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

15 May 2013

      Turned out that I didn't need fold at all, just a proper groupBy.

As for these lines

module Main (
...
main
) where
they were generated by Leksah. Do you suggest to remove them? And what
about Leksah as an IDE: do you use it?

Giacomo

On Wed, May 15, 2013 at 9:35 AM, Giacomo Tesio  wrote:
...
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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