Re: List syntax (was: Re: help from the community?)

On 2007 Feb 2, at 12:13 PM, Kirsten Chevalier inquired:

On 2/2/07, Douglas Philips wrote:

...

I assert that the trailing comma is a feature, not a programmer forgetting "the last element", and that this is already explicitly allowed, as per the syntax fragments already quoted, repeated here for convenience:

-- from: http://www.haskell.org/onlinereport/syntax-iso.html#sectB.4 impspec -> ( import1 , ... , importn [ , ] ) (n>=0) | hiding ( import1 , ... , importn [ , ] ) (n>=0) exports -> ( export1 , ... , exportn [ , ] ) (n>=0)

Huh? I don't quite see what you're getting at here. The report says that the trailing comma is allowed in import and export lists, yes. But you were talking about trailing commas in lists and tuples, which would be a change to the existing language, not something that's "already explicitly allowed". Can you clarify what you meant?

Hmmm...stated another way: I am proposing that the list and tuple syntax change to be consistent with the import and export syntax. The argument that a trailing comma "means" "the programmer forgot the last item" in a list / tuple is inconsistent with the deliberately explicit permissiveness of a trailing comma in the import / export lists. In the import / export lists such a trailing comma does not mean "programmer forgot additional thing at the end." --D'gou