[Haskell-cafe] ANNOUNCE: set-monad

Tillmann Rendel rendel at informatik.uni-marburg.de
Sun Jun 17 08:26:26 CEST 2012


David Menendez wrote:
> As you noticed, you can get somewhat better performance by using the
> combinators that convert to S.Set internally, because they eliminate
> redundant computations later on.

"Somewhat better"? My example was three times faster, and I guess that 
the fast variant is O(n) and the slow variant is O(n²). So I expect that 
for some applications, the Set interface is more than fast enough and 
the MonadPlus-interface is much too slow.

>> (Why is unioned faster then numbers? Is union doing some rebalancing? Can I
>> trigger that effect directly?)
> It's because mplus a b>>= f turns into mplus (a>>= f) (b>>= f),
> whereas unioned takes the union before calling f.

Here, you compare mplused to unioned, but in the parentheses, I asked 
about numbers and unioned (from my last email).


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