adam@5: (** A record inclusion predicate *)
adam@5: 
adam@5: con incl :: K --> {K} -> {K} -> Type
adam@5: 
adam@5: val incl : K --> r1 :: {K} -> r2 :: {K} -> [r1 ~ r2] => incl r1 (r1 ++ r2)
adam@5: val proj : r1 ::: {Type} -> r2 ::: {Type} -> incl r1 r2 -> $r2 -> $r1
adam@5: 
adam@5: val inv1 : K --> nm :: Name -> t :: K -> r :: {K} -> r' :: {K}
adam@5:            -> [[nm] ~ r] =>
adam@5:     f :: (Name -> K -> {K} -> Type)
adam@5:     -> incl ([nm = t] ++ r) r'
adam@5:     -> (nm :: Name -> t :: K -> r :: {K} -> [[nm] ~ r] => f nm t ([nm = t] ++ r))
adam@5:     -> f nm t r'
adam@5: val inv2 : K --> nm :: Name -> t :: K -> r :: {K} -> r' :: {K}
adam@5:            -> [[nm] ~ r] =>
adam@5:     incl ([nm = t] ++ r) r' -> incl r r'
adam@5: 
adam@5: val fold : K --> tf :: ({K} -> Type) -> r ::: {K}
adam@5:            -> (nm :: Name -> v :: K -> r' :: {K}
adam@5:                -> [[nm] ~ r'] => incl ([nm = v] ++ r') r -> tf r' -> tf ([nm = v] ++ r'))
adam@5:            -> tf []
adam@5:            -> folder r -> tf r