On Sat, May 07, 2005 at 10:56:11PM +0200, Benjamin Franksen wrote:
It would be a great improvement if Haskell's standard library (including the Prelude) would provide a uniform framework for collections, and in particular sequences (linear collections, indexed by natural numbers), and there should be standard implementations that don't favour operations on the left end over those on the right end. It is a shame that a language like Haskell doesn't even have a Deque (double ended queue) in the its standard library.
Robert Will has proposed a new unified standard for collections (as well as some default implementations) with above properties (and a lot more). IMHO, his work is (at least) a very good starting point and deserves more attention.
There was some discussion of this on the libraries list last year: http://www.haskell.org//pipermail/libraries/2004-April/thread.html http://www.haskell.org//pipermail/libraries/2004-June/thread.html (look for "sequences"). The background was that most people (Robert was an exception) thought that a general collection framework wasn't the way to go, partly because the proposals needed non-H98 features but mainly because there was no clear best choice, so a few concrete implementations (Data.Set, Data.Map, Data.IntSet and Data.IntMap) were added. However sequences can be described by a H98 class, and are also the area where a class with several instances is most useful.