On Tue, May 30, 2006 at 10:33:05PM +0100, Brian Hulley wrote:
I was kind of hoping that the syntax of Haskell could be changed so that for any sequence of characters there would be a unique parse that had a minimum number of "gaps" inserted by the editor to create a complete parse tree, and moreover that this parse could be found by deterministic LL1 recursive descent.
a problem is that people don't write code like they write novels. At least I don't. I skip around, adding the beginning and ending of functions and going back and filling in the center, or writing the => first, then the type and going back and filling in the context. or taking existing code and changing it in pieces, deleting something there, adding it somewhere else, changing names, all of which leave intermediate states that arn't just truncated programs. I don't see such a property actually helping that much in terms of this problem. I think you have no choice but to use heuristics to decide what the user intends and try to limit the scope of potentially incomplete source souring later things typed. Although not as popular as they once were, error correcting parsers is a fairly advanced field in computer science, combined with the knowledge of what names are in scope, I think you can come up with fairly robust heuristics. It is by no means a trivial problem, but it is certainly a tractable one. John -- John Meacham - ⑆repetae.net⑆john⑈