Swift-only homogeneousnessedness

homogeneousnessedness.swift

extension SequenceType where Generator.Element: Equatable {
    /// Checks every element in a sequence is equal to a given element
    func all(element: Generator.Element) -> Bool {
        return !contains { $0 != element }
    }

    /// Checks no element in a sequence is equal to a given element
    func none(element: Generator.Element) -> Bool {
        return !contains(element)
    }
}

extension String {
    var isHomogeneous: Bool {
        return characters.first.map {
            dropFirst(characters).all($0)
        } ?? true
    }
}

"aaa".isHomogeneous
"abc".isHomogeneous