Support Swift 3

Meter.swift

import Foundation

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

extension Meter : ExpressibleByFloatLiteral {
    
    public init(floatLiteral value: Double) {
        self = Meter(value)
    }
}

extension Meter : ExpressibleByIntegerLiteral {
    
    public init(integerLiteral value: Int) {
        self = Meter(Double(value))
    }
}

extension Meter : CustomStringConvertible {
    
    public var description: String {
        return value.description
    }
}

extension Meter : CustomDebugStringConvertible {
    
    public var debugDescription: String {
        return value.debugDescription
    }
}

extension Meter : LosslessStringConvertible {
    
    public init?(_ text: String) {
        if let doubleValue = Double(text) {
            self = Meter(doubleValue)
        } else {
            return nil
        }
    }
}

prefix public func +(x: Meter) -> Meter {
    return Meter(x.value)
}

prefix public func -(x: Meter) -> Meter {
    return Meter(-x.value)
}

public func +(lhs: Meter, rhs: Meter) -> Meter {
    return Meter(lhs.value + rhs.value)
}

public func -(lhs: Meter, rhs: Meter) -> Meter {
    return Meter(lhs.value - rhs.value)
}

public func *(lhs: Meter, rhs: Meter) -> Meter {
    return Meter(lhs.value * rhs.value)
}

public func /(lhs: Meter, rhs: Meter) -> Meter {
    return Meter(lhs.value / rhs.value)
}

public func +=(lhs: inout Meter, rhs: Meter) {
    return lhs.value += rhs.value
}

public func -=(lhs: inout Meter, rhs: Meter) {
    return lhs.value -= rhs.value
}

public func *=(lhs: inout Meter, rhs: Meter) {
    return lhs.value *= rhs.value
}

public func /=(lhs: inout Meter, rhs: Meter) {
    return lhs.value /= rhs.value
}