Random float value within range.

RandomBinaryFloatingPoint.swift

extension ClosedRange where Bound: BinaryFloatingPoint {
    var random: Bound {
        let ratio = Bound(arc4random_uniform(UInt32.max)) / Bound(UInt32.max - 1)
        let offset = (upperBound - lowerBound) * ratio
        return lowerBound + offset
    }
}