signature S = sig con nm :: Name con r :: {Type} constraint [nm] ~ r end structure M : S = struct con nm = #A con r = [B = float, C = string] constraint [A] ~ [B] constraint [nm] ~ r constraint [C] ~ [D] end structure M' = struct open M con combo = [nm = int] ++ r end structure M' = struct open constraints M con nm' = M.nm con r' = M.r con combo = [nm' = int] ++ r' end signature S' = sig con r1 :: {Type} con r2 :: {Type} constraint r1 ~ r2 end functor F (M : S) : S' = struct con r1 = [M.nm = int] con r2 = M.r open constraints M constraint r1 ~ r2 end