changeCalculus calc calc' =
 case rcalc' of
   [] -> (calc,   "new calculus not recognized\n")
   _  -> (rcalc', "new calculus has" +++ show (length rcalc') +++ "rules\n")
  where rcalc' = rulesOfCalculus calc'
changeCalculus calc calc' =
 case rcalc' of
   [] -> (calc,   "new calculus not recognized\n")
   _  -> (rcalc', "new calculus has" +++ show (length rcalc') +++ "rules\n")
  where rcalc' = rulesOfCalculus calc'
changeCalculus calc calc' =
 case rcalc' of
   [] -> (calc,   "new calculus not recognized\n")
   _  -> (rcalc', "new calculus has" +++ show (length rcalc') +++ "rules\n")
  where rcalc' = rulesOfCalculus calc'