A protocol to use when you want to write a generic function that can accept Ints, Floats or Doubles.

MathematicsProtocol

protocol MathematicsProtocol: Equatable, Comparable, IntegerLiteralConvertible {
    init(_ value: Int)
    init(_ value: Float)
    init(_ value: Double)
    
    func +(lhs: Self, rhs: Self) -> Self
    func -(lhs: Self, rhs: Self) -> Self
    func * (lhs: Self, rhs: Self) -> Self
    func / (lhs: Self, rhs: Self) -> Self
}
extension Int: MathematicsProtocol {}
extension Float: MathematicsProtocol {}
extension Double: MathematicsProtocol {}

// Equatable means you can use ==
// Comparable means you can use < > <= >=
// IntegerLiteralConvertible means you can use integer literals 

// Credit to
// http://stackoverflow.com/questions/27321763/return-int-from-a-generic-mathematics-type-in-swift
// http://stackoverflow.com/questions/25592838/generics-of-raw-types-int-float-double-create-weird-error-messages