-- The default definition instantiates the type constructor @c@ in
-- the type of 'gfoldl' to the monad datatype constructor, defining
-- injection and projection using 'return' and '>>='.
-- The default definition instantiates the type constructor @c@ in
-- the type of 'gfoldl' to the monad datatype constructor, defining
-- injection and projection using 'return' and '>>='.