Re: [Haskell-cafe] List concat

Andrew Coppin wrote:

The function (++) :: [x] -> [x] -> [x] has O(n) complexity.

If somebody were to invent some type that looks like [x] but actually uses some sort of tree rather than a linked list, you should be able to get O(1) concatenation. Has anybody ever implemented such a thing?

See also Data.Sequence, which is not O(1) append, but it is O(log something), and also O(1) cons and snoc and has lots of other nice complexities including fast update of a single cell. Jules