First, define a datatype unifying all this config information.

Then there are two simple, common solutions.

If only one or two functions need to be passed the Config data, then just pass it as an argument. If use of the config data is going to be prolific, you might want to consider Reader.

http://stackoverflow.com/questions/14178889/reader-monad-purpose

http://book.realworldhaskell.org/read/programming-with-monads.html

https://hackage.haskell.org/package/transformers-0.4.1.0/docs/Control-Monad-Trans-Reader.html

You could engage in deeper magic than this, but it's not worth it for your use-case.

Hope this helps.

-- Chris

On Tue, Sep 30, 2014 at 3:15 PM, Thomas Koch <thomas@koch.ro> wrote:

Hi,

I wrote my first Haskell 'project', a test suite for my personal SIEVE mail
filter script using dovecots 'sieve-test' tool:

https://github.com/thkoch2001/sieve-test-hs

The file Network/Sieve/Test.hs might actually be interesting as a standalone
library. The most important function is

assertMailActions :: Mail -> Actions -> IO ()

'Actions' is a type that describes the result of running a SIEVE filter over
the passed mail, e.g. store in a certain folder, discard, reject, ...

Somewhere the external process 'sieve-test' is called. At this point I'd like
to make certain things configurable:

- the path and name of the executable
- the parameters for the test-sieve executable
- the name of the sieve script
- the place where to store the temporary mail files
- whether or not to remove the temporary mail files

Does anybody has an idea where I could start to look for a solution?

Thank you,

Thomas Koch
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