Reid Barton questions

Reid Barton answers

• Use cases of 'signum' for ordered numeric types in Haskell
• GHC undefined reference to Paths in dependency
• Applicative instance for hypercuboid
• In Haskell how can I match a type class with an instance of that type class?
• catch violates the semantic approximation order?
• Getting value with a Lens s t a b
• Polymorphic "flip" fails in 7.10
• What is the Addr# type, and how can I use it?
• haskell fmap . fmap function, function over two functors
• Order of execution with Haskell's `mapM`