Mmm... well, by looking at the type of it I can't infer what you'd do with the returned value of the wrapped function (the action to be mapped): should that last 'a' be a mappend'ed result of all others? or is it the last 'a'? maybe it's meaningless? El mié, 08-06-2011 a las 16:09 -0800, Christopher Howard escribió:
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.