non-exhaustive-patterns

Non-exhaustive patterns in function [duplicate]

December 14, 2023 by Tarik

It looks like you’re missing the case where there’s a one element list: countLongest’ n max (y:ys) | … etc. … | otherwise = …. Here’s a contrived example similar to yours: f [] = 3 — matches an empty list f (a:b:bs) = 4 — matches a list with at least two elements Examples: … Read more

In Haskell, why non-exhaustive patterns are not compile-time errors?

December 3, 2023 by Tarik

There are cases where you don’t mind that a pattern match is non-exhaustive. For example, while this might not be the optimal implementation, I don’t think it would help if it didn’t compile: fac 0 = 1 fac n | n > 0 = n * fac (n-1) That this is non-exhaustive (negative numbers don’t … Read more