I've started learning Scala. I was surprised that next code compiles: object Hello extends App { def isOne(num: Int) = num match { case 1 => "hello" } } You can't do something simi...

Scala can warn when pattern match on a sealed type is not exhaustive, however can we check that a function returns all cases when the return type is sealed? For example, consider the following ADT ...

How do I persuade the Rust compiler that the internal match expression is fine here, as the outer match has already restricted the possible types? enum Op { LoadX, LoadY, Add, } fn test(o: Op)...

I am training for a test tomorrow to complete my introduction to functional programming but there is one thing I don't understand. Whenever I have a program like: test [] = [] test (x:xs) = test ...

So I'm trying to triplize an element, i.e. making 2 other copies of the element. So I've written this: triplize :: [a] -> [a] triplize [x] = concatMap (replicate 3) [x] But I've been getting...

I have no idea why my function doesn't work. I have gone through all the posts about non-exhaustive functions but my functions fulfills all possible options as far as I can see. ascending :: [Int]...

I have the following code {-# LANGUAGE DataKinds, GADTs, TypeOperators #-} data Vect v a where Nil :: Vect '[] a Vec :: a -> Vect v a -> Vect (() ': v) a instance Eq a => Eq (Vect v ...

When I compile the following code with GHC (using the -Wall flag): module Main where data Tree a = EmptyTree | Node a (Tree a) (Tree a) deriving (Show) insert :: (Ord a) => a -> Tree a -&g...

Consider the following broken function: def sum (list : Seq[Int]) : Int = list match { case Nil => 0 case head :: tail => head + sum(tail) } Here, the function was supposed to work with ...

I've got a problem with this code, it should count the longest substring of the same letter in a string, but there is an error: *** Exception: test.hs:(15,0)-(21,17): Non-exhaustive pattern...

This is a follow-up of Why am I getting "Non-exhaustive patterns in function..." when I invoke my Haskell substring function? I understand that using -Wall, GHC can warn against non-exha...

I'm working my way through the book The Haskell Road to Logic, Maths and Programming. (I'm only mid-way through chapter 1, but I'm enjoying it so far and intend to continue.) I've read through the ...