Simon Marlow wrote (snipped):
I agree it's not worth arguing, it's more important to decide whether we can implement Read Version.
Why is the Read instance for Version so important? I don't really see one using it much. The only occasion I can imagine when you would actually want to create a Version value for GHC is when you send a new release out the door.
I don't really the instance of Ord being that important either. What one wants to know is whether (1) version X was released later than some given date; (2) version X is lexicographically subsequent to [sequence of integers] (so GHC 6.02.1 comes after GHC 4.08.1); (3) version X is a subversion of [sequence of integers], as 6.2.1 is a subversion of 6.2; (4) version X has a tag attached meaning "DANGER. Do not use unless your name is Simon".
I see - I assumed you were planning to have Ord and Read instances for Version and compare versions by doing if ghc_version => read "6.2" then ... but you'd do it like this: if branch ghc_version >= [6,2] then ... which is fine. In fact, I think I like yours better :-) I'm not convinced of the need to have a date attached to all versions, though. Under what circumstances do you imagine needing (1) above, where (2) won't do? Cheers, Simon