-kumagai

var value: Int? = 100

do {
    defer {
        value = nil
    }
    
    let value = value.map { $0 * 2 } ?? 0
    print(value)
}

es-kumagai

let possibleNumber = "helloworld"
let convertedNumber = Int(possibleNumber, radix: 36)