[Haskell-beginners] Picking a random element from a Map

[Harald Bögeholz]

Am 26.09.12 10:09, schrieb Daniel Trstenjak:
> 
> Hi Harald,
> 
>> how do I (quickly) pick a random element from a `Data.Map.Map`?
[..]

> M.keys map !! randomValue `mod` M.size map
> 
> But if you need a high performance solution than it's more appropriate
> to put the values into a Data.Vector and indexing into it.

I was hoping to find a solution that makes use of the specific structure
of a map, but now I have written it like this and it works for me:

let (r, gen') = randomR (0, Map.size m - 1) gen
in (Map.keys m !! r, gen')

Thanks for the hint!

Harald

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