Hello,

I use appendmap in order to gather results from an sql query and I used group by clause in order to sort the results. I observed that AppendMap do not conserve the group by order of my results, but instead sorts my results by the apppend key provided to the AppendMap.

Feature Proposal

I would like to know if this is a possible to make AppendMap conserve the input order of the elements to be appended.

Actual behavior

let one = AppendMap $ Map.fromList [(2, "hello"), (1, "goodbye")]
let two = AppendMap $ Map.fromList [(3, "world"), (1, "again")]
print $ unAppendMap (one <> two) -- fromList [(1,"goodbyeagain"),(2,"hello"),(3,"world")]

New behavior

let one = AppendMap $ Map.fromList [(2, "hello"), (1, "goodbye")]
let two = AppendMap $ Map.fromList [(3, "world"), (1, "again")]
print $ unAppendMap (one <> two) -- fromList [(2,"hello"),(1,"goodbyeagain"), (3,"world")]

The Map type has instances for Data and Typeable, but the wrapper doesn't. I can't think of a good reason for that.