Don Stewart ha scritto:
manlio_perillo:
Hi.
During a tentative (quite unsuccessfull) to convert a simple Python script that prints on stdout a directory and all its subdirectory [1] in a good Haskell (mostly to start to do real practice with the language), I came across this blog post: http://blog.moertel.com/articles/2007/03/28/directory-tree-printing-in-haske...
Since recently I read about alternatives to lazy IO (like iteratee), I'm curious to know if a flexible, efficient and safe alternative exists, for the task of display a directory tree.
If you can do it with strict IO in Python, do the same thing in Haskell with System.IO.Strict. It should be mechanical to translate Python programs directly into naive IO-based Haskell using strict IO. Boring, but mechanical.
But that's not the purpose of what I'm doing ;). I'm trying to practice with Haskell, by converting small Python scripts I have written. I hope, in future, to write a "big" program in Haskell.
There's no iteratee/fold-based IO system yet.
Yes, I know. By the way, I have managed to have a working program: http://hpaste.org/13919 I would like to receive some advices: 1) I have avoided the do notation, using functions like liftM. Is this a good practice? Is this as efficient as using do notation? 2) I have written some support functions: mapM' and filterM' Are they well written and generic? Are they already available in some package? Can you suggest better names? 3) I find (,) node `liftM` walkTree' path not very readable. Is it possible to express it in a more (not too much) verbose way? Thanks Manlio Perillo