swift - What is the point of having two different names for the same parameter?

Question

func mapEachElement (inArray arr: [Int],  withFunc aFunc: (Int))

Why would there be "inArray and then "arr"...what's the point?

Same for "withFunc and "aFunc", it makes it more code complicated and also messier to read, why are they even used?

Answer 1

inArray is external name which the caller of the function should use when passing parameters. arr is the internal name which the function implementer uses in the implementation to refer to the parameter. You don't have to supply external name.It makes it more readable. It is more like to make swift function names and parameters readable as Objective-C functions are.