When should i consider using named parameters against normal parameters?

Question

I was splitting RenameFolder to two pieces and i notice visual studios 2010 supports named parameters! (example below).

I know this has existed for a number of years in other languages. I remember a professor saying why he likes named parameters and that he uses them in all of his code. But i am sure its not in all of his code. I was wondering.

When should i consider to write the function using a named parameter vs normal style (func(a,b,c)). Some cases area (without a when and when not suggestion)

• Calling public methods in the same class
• Calling private methods in the same class
• Calling methods in external 3rd party libraries
• Calling methods in another class in the same namespace
• Calling methods in another class in a different namespace or module

• Calling methods from internal classes not meant to be a library

  public bool RenameFolderIn(PK folderId, string newfoldername)
  {
      return RenameFolder(newfoldername: newfoldername, infolder: true, folderId: folderId);
  }
   public bool RenameFolderOut(PK folderId, string newfoldername)
  {
      return RenameFolder(newfoldername: newfoldername, infolder: false, folderId: folderId);
  }
  public bool RenameFolder(PK folderId, string newfoldername, bool infolder)
  {
  

Answer 1

Typically, I use named parameters when there are a large number of default values and I only need to specify a few non-default, or when the function name doesn't suggest the order of parameters. In the example RenameFolder* functions, I would expect the folder to come before the new name (RenameFolder can be short for the phrase "rename folder folder to name"; phrasing it so the name comes first, if possible, isn't the obvious approach), and so wouldn't bother with named parameters.

Example: suppose Gamma is a constructor for the Gamma distribution, which hase two parameters: shape and scale. There's a statistical convention for passing shape before scale, but the convention isn't obvious from the name, so we use named parameters.

waitTime = Gamma(shape: 2, scale: 2)