Glynn Clements
Read-only or write-only attributes could be implemented by throwing an error for prohibited operations. Read-only attributes could be implemented by simply ignoring write operations.
If there is an alternative design which would allow errors to be reported statically (e.g., by using the typesystem or by not providing a 'set' operation for the offending attribute or whatever), then I think it would be significantly better. One of Haskell's huge strengths is that static error detection catches so many errors that would otherwise make it through to be caught by (dynamic) testing or included in released systems. -- Alastair Reid alastair@reid-consulting-uk.ltd.uk Reid Consulting (UK) Limited http://www.reid-consulting-uk.ltd.uk/alastair/