-- canonical order of the components of a module pair
--
canon :: ModulePair -> (Module, Module)
canon (ModulePair m1 m2) | m1 < m2   = (m1, m2)
                         | otherwise = (m2, m1)
canon :: ModulePair -> (Module, Module)
canon (ModulePair m1 m2) | m1 < m2   = (m1, m2)
                         | otherwise = (m2, m1)
canon (ModulePair m1 m2) | m1 < m2   = (m1, m2)
                         | otherwise = (m2, m1)