Re: [Haskell-cafe] ghc should be able to deduce correct use of partial functions and not give a warning in such cases

On Sat, 20 Apr 2024, George Colpitts wrote:

Thanks for everybody's replies

To give more context the original code from Ch. 12 of Bird's Thinking Functionally with Haskell was:

let (xs, ys) = break (== ch) str in

         if null ys then [] else [(xs, tail ys)])

I replaced it with 

let (xs, ys@(_ : t)) = break (== ch) str in

         if null ys then [] else [(xs, t)])

This won't work. ys@(_ : t) only matches on non-empty lists. It will also give you warnings, but this warning may not be contained in -Wall depending on the GHC version.