in reply to @ 2016-143 12:57 UTCYou can use show as long either there is no read instance or the read instance works for all show output. However, make sure you output something sensible in all cases or debugging outputs might get weird.
Otherwise, you should consider http://hackage.haskell.org/package/text-format-0.3.1.1/docs/Data-Text-Buildable.html