What sort of functions should be provided to access certain newtypes? For instance, consider this: newtype DiffTime = MkDiffTime Integer -- picoseconds It's considered good practice to hide MkDiffTime. At the same time, I need to provide access to the underlying value, so I provide these: timeToSISeconds :: (Real a) => DiffTime -> a siSecondsToTime :: (Real a) => a -> DiffTime These convert with picoseconds by multiplication or division. But do I also want to provide access to the picoseconds directly? timeToSIPicoseconds :: DiffTime -> Integer timeToSIPicoseconds (MkDiffTime ps) = ps siPicosecondsToTime :: Integer -> DiffTime siPicosecondsToTime = MkDiffTime This makes certain other calculations in other modules easier. I have a similar issue with TimeZones. My intention is to encode them as a count of minutes, hide the constructor, but provided minutesToTimeZone and timeZoneToMinutes. Is this sensible? -- Ashley Yakeley, Seattle WA