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

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 wrote:

On Tue, 14 May 2013 11:22:27 +0200, Giacomo Tesio 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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