gistfile1.swift

struct Grams {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Kilograms {
        return Kilograms(self.value / 1000)
    }
    
    func __conversion() -> Pounds {
        return Pounds(self.value / 453.592)
    }
}

struct Kilograms {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Grams {
        return Grams(self.value * 1000)
    }
    
    func __conversion() -> Pounds {
        return Pounds(self.value / 2.20462)
    }
}

struct Pounds {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Kilograms {
        return Kilograms(self.value / 2.20462)
    }
    
    func __conversion() -> Grams {
        return Grams((self.value / 2.20462) * 1000)
    }
}

let grams : Grams = Grams(12)
let kiolgrams : Kilograms = grams // 0.012
let pounds : Pounds = grams // 0.026

//similarly
let metricTon = Pounds(2204.62)
let grams2 = metricTon as Grams // 1,000,000
let kilograms2 = metricTon as Kilograms // 1,000

struct Meters {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Cm {
        return Cm(self.value * 100)
    }
    
    func __conversion() -> Inches {
        return Inches(self.value * 39.3701)
    }
    
    func __conversion() -> Feet {
        return Feet(self.value * 3.28084)
    }
}

struct Cm {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Meters {
        return Meters(self.value / 100)
    }
    
    func __conversion() -> Inches {
        return Inches(self.value / 2.54)
    }
    
    func __conversion() -> Feet {
        return Feet(self.value / 30.48)
    }
}

struct Inches {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Meters {
        return Meters(self.value / 39.3701)
    }
    
    func __conversion() -> Feet {
        return Feet(self.value / 12)
    }
    
    func __conversion() -> Cm {
        return Cm(self.value * 2.54)
    }
}

struct Feet {
    var value : Double
    init(_ value : Double) {
        self.value = value
    }
    
    func __conversion() -> Inches {
        return Inches(self.value * 12)
    }
    
    func __conversion() -> Cm {
        return Cm(self.value * 30.48)
    }
    
    func __conversion() -> Meters {
        return Meters(self.value / 3.28084)
    }
}


let yard : Feet = Feet(3)
let inches : Inches = yard // 36.0
let meters : Meters = yard // 0.914
let cm : Cm = yard // 91.44

//similarly
let kilometer = Meters(1000)
let feet = kilometer as Feet // 3,280.84
let cm2 = kilometer as Cm // 100,000
let inches2 = kilometer as Inches // 39,370.1