úÎ5‘ Safe-InferredA  is a  plus a function, , such that: a <> invert a == mempty   invert a < > a == mempty         groups-0.2.0.0 Data.GroupGroupinvertbase Data.MonoidMonoid $fGroup(,,,,) $fGroup(,,,) $fGroup(,,) $fGroup(,) $fGroup(->) $fGroupDual$fGroupProduct $fGroupSum $fGroup()