[Haskell-cafe] Why no merge and listDiff?

[Will Ness]

Hello cafe,

I wonder, if we have List.insert and List.union, why no List.merge (:: Ord a => 
[a] -> [a] -> [a]) and no List.minus ? These seem to be pretty general 
operations.

Brief look into haskell-prime-report/list.html reveals nothing.

Could we please have them?

On the wider perspective, is their a way to declare an /ordered/ list on the 
type level (e.g. [1,2,3] would be one, but not [2,3,1])? Non-decreasing lists? 
Cyclical, or of certain length? What are such types called?

TIA!