On 7/27/07, Eric Y. Kow
Solution #3 No lists, just records (lhs2TeX) ----------------------------------
Advantages: very convenient/compact; have to write (i) Flag type (ii) Settings record type/GetOpt in one go (iii) default Settings easy to lookup flags
Disadvantages: Not as flexible - can't group flags into blocks and have different programs that use different subsets of flags (without sharing the same Setting type) - everything must go into Settings - seems harder to say stuff like 'if flag X is set and flag Y are in the list of Flags, then parameterise flag Z this way' or 'flags X and Y are mutually exclusive'
This is what I'm using for my current project. Most of the disadvantages don't apply in my case, because all my flags are largely-independent simulation parameters. The one thing I find annoying, though, is that for each option I add, I need to make changes in three places: 1) The definition of my options record 2) My default options value 3) My list of GetOpt.OptDescr What I'd really like to be able to do is specify the field name, field type, and GetOpt info in a single place, without any redundancy. This is obviously impossible in vanilla Haskell, so some kind of fancy preprocessing or templating would be necessary. (Sadly, I'm not in a position to pull this off right now.) Stuart