Algebraic Data Types (ADTs) in Haskell can automatically become instances of some typeclasses (like Show, Eq) by deriving from them. data Maybe a = Nothing | Just a deriving (Eq, Ord) My questi...

Precisely, why does B b = (B&) a compile and work whereas B b = (B) a does not in the below program? #include <iostream> using namespace std; class A {public: void f(){ cout<<"A"&...

I am using ghci, this code section newtype Gold = Gold Int deriving (Eq, Ord, Show, Num) is showing the error as Can't make a derived instance of 'Num Gold': 'Num' is not a derivable class ...

Suppose I have the following code: {-# LANGUAGE GADTs, DeriveDataTypeable, StandaloneDeriving #-} import Data.Typeable class Eq t => OnlyEq t class (Eq t, Typeable t) => BothEqAndTypeable t...

I now know there is no protected method in Objective-C and here is my problem. I have two viewControllers with many functions and properties that are shared. My vision was to have a BaseViewControl...

I have been trying out the Vinyl package, which uses type level kinds to create record structures with field level polymorphism and automatically provided lenses. Both of these features would be ve...

I am ploughing through Learn You a Haskell for Great Good, and I have reached up to section 8.4, "Derived Instances". In this section, there's the following data type declaration: data Person = Pe...

When working with derived instances in Haskell, is it possible to derive functions for arbitrary types, or are we restricted to particular functions?