Default parameters

Sometimes, it is convenient to provide default values for parameters in a function. Let's say that we want to create a thread pool. The parameter to set the number of threads could default to the number of CPU cores. This would be a sensible default, but the user might still want to use something different.

The way to achieve this in languages without default parameters is to offer overloaded versions of the same function:

    fun createThreadPool(): ExecutorService { 
      val threadCount = Runtime.getRuntime().availableProcessors() 
      return createThreadPool(threadCount) 
    } 
 
    fun createThreadPool(threadCount: Int): ExecutorService { 
      return Executors.newFixedThreadPool(threadCount) 
    } 

Here, the user can now choose which version to invoke. However, the number of parameters sometimes means that we end up with many overloaded variations...