[Haskell-beginners] How to improve lazyness of a foldl (and memory footprint)

[Giacomo Tesio]

Thanks a lot!

Yesterday on freenode's #haskell channel Cane noted how my laziness problem
reside in the foldl use in foldTradingSample.
I have to turn it into a foldr (but I'm still unsure how...)


Giacomo


On Wed, May 15, 2013 at 12:46 AM, Henk-Jan van Tuyl <hjgtuyl at chello.nl>wrote:

> On Tue, 14 May 2013 11:22:27 +0200, Giacomo Tesio <giacomo at tesio.it>
> wrote:
>
>  Hi, I'm trying to improve a small haskell program of mine.
>>
> :
>
> Some remarks:
>
> 0) Use hlint (available on Hackage) for improvement suggestions
> 1) You don't have to write the module heading in Main.hs, it is not a
> library (why export main?)
> 2) Change "print" to "putStrLn" if you want to display messages without
> quotes
> 2) switchArgs is only partially defined, add something like:
>      switchArgs [x] = putStrLn $ "Unknown tool: " ++ x
> 3) Use shorter lines, for example change:
>
>   importTrades outDir csvFile = transformFile csvFile (foldTradingSample.*
> *getTickWriteTrades)   (saveTradingSamples outDir)
>
> to:
>
>   importTrades outDir csvFile =
>     transformFile
>       csvFile
>       (foldTradingSample.**getTickWriteTrades)
>       (saveTradingSamples outDir)
> 4) It is considered good practice, to write the function
>    composition operator between spaces (change f.g to f . g)
>
> I have analyze your software further to see how sufficient laziness can be
> reached.
>
> Regards,
> Henk-Jan van Tuyl
>
>
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