[Haskell-beginners] Processing a list of files the Haskell way

[Michael Schober]

Hi again,

I'm still trying to figure out my earlier problem regarding the 
directory tree and functions on the files.

What I'm really trying to do sounds simple enough: find duplicate files 
for a complete directory, given a root. The original approach I had in 
mind was to compute every file's checksum, which I could feed into a map 
of (checksums,[filepaths]).

On 03/10/2012 01:48 PM, Chaddaï Fouché wrote:
> Note that you solution isn't very "functional-like", but rather
> imperative. On the other hand, making it more functional in this
> particular case come with its own brand of subtle difficulties.

I now wonder how to achieve my goal properly in Haskell. Obviously I 
have some sequential parts of my program (reading directory trees is I/O 
and therefore monadic), but it seems to me that could also be some 
functional part as well (pairing files with checksums, pairing checksums 
with common filepaths, filtering only checksums with more than one 
filepath, maybe even sorting, etc.).

How would you go about to do it? Which parts of the program should be 
monadic, which functional? Would you create a custom-build monad or 
would you use build-ins (which ones?)?

I would really like to have some pointers how an experienced Haskell 
developer would go about such a thing, since I want to acquire a Haskell 
feel of programming rather than keep on programming in my old ways, now 
in Haskell. I would also be happy to be simply pinpointed to other 
applications which source code are exemplary, but not too huge to dig 
through in a sensible amount of time. (I'm currently trying to work 
through the Darcs source code, but that seems a bit too overkill.)

Thanks for any comments and thoughts.

Best,
Michael