pattern_matching.swift

func ~=<T>(rhs: KeyPath<T, Bool>, lhs: T) -> Bool {
    lhs[keyPath: rhs]
}

func handle(_ character: Character) {
    switch character {
    case "<":
        print("element")
    case "#":
        print("hashtag")
    case \.isNumber:
        print("number")
    case \.isNewline:
        print("new line")
    default:
        print("others")
    }
}

var a: Character = "3"
handle(a)
if case \.isNumber = a {
    print("numberi still matched")
}

a = "\n"
handle(a)
if case \.isNewline = a {
    print("new line still matched")
}

a = "#"
handle(a)
if case "#" = a {
    print("hashtag still matched, but not matching self-defined pattern `~=<T>(rhs: KeyPath<T, Bool>, lhs: T) -> Bool`")
}



// output:
// number
// numberi still matched
// new line
// new line still matched
// hashtag
// hashtag still matched, but not matching self-defined pattern `~=<T>(rhs: KeyPath<T, Bool>, lhs: T) -> Bool`