For a given block of code, calculates the execution time.

ExecutionTime.swift

func executionTimeInterval(block: () -> ()) -> CFTimeInterval {
    let start = Date() // <<<<<<<<<< Start time
    block()
    let end = Date()   // <<<<<<<<<<   end time
    let timeInterval: Double = end.timeIntervalSince(start);
    print(timeInterval)
    return timeInterval
}

//Example of use
executionTimeInterval { for _ in 0..<10 { } }