This is a variation on an old chestnut. I wrote it expecting it not to work, but it did. Or is it dodgy? (At GHC 8.6.5.) {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, F...

I'm currently dealing with some Haskell code that I didn't write, but that I've made changes to. After my changes, I run the program and get the following error message: Prelude.!!: index too larg...

I'm trying to show something of type Tagged s b (Data.Tagged) in a module that also imports from the accelerate library. Unfortunately, the accelerate library defines the show instance instance Ki...

At times, I run into the "feature" that Haskell only matches instance heads, namely, instance (a ~ NewDataTyp b) => C a will now match any type whatsoever, i.e. writing another instance decla...

I have the following typeclass which models a SQL-like query optimization: class OptimizableQuery q where type Optimized q :: * optimize :: q -> Optimized q instance Query q => Optimizabl...