[Haskell-beginners] Calculations that might fail: with arrays

[Christopher Howard]

On 06/08/2011 05:56 PM, Antoine Latter wrote:
> Have you tried 'mapM' from the module Control.Monad?
> 
> On Jun 8, 2011 7:10 PM, "Christopher Howard"
> <christopher.howard at frigidcode.com
> <mailto:christopher.howard at frigidcode.com>> wrote:
>> I was wondering if there was a stock function or package in Haskell that
>> allows you to map over a list, but short-circuits the mapping if any of
>> the calculations fail. Say, something like this:
>>
>> -- Don't know if this is a valid signature! :)
>> mapThatCanFail :: (b -> Either a b) -> [b] -> Either a [b]
>>
>> The idea being that, if any calculations fail, the function doesn't
>> bother mapping the rest of the list, but just returns a Left value
>> (error). Otherwise, it returns a Right value containing the new list.
>>
>> I suppose I could try to implement that myself, but it seems like the
>> sort of thing that someone would have thought of already.
>>
>> --
>> frigidcode.com <http://frigidcode.com>
>> theologia.indicium.us <http://theologia.indicium.us>
>>
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Thanks! Works great! You're awesome! :)

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