[Haskell-cafe] How to generalize executing a series of commands, based on a list?

[Scott Turner]

On 2010-11-17 21:03, Peter Schmitz wrote:
> I am wondering how to generalize this to do likewise for a
> series of commands, where the varying args (filenames, in this
> case) are in a list ('inOutLeafs').

The 'sequence' function is handy for combining a series of actions, such
as [system cmd1, system cmd2, ...].

> I will also want to accumulate some results; probably just a
> failure count at this time.

'sequence' hangs on to the results. That may be what you need. For
control over accumulating results the good stuff is in Data.Foldable.

> Any advice or pointers to examples would be much appreciated.
> 
> Thanks in advance,
> -- Peter
> 
> 
>> run :: ... -> IO (Int)    -- will return a fail count
>> run
>>    -- some args to this function here...
>>    = do
>>       -- ... set up: inputLeafs, outputLeafs, etc.
>>
>>       -- zip two lists of filenames:
>>       let inOutLeafs = zip inputLeafs outputLeafs
>>
>>       -- the first pair for the first command:
>>       let (inFile1,outFile1) = head inOutLeafs
>>
>>       -- build 1st command using 1st pair of filenames:
>>       let cmd1 = ...
>>
>>       exitCode <- system cmd1
>>       case (exitCode) of
>>          ExitSuccess -> do
>>             putStrLn $ "-- OK."
>>             return 0
>>          ExitFailure failCnt -> do
>>             putStrLn $ "-- Failed: " ++ show failCnt
>>             return 1
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