Haskell beginner here. I've defined the following types: data Nat = Z | S Nat data Vector a n where Nil :: Vector a Z (:-) :: a -> Vector a n -> Vector a (S n) infixl 5 :- I'm trying to write the function, takeWhileVector which behaves the...

As a learning experience, I'm trying to implement a verified regular-expression matcher using continuation-passing style in Agda, based on the one proposed in this paper. I've got a type for regular expressions defined like this: data RE : Set where ε : RE ∅ : RE Lit : Char ->...

I am trying to do the following trait Stateful { type State } case class SystemState(system: Stateful, state: system.State) // does not compile That is, the type of statedepends on (the value of) system. That, however, is not supported: illegal dependent method type: parameter appears in the type of another...

Perhaps this is a stupid question. Here's a quote from the Hasochism paper: One approach to resolving this issue is to encode lemmas, given by parameterised equations, as Haskell functions. In general, such lemmas may be encoded as functions of type: ∀ x1 ... xn. Natty x1 → ... →...

I am implementing a simple dependently-typed language, similar to the one described by Lennart Augustsson, while also using bound to manage bindings. When typechecking a dependent lambda term, such as λt:* . λx:t . x, I need to: "Enter" the outer lambda binder, by instantiating t to something Typecheck λx:t...

I have some experience using Coq and am now in the process of learning Agda. I'm working on a correctness proof of insertion sort and have reached a point where I would like to perform something similar to Coq's rewrite tactic. Currently, I have: open import Data.Nat open import Relation.Binary.PropositionalEquality...

I've been experimenting with Idris and it seems like it should be simple to specify some sort of type for representing all numbers between two different numbers, e.g. NumRange 5 10 is the type of all numbers between 5 and 10. I'd like to include doubles/floats, but a type for...

I'm at an odd place trying to prove an equation: 1 subgoals A : Type s : set A x : A s0 : s x x0 : A s1 : s x0 H : x0 = x ______________________________________(1/1) stv s x0 s1 = stv s x s0 What I...

I'm trying to write in Idris a function that create a Vect by passing the size of the Vect and a function taking the index in parameter. So far, I've this : import Data.Fin import Data.Vect generate: (n:Nat) -> (Nat -> a) ->Vect n a generate n f = generate'...

I wonder if I can have my cake and eat it too regarding KnownNats. Can I write code that uses Nats that may be both KnownNats and UnknownNats (SomeNats?). For example if I have a dependently typed vector Vec (n :: Nat) a, can I write code that works both...

I'm teaching myself about dependent types by learning Agda. Here's a type for binary trees balanced by their size. open import Data.Nat open import Data.Nat.Properties.Simple data T (A : Set) : ℕ -> Set where empty : T A 0 leaf : A -> T A 1 bal : ∀...

I am using a standard type-encoding of natural numbers in Scala. For the purpose of this question, the following definition will do: sealed trait Nat sealed trait _0 extends Nat sealed trait Succ[N <: Nat] extends Nat I can use the compiler to convert these Nat types into actual numbers,...

As an exercise in Coq, I'm trying to prove that the following function returns a pair of lists of equal length. Require Import List. Fixpoint split (A B:Set)(x:list (A*B)) : (list A)*(list B) := match x with |nil => (nil, nil) |cons (a,b) x1 => let (ta, tb) := split...