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

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" mailto:christopher.howard@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.

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Thanks! Works great! You're awesome! :) -- frigidcode.com theologia.indicium.us