RULES

[jkarni]

Adding RULES would be great, but GHC isn't happy. E.g.:

  {-# RULES  "set/set" forall a b field book. set field a (set field b book) = set field a book
  #-}

/home/jkarni/Documents/progs/bookkeeper/src/Bookkeeper.hs:49:68: error:
    • Couldn't match type ‘Data.Type.Map.Nub
                             ((Data.Type.Set.Sort
                                 (Data.Type.Set.Filter
                                    'Data.Type.Set.FMin
                                    (field 'Data.Type.Map.:-> val1)
                                    (Data.Type.Map.Nub
                                       (Data.Type.Set.Sort (old Data.Type.Map.:\ field))))
                               Data.Type.Set.:++ '[field 'Data.Type.Map.:-> val1])
                              Data.Type.Set.:++ Data.Type.Set.Sort
                                                  (Data.Type.Set.Filter
                                                     'Data.Type.Set.FMax
                                                     (field 'Data.Type.Map.:-> val1)
                                                     (Data.Type.Map.Nub
                                                        (Data.Type.Set.Sort
                                                           (old Data.Type.Map.:\ field)))))’
                     with ‘Data.Type.Map.Nub
                             ((Data.Type.Set.Sort
                                 (Data.Type.Set.Filter
                                    'Data.Type.Set.FMin
                                    (field 'Data.Type.Map.:-> val1)
                                    (Data.Type.Map.Nub
                                       (Data.Type.Set.Sort
                                          (Data.Type.Map.Nub
                                             ((Data.Type.Set.Sort
                                                 (Data.Type.Set.Filter
                                                    'Data.Type.Set.FMin
                                                    (field 'Data.Type.Map.:-> val)
                                                    (Data.Type.Map.Nub
                                                       (Data.Type.Set.Sort
                                                          (old Data.Type.Map.:\ field))))
                                               Data.Type.Set.:++ '[field 'Data.Type.Map.:-> val])
                                              Data.Type.Set.:++ Data.Type.Set.Sort
                                                                  (Data.Type.Set.Filter
                                                                     'Data.Type.Set.FMax
                                                                     (field 'Data.Type.Map.:-> val)
                                                                     (Data.Type.Map.Nub
                                                                        (Data.Type.Set.Sort
                                                                           (old
                                                                            Data.Type.Map.:\ field)))))
                                           Data.Type.Map.:\ field))))
                               Data.Type.Set.:++ '[field 'Data.Type.Map.:-> val1])
                              Data.Type.Set.:++ Data.Type.Set.Sort
                                                  (Data.Type.Set.Filter
                                                     'Data.Type.Set.FMax
                                                     (field 'Data.Type.Map.:-> val1)
                                                     (Data.Type.Map.Nub
                                                        (Data.Type.Set.Sort
                                                           (Data.Type.Map.Nub
                                                              ((Data.Type.Set.Sort
                                                                  (Data.Type.Set.Filter
                                                                     'Data.Type.Set.FMin
                                                                     (field 'Data.Type.Map.:-> val)
                                                                     (Data.Type.Map.Nub
                                                                        (Data.Type.Set.Sort
                                                                           (old
                                                                            Data.Type.Map.:\ field))))
                                                                Data.Type.Set.:++ '[field
                                                                                    'Data.Type.Map.:-> val])
                                                               Data.Type.Set.:++ Data.Type.Set.Sort
                                                                                   (Data.Type.Set.Filter
                                                                                      'Data.Type.Set.FMax
                                                                                      (field
                                                                                       'Data.Type.Map.:-> val)
                                                                                      (Data.Type.Map.Nub
                                                                                         (Data.Type.Set.Sort
                                                                                            (old
                                                                                             Data.Type.Map.:\ field)))))
                                                            Data.Type.Map.:\ field)))))’
        arising from a use of ‘set’
      NB: ‘Data.Type.Map.Nub’ is a type function, and may not be injective
    • In the expression: set field a book
      When checking the transformation rule "set/set"
    • Relevant bindings include
        a :: val1 (bound at src/Bookkeeper.hs:49:19)
        b :: val (bound at src/Bookkeeper.hs:49:21)
        field :: Key field (bound at src/Bookkeeper.hs:49:23)
        book :: Book' old (bound at src/Bookkeeper.hs:49:29)