Swift: Meter conversion using double literals

import Foundation

struct Meter {
    var value: Double
    
    init(_ value: Double) {
        self.value = value
    }
    
    var mm: Double { return value * 1000.0 }
    var km: Double { return value / 1000.0 }
}

extension Meter : FloatLiteralConvertible {
    static func convertFromFloatLiteral(value: Double) -> Meter {
        return Meter(value)
    }
}


let meter: Meter = 100_000.0

meter.mm // => 100,000,000.0
meter.km // => 100.0