type-level-sets: Type-level sets and finite maps (with value-level counterparts)
This package provides type-level sets (no duplicates, sorted to provide a normal form) via Set
and type-level
finite maps via Map
, with value-level counterparts.
Described in the paper "Embedding effect systems in Haskell" by Dominic Orchard and Tomas Petricek http://www.cl.cam.ac.uk/~dao29/publ/haskell14-effects.pdf (Haskell Symposium, 2014). This version now uses Quicksort to normalise the representation.
Here is a brief example for finite maps:
import Data.Type.Map -- Specify how to combine duplicate key-value pairs for Int values type instance Combine Int Int = Int instance Combinable Int Int where combine x y = x + y foo :: Map '["x" :-> Int, "z" :-> Bool, "w" :-> Int] foo = Ext (Var :: (Var "x")) 2 $ Ext (Var :: (Var "z")) True $ Ext (Var :: (Var "w")) 5 $ Empty bar :: Map '["y" :-> Int, "w" :-> Int] bar = Ext (Var :: (Var "y")) 3 $ Ext (Var :: (Var "w")) 1 $ Empty -- foobar :: Map '["w" :-> Int, "x" :-> Int, "y" :-> Int, "z" :-> Bool] foobar = foo `union` bar
The Map
type for foobar
here shows the normalised form (sorted with no duplicates).
The type signatures is commented out as it can be infered. Running the example we get:
>>> foobar {w :-> 6, x :-> 2, y :-> 3, z :-> True}
Thus, we see that the values for "w" are added together. For sets, here is an example:
import GHC.TypeLits import Data.Type.Set type instance Cmp (Natural n) (Natural m) = CmpNat n m data Natural (a :: Nat) where Z :: Natural 0 S :: Natural n -> Natural (n + 1) -- foo :: Set '[Natural 0, Natural 1, Natural 3] foo = asSet $ Ext (S Z) (Ext (S (S (S Z))) (Ext Z Empty)) -- bar :: Set '[Natural 1, Natural 2] bar = asSet $ Ext (S (S Z)) (Ext (S Z) (Ext (S Z) Empty)) -- foobar :: Set '[Natural 0, Natural 1, Natural 2, Natural 3] foobar = foo `union` bar
Note the types here are all inferred.
Downloads
- type-level-sets-0.8.9.0.tar.gz [browse] (Cabal source package)
- Package description (revised from the package)
Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.
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Candidates
Versions [RSS] | 0.5, 0.6, 0.6.1, 0.7, 0.8.0.0, 0.8.5.0, 0.8.6.0, 0.8.7.0, 0.8.9.0 |
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Dependencies | base (<4.16), ghc-prim [details] |
License | BSD-3-Clause |
Copyright | 2013-18 University of Kent |
Author | Dominic Orchard |
Maintainer | Dominic Orchard |
Revised | Revision 2 made by sjakobi at 2022-10-14T18:02:45Z |
Category | Type System, Data Structures |
Source repo | head: git clone https://github.com/dorchard/type-level-sets |
Uploaded | by DominicOrchard at 2018-11-29T11:44:02Z |
Distributions | |
Reverse Dependencies | 5 direct, 0 indirect [details] |
Downloads | 6924 total (24 in the last 30 days) |
Rating | 2.0 (votes: 1) [estimated by Bayesian average] |
Your Rating | |
Status | Docs available [build log] Last success reported on 2018-11-29 [all 1 reports] |