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Today's Topics:
1. Re: will GHC optimize pattern-matching on integers?
(Patrick Pelletier)
----------------------------------------------------------------------
Message: 1
Date: Thu, 13 Apr 2017 19:11:31 -0700
From: Patrick Pelletier <c...@funwithsoftware.org>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] will GHC optimize pattern-matching on
integers?
Message-ID: <a7be8316-d68e-64ca-f946-268d40fc0...@funwithsoftware.org>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
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
> <c...@funwithsoftware.org <mailto:c...@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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