[Grace-core] A curiosity of methods with variable arity parameter lists

[Andrew P. Black]

While working with mgcollections.set, Jameson and I noticed a curiosity.

If you have a method 

	withAll(items:Collection<Dynamic>) 

and you want to write a method 

	with(*items:Dynamic)

then it's easy:

	method with(*items:Dynamic) { self.withAll(items) }

On the other hand, if you have with(), and want to write withAll(), then there is no way to do it without using reflection.  Even then, the code is messy; this was what I came up with:

	method withAll(items:Collection<Dynamic>) {
		def selfMirror = mirror.reflect(self)
		def argLists = list.with(items)
		def withMethod = selfMirror.forMethod "with"
		withMethod.request(argLists)
	}

The moral of the story, I think, is that we should make it a practice in defining library interfaces never to define a variable arity method directly, but instead to always define a method that takes an array of arguments, and then to define the varArity method in terms of that (as I did above for method "with").  Notice that the bodies of withAll and with are identical: in both cases, items is a Collection.

	Andrew
 
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