Re: [Haskell-cafe] All-fail case in asum

I think we're getting a little off track. The point is that the behaviour Yuriy is seeing is inconsistent. Yuriy, can you please post some complete code demonstrating your problem? I have not been able to replicate it. Tom On Fri, Jun 10, 2016 at 11:32:45AM -0400, David Feuer wrote:

Or, to keep it a fold,

asum xs = foldr go (fromMaybe empty) xs Nothing where go x r Nothing = r (Just x) go x r (Just prev) = prev <|> r (Just x) On Jun 10, 2016 11:09 AM, "Dan Burton" wrote:

Add a pattern match for the single-element list to stop it from hitting the empty list base case.

asum [] = empty asum [x] = x asum (x:xs) = x <|> asum xs