Parameterized version of (<>) in Semigroup If used in
conjunction with
Empty, ie as a parameterized Monoid, then the
instance should follow the following laws: *
pmempty'
pmappend' x = x *
x pmappend' pempty' =
x *
x pmappend' (y pmappend' z) = (x
pmappend' y) pmappend' z