[Haskell-beginners] will GHC optimize pattern-matching on integers?

[Patrick Pelletier]

Thanks!  That's exactly what I was hoping.

--Patrick


On 4/13/17 1:41 AM, Rahul Muttineni wrote:
> Hi Patrick,
>
> Yes, this will optimise to "a nice balanced tree of decisions with 
> dense jump tables in the leafs" [1]. You can check out the comments in 
> [1] for more details.
>
> [1] https://github.com/ghc/ghc/blob/master/compiler/cmm/CmmSwitch.hs#L37
>
> Hope that helps,
> Rahul
>
> On Thu, Apr 13, 2017 at 3:55 AM, Patrick Pelletier 
> <code at funwithsoftware.org <mailto:code at funwithsoftware.org>> wrote:
>
>     Suppose I am doing a pattern match on a large number of
>     consecutive (or mostly-consecutive) integers:
>
>     foo 0 = something
>     foo 1 = somethingElse
>     ...
>     foo 1000 = anotherThing
>
>     Will GHC optimize this to a table lookup, or is it going to test
>     each integer in turn?  Am I better off using a Vector or Map
>     instead of pattern matching?
>
>     Thanks,
>
>     --Patrick
>
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>
>
> -- 
> Rahul Muttineni
>
>
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