diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown --- a/CHANGELOG.markdown +++ b/CHANGELOG.markdown @@ -1,3 +1,117 @@ +0.14.4 [2026.01.26] +------------------- +* Depend on `ghc-bignum` instead of `integer-gmp` on recent versions GHC. + +0.14.3 [2026.01.10] +------------------- +* Remove unused `ghc-prim` dependency. + +0.14.2 [2024.05.12] +------------------- +* Re-export `Log2` from `Data.Constraint.Nat`. +* Add `log2Nat` and `log2Pow` to `Data.Constraint.Nat`. + +0.14.1 [2024.04.29] +------------------- +* Remove an unused dependency on the `type-equality` library. + +0.14 [2023.10.11] +----------------- +* Drop support for GHCs older than 8.6. +* The `forall` function in `Data.Constraint.Forall` has been renamed to + `forall_`, since a future version of GHC will make the use of `forall` as + an identifier an error. +* Implement `Data.Constraint.Forall` using `QuantifiedConstraints`. +* Remove `Lifting` instances for `ErrorT` and `ListT`, which were removed + in `transformers-0.6.*`. +* Add a `c => Boring (Dict c)` instance. +* Add the `Data.Constraint.Char` module, which contains utilities for working + with `KnownChar` constraints. This module is only available on GHC 9.2 or + later. +* Add `unsafeAxiom` to `Data.Constraint.Unsafe`. +* Add `unsafeSChar`, `unsafeSNat`, and `unsafeSSymbol` to + `Data.Constraint.Unsafe` when building with `base-4.18` (GHC 9.6) or later. + +0.13.4 [2022.05.19] +------------------- +* Correct the CPP introduced in `constraints-0.13.3` such that it works when + building with `mtl-2.3.*` or later combined with `transformers < 0.6`. + +0.13.3 [2022.01.31] +------------------- +* Allow building with `transformers-0.6.*` and `mtl-2.3.*`. + +0.13.2 [2021.11.10] +------------------- +* Allow building on GHC HEAD. + +0.13.1 [2021.10.31] +------------------- +* Allow building with GHC 9.2. + +0.13 [2021.02.17] +----------------- +* `Data.Constraint.Symbol` now reexports the `GHC.TypeLits.AppendSymbol` type + family from recent versions of `base` (or, on old versions of `base`, it + defines a backwards-compatibile version of `AppendSymbol`). The existing + `(++)` type family for `Data.Constraint.Symbol` is now a synonym for + `AppendSymbol`. + + This is technically a breaking change, as `(++)` was previously defined like + so: + + ```hs + type family (++) :: Symbol -> Symbol -> Symbol + ``` + + This meant that `(++)` could be partially applied. However, for compatibility + with the way that `AppendSymbol` is defined, `(++)` is now defined like so: + + ```hs + type m ++ n = AppendSymbol m n + ``` + + As a result, `(++)` can no longer be partially applied. +* Make the `(++)` type family in `Data.Constraint.Symbol` be `infixr 5`. +* Add `implied :: (a => b) -> (a :- b)` to `Data.Constraint`, which converts + a quantified constraint into an entailment. This is only available when + compiled with GHC 8.6 or later. + +0.12 [2020.02.03] +----------------- +* Relax the type signature for `divideTimes`: + + ```diff + -dividesTimes :: (Divides a b, Divides a c) :- Divides a (b * c) + +dividesTimes :: Divides a b :- Divides a (b * c) + ``` + +* Simplify the type signature of `dividesDef`: + + ```diff + -dividesDef :: forall a b. Divides a b :- ((a * Div b a) ~ b) + +dividesDef :: forall a b. Divides a b :- (Mod b a ~ 0) + ``` + + The original type of `diviesDef` can be (partially) recovered by defining + it in terms of the new `dividesDef`: + + ```hs + dividesDef' :: forall a b. (1 <= a, Divides a b) :- ((a * Div b a) ~ b) + dividesDef' = Sub $ case (dividesDef @a @b, euclideanNat @a @b) of + (Sub Dict, Sub Dict) -> Dict + ``` + +0.11.2 [2019.09.06] +------------------- +* Depend