sortBy is no longer a good consumer in GHC 7
|Reported by:||lpsmith||Owned by:||igloo|
|Type of failure:||Documentation bug||Test Case:|
|Related Tickets:||Differential Rev(s):|
The List Fusion section of the GHC User's Guide lists
sortBy as a good consumer.
In past versions of GHC,
sortBy turned its input into a list of lists to be merged by using
map (:), which is why it was a good consumer. However this is somewhat arguable, as it's only a good consumer in a weak sense of the word. When it comes to doing the real work of the algorithm, sort was never a good consumer.
However, in GHC 7,
sortBy breaks its input into monotonic runs, producing a shorter outer list. This is not a good consumer in any sense of the word.