I should perhaps point out that in the development GHC (iirc), there is a library called Data.Sequence which uses 2-3 finger trees to get rather nice efficient sequences. Operations on both ends (appending or dropping) are constant time, while operations in the middle tend to be on the order of the logarithm of the distance to the closer of the two ends. For instance, concatenation and splitting at a point both have complexity proportional to the logarithm of the smaller of the two parts involved. - Cale On 19/04/06, Brian Hulley wrote:

Thanks. I might try this if I don't have any luck with finger trees (from Udo's post), or if they seem too heavy for the simple thing I'm planning to use them for (implementing the text buffer for an edit control which needs a mutable array of lines where each line contains a mutable array of character info). I don't need non-Int indices so your data type for Vector would be fine.

Best regards, Brian.