data-kinds Questions
2
Solved
I'm confused about the error that I received at the end of the session below:
$ ghci
GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help
Ok, modules loaded: Main.
*Main> :set -XDataKi...
Dropsonde asked 5/11, 2015 at 20:56
1
I'm very puzzled by how Servant is able to achieve the magic that it does using typing. The example on the web site already puzzles me greatly:
type MyAPI = "date" :> Get '[JSON] Date
:<|&g...
Hoiden asked 31/10, 2015 at 20:6
3
Solved
The following example is a boiled-down version of my real-life problem. It seems to be in some way similar to Retrieving information from DataKinds constrained existential types, but I could not qu...
Interwork asked 4/9, 2015 at 23:54
1
Solved
How does one define new computation over types of kind GHC.TypeLits.Nat? I am hoping to be able to define a type family
type family WIDTH (n :: Nat) :: Nat
such that WIDTH 0 ~ 0 and WIDTH (n+1) ...
Rozella asked 16/6, 2015 at 11:44
2
Solved
Given an ADT like
data K = A | B Bool
the DataKinds extension allows us to lift it into kinds and types/type constructors
K :: BOX
'A :: K
'B :: 'Bool -> K
Is there a way to add a construc...
Mood asked 11/6, 2015 at 13:15
1
Solved
Disclaimer
GADTs & DataKinds are unexplored territory for me, so some of the limitations and capabilities of them are unknown to me.
The Question
So I'm writing an AST for a JavaScript code ...
Norinenorita asked 7/2, 2015 at 23:25
2
Solved
Let's say I have a Currency type:
data Currency = USD | EUR | YEN
and a Money type that stores an int, and is parameterized by a given Currency (Currency is promoted to a kind with the DataKinds...
Sousaphone asked 2/2, 2015 at 18:11
1
Solved
I've been playing with -XDataKinds recently, and would like to take a promoted structure build with type families and pull it back down to the value level. I believe this is possible because the co...
Heartfelt asked 19/1, 2015 at 17:15
0
I've been toying around with -XDataKinds recently, and was wondering why Foo below won't be automatically promoted:
{-# LANGUAGE
GADTs
, DataKinds
, KindSignatures #-}
import Data.HList
data ...
Unbonnet asked 17/12, 2014 at 15:0
0
I'm using the genifunctors package to generate a functor instance for a type whose definition involves type families.
The first module defines the data type itself:
{-# LANGUAGE TypeFamilies #-}
...
Minoru asked 26/9, 2014 at 13:24
1
Solved
So, I was playing around with DataKinds and TypeFamilies in Haskell and started to look at the Core GHC generated.
Here is a little TestCase to motivate my question:
{-# LANGUAGE GADTs #-}
{-# LA...
Balzer asked 19/9, 2014 at 12:42
2
Solved
I'm trying to derive a Typeable instance for tupled constraints. See the following code:
{-# LANGUAGE ConstraintKinds, GADTs #-}
{-# LANGUAGE DataKinds, PolyKinds, AutoDeriveTypeable #-}
{-# LANG...
Chicanery asked 17/9, 2014 at 14:19
1
Solved
I found an interesting situation, when using data kinds with type families.
The compiler's error message is No instance for (C (ID ())) arising from a use of W. It suggests that a type family appl...
Praedial asked 16/9, 2014 at 16:32
2
Solved
With DataKinds, a definition like
data KFoo = TFoo
introduces the kind KFoo :: BOX and the type TFoo :: KFoo. Why can't I then go on to define
data TFoo = CFoo
such that CFoo :: TFoo, TFoo ::...
Bosomed asked 26/6, 2014 at 20:27
1
Solved
If I have a type constrained by a finite DataKind
{-# LANGUAGE DataKinds #-}
data K = A | B
data Ty (a :: K) = Ty { ... }
and an existential type which forgets the exact choice of K in the typ...
Workhouse asked 24/6, 2014 at 13:25
2
Solved
I am trying to find an explanation of the DataKinds extension that will make sense to me having come from only having read Learn You a Haskell. Is there a standard source that will make sense to me...
Assignment asked 13/12, 2013 at 3:36
2
Solved
Why is it harder to build values with datakinds, while it's relatively easy to pattern match with them?
{-# LANGUAGE KindSignatures
, GADTs
, DataKinds
, Rank2Types
#-}
data Nat = Zero | Suc...
Farthermost asked 4/5, 2014 at 0:39
1
Solved
Here is the code where I'm having an issue:
{-# LANGUAGE GADTs, LANGUAGE DataKinds #-}
-- * Universe of Terms * --
type Id = String
data Term a where
Var :: Id -> Term a
Lam :: Id ->...
Jeannettajeannette asked 20/1, 2014 at 15:58
2
Solved
Could anyone explain or guess the motivation behind the limit on data type promotion discussed in section 7.9.2 of the GHC user guide?
The following restrictions apply to promotion:
We only...
Guessrope asked 18/1, 2014 at 16:21
2
Solved
I've been reading on vinyl recently, which uses weird "list of kinds" kinda types. After reading a bit on kinds and vinyl, I've gotten somewhat of an intuitive understanding of them, and I've been ...
Number asked 26/11, 2013 at 21:51
1
Solved
I want to implement the yin-yang puzzle in Haskell. Here is my attempt (unsucceful):
-- The data type in use is recursive, so we must have a newtype defined
newtype Cl m = Cl { goOn :: MonadCont m...
Toby asked 14/11, 2013 at 3:23
1
Solved
I'm having problems getting GHC to infer a type in a place where it should be obvious. Below is a complete snippet demonstrating the problem.
{-# LANGUAGE DataKinds, ScopedTypeVariables, KindSigna...
Joselow asked 10/9, 2013 at 3:14
1
Solved
I'm trying to implement a kind of zipper for length-indexed lists which would return each item of the list paired with a list where that element is removed. E.g. for ordinary lists:
zipper :: [a] ...
Dorene asked 6/7, 2013 at 9:57
1
Solved
So let's say I wrote some type-level program in Haskell:
type family NAryFn (n::Nat) (dom::*) (cod::*) :: *
type instance NAryFn Ze dom cod = cod
type instance NAryFn (Su n) dom cod = dom -> NA...
Rib asked 8/3, 2013 at 1:30
1
I'm trying to get a good grasp on Kinds, Types & Terms(or Values, not sure which is correct) and the GHC extensions for manipulating them. I understand that we can use TypeFamilies to write fun...
Directrix asked 19/2, 2013 at 2:50
© 2022 - 2024 — McMap. All rights reserved.