Re: updateLookupWithKey bug? Was: Data.Map, Data.IntMap documentation (1611)

And sounds like we need some QuickCheck properties too! apa3a:

I started to update documentation for Data.IntMap. I found a discrepancy between the modules' updateLookupWithKey behavior right in the area brought to my attention earlier:

--- Andriy Palamarchuk wrote:

...

* As per

http://www.haskell.org/pipermail/libraries/2007-March/007304.html

...

added following information to the description of updateLookupWithKey:

The function returns changed value, if it is updated. Returns the original key value if the map entry is deleted.

The test case:

...

:m Data.Map let f k x = if x == "a" then Just ((show k) ++ ":new a") else Nothing updateLookupWithKey f 5 (fromList [(5,"a"), (3,"b")])

(Just "5:new a",fromList [(3,"b"),(5,"5:new a")])

...

:m Data.IntMap updateLookupWithKey f 5 (fromList [(5,"a"), (3,"b")])

(Just "a",fromList [(3,"b"),(5,"5:new a")])

The problem here is that Data.Map.updateLookupWithKey returns the *updated* value, but Data.IntMap.updateLookupWithKey returns the value *before* update.

Please agree on the behavior, fix the bug and let me know what to write in the docs. Thanks, Andriy

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