Data.Map documentation lacks a bit of precision

Jesper Louis Andersen jlouis at
Mon Apr 4 17:20:01 EDT 2005

I am not sure this is the correct mailing list. But the old Data.FiniteMap
implementation states for the function ``addToFM'' (in the haddock

Adds an element to a FiniteMap. Any previous mapping with the same key is 

Whereas the equivalent ``insert'' in the new Data.Map module States:

O(log n). Insert a new key and value in the map.


I think it is good that there now is a running time asymptotic bound, but
I do not know what happens if the (key, value) pair is already there. There
is no information about this in the haddock documentation at all. It could
either overwrite silently, or it could raise some kind of error. Both
options are plausible, since one could just use ``Data.Map.adjust'' like:

f :: Ord k -> k -> a -> Map k a -> Map k a 
f k a fm = Data.Map.adjust (\_ -> a) k fm

And gain the explicit behaviour. I do not currently have a GHC 6.4
installed here, so I cannot test this behaviour, but some code I am working
on needs to be fairly compatible. Therefore we have a layer on top of 
Data.FiniteMap which implements the new map structure. This difference just
caught my eye. It also makes it rather hard to update the documentation 
myself and provide a patch. Where is the official repository located?


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