[Haskell-cafe] Re: Write Haskell as fast as C.
andrewcoppin at btinternet.com
Sun May 18 12:21:44 EDT 2008
Ketil Malde wrote:
> Ketil Malde <ketil at malde.org> writes:
>>> data EvidenceCode = IAC | IUG | IFR | NAC | NR | ... deriving Show
>> Could it be that this derived read instance is somehow very inefficient?
> To answer my own question: this is exactly it, ghc derives less than
> optimal code in this case. Rather than reiterate the case here, I did
> a quick writeup at http://blog.malde.org/, and would be quite happy
> about any feedback or suggestions.
I think you'll find the code that GHC derives for a Read instance
handles extra whitespace and all kinds of other whatnot that you don't
actually need in this specific case. I suspect this is what's up - but I
don't have any hard proof for that. ;-)
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