on the `type-equality` compatibility library so that `(:~~:)` may be + used when compiling this library with GHC 8.0. This avoids having to redefine + `(:~~:)` directly in the internals of `constraints` itself. + +0.11.1 [2019.08.27] +------------------- +* Make `Data.Constraint.Deferrable.UnsatisfiedConstraint` a newtype. + 0.11 [2019.05.10] ----------------- * Introduce a `HasDict` type class for types that witness evidence of diff --git a/README.markdown b/README.markdown --- a/README.markdown +++ b/README.markdown @@ -1,7 +1,7 @@ constraints =========== -[![Hackage](https://img.shields.io/hackage/v/constraints.svg)](https://hackage.haskell.org/package/constraints) [![Build Status](https://secure.travis-ci.org/ekmett/constraints.png?branch=master)](http://travis-ci.org/ekmett/constraints) +[![Hackage](https://img.shields.io/hackage/v/constraints.svg)](https://hackage.haskell.org/package/constraints) [![Build Status](https://github.com/ekmett/constraints/workflows/Haskell-CI/badge.svg)](https://github.com/ekmett/constraints/actions?query=workflow%3AHaskell-CI) This package provides data types and classes for manipulating the 'ConstraintKinds' exposed by GHC in 7.4. diff --git a/constraints.cabal b/constraints.cabal --- a/constraints.cabal +++ b/constraints.cabal @@ -1,15 +1,15 @@ +cabal-version: 2.4 name: constraints category: Constraints -version: 0.11 -license: BSD2 -cabal-version: >= 1.10 +version: 0.14.4 +license: BSD-2-Clause license-file: LICENSE author: Edward A. Kmett maintainer: Edward A. Kmett stability: experimental homepage: http://github.com/ekmett/constraints/ bug-reports: http://github.com/ekmett/constraints/issues -copyright: Copyright (C) 2011-2015 Edward A. Kmett +copyright: Copyright (C) 2011-2021 Edward A. Kmett synopsis: Constraint manipulation description: GHC 7.4 gave us the ability to talk about @ConstraintKinds@. They stopped crashing the compiler in GHC 7.6. @@ -17,19 +17,26 @@ This package provides a vocabulary for working with them. build-type: Simple -tested-with: GHC == 7.8.4 - , GHC == 7.10.3 - , GHC == 8.0.2 - , GHC == 8.2.2 - , GHC == 8.4.4 - , GHC == 8.6.5 - , GHC == 8.8.1 + +tested-with: + GHC == 9.14.1 + GHC == 9.12.2 + GHC == 9.10.3 + GHC == 9.8.4 + GHC == 9.6.7 + GHC == 9.4.8 + GHC == 9.2.8 + GHC == 9.0.2 + GHC == 8.10.7 + GHC == 8.8.4 + GHC == 8.6.5 + extra-source-files: README.markdown , CHANGELOG.markdown source-repository head type: git - location: git://github.com/ekmett/constraints.git + location: https://github.com/ekmett/constraints.git library hs-source-dirs: src @@ -48,29 +55,34 @@ GADTs build-depends: - base >= 4.7 && < 5, - binary >= 0.7.1 && < 0.9, - deepseq >= 1.3 && < 1.5, - ghc-prim, - hashable >= 1.2 && < 1.4, - mtl >= 2.1.2 && < 2.3, - semigroups >= 0.17 && < 0.20, - transformers >= 0.3.0.0 && < 0.6, - transformers-compat >= 0.5 && < 1 + , base >= 4.12 && < 5 + , binary >= 0.7.1 && < 0.9 + , boring >= 0.2 && < 0.3 + , deepseq >= 1.3 && < 1.6 + , hashable >= 1.2 && < 1.6 + , mtl >= 2.2 && < 2.4 + , transformers >= 0.5 && < 0.7 + if impl(ghc >= 9.15) + build-depends: + ghc-bignum + elif impl(ghc < 9.0) + build-depends: + integer-gmp exposed-modules: Data.Constraint Data.Constraint.Deferrable Data.Constraint.Forall Data.Constraint.Lifting + Data.Constraint.Nat + Data.Constraint.Symbol Data.Constraint.Unsafe - if impl(ghc >= 8) + if impl(ghc >= 9.2) exposed-modules: - Data.Constraint.Nat - Data.Constraint.Symbol + Data.Constraint.Char - ghc-options: -Wall + ghc-options: -Wall -Wno-star-is-type test-suite spec type: exitcode-stdio-1.0 @@ -78,9 +90,10 @@ hs-source-dirs: tests main-is: Spec.hs other-modules: GH55Spec + GH117Spec ghc-options: -Wall -threaded -rtsopts build-tool-depends: hspec-discover:hspec-discover >= 2 build-depends: - base >= 4.7 && < 5, - constraints, - hspec >= 2 + , base + , constraints + , hspec >= 2 diff --git a/src/Data/Constraint.hs b/src/Data/Constraint.hs --- a/src/Data/Constraint.hs +++ b/src/Data/Constraint.hs @@ -1,38 +1,28 @@ -{-# LANGUAGE FunctionalDependencies #-} -{-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE AllowAmbiguousTypes #-} -{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE DeriveDataTypeable #-} -{-# LANGUAGE StandaloneDeriving #-} -{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE DerivingStrategies #-} {-# LANGUAGE FlexibleContexts #-} -{-# LANGUAGE ConstraintKinds #-} -{-# LANGUAGE RoleAnnotations #-} -{-# LANGUAGE EmptyDataDecls #-} -{-# LANGUAGE KindSignatures #-} -{-# LANGUAGE TypeOperators #-} -{-# LANGUAGE UnicodeSyntax #-} -{-# LANGUAGE TypeFamilies #-} -{-# LANGUAGE Trustworthy #-} -{-# LANGUAGE Rank2Types #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE GADTs #-} -{-# LANGUAGE CPP #-} -#if __GLASGOW_HASKELL__ >= 706 {-# LANGUAGE PolyKinds #-} -#endif -#if __GLASGOW_HASKELL__ >= 800 -{-# LANGUAGE TypeInType #-} +{-# LANGUAGE QuantifiedConstraints #-} +{-# LANGUAGE Rank2Types #-} +{-# LANGUAGE RoleAnnotations #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneDeriving #-} +{-# LANGUAGE Trustworthy #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeOperators #-} +{-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE UndecidableSuperClasses #-} -#endif -#if __GLASGOW_HASKELL__ >= 708 && __GLASGOW_HASKELL__ < 710 -{-# LANGUAGE NullaryTypeClasses #-} -#endif ------------------------------------------------------------------------------ +{-# LANGUAGE UnicodeSyntax #-} + -- | --- Module : Data.Constraint -- Copyright : (C) 2011-2015 Edward Kmett, -- License : BSD-style (see the file LICENSE) --- -- Maintainer : Edward Kmett -- Stability : experimental -- Portability : non-portable @@ -54,7 +44,7 @@ -- -- With @ConstraintKinds@ we can put into code a lot of tools for manipulating -- these new types without such awkward workarounds. ----------------------------------------------------------------------------- + module Data.Constraint ( -- * The Kind of Constraints @@ -67,10 +57,13 @@ -- * Entailment , (:-)(Sub) , type (⊢) + , type (|-) + , type (&) , weaken1, weaken2, contract , strengthen1, strengthen2 , (&&&), (***) , trans, refl + , implied , Bottom(no) , top, bottom -- * Dict is fully faithful @@ -85,30 +78,19 @@ import Control.DeepSeq import Control.Monad import Data.Complex -#if __GLASGOW_HASKELL__ >= 800 && __GLASGOW_HASKELL__ < 806 -import Data.Kind -#endif import Data.Ratio -#if !MIN_VERSION_base(4,11,0) -import Data.Semigroup -#endif import Data.Data hiding (TypeRep) import qualified GHC.Exts as Exts (Any) import GHC.Exts (Constraint) import Data.Bits (Bits) import Data.Functor.Identity (Identity) -#if MIN_VERSION_base(4,8,0) import Numeric.Natural (Natural) -#endif -#if !MIN_VERSION_base(4,8,0) -import Data.Word (Word) -#endif import Data.Coerce (Coercible) import Data.Type.Coercion(Coercion(..)) -#if MIN_VERSION_base(4,10,0) import Data.Type.Equality (type (~~)) +import qualified Data.Type.Equality as Hetero import Type.Reflection (TypeRep, typeRepKind, withTypeable) -#endif +import Data.Boring (Boring (..)) -- | Values of type @'Dict' p@ capture a dictionary for a constraint of type @p@. -- @@ -121,16 +103,23 @@ -- captures a dictionary that proves we have an: -- -- @ --- instance 'Eq' 'Int +-- instance 'Eq' 'Int' -- @ -- -- Pattern matching on the 'Dict' constructor will bring this instance into scope. -- data Dict :: Constraint -> * where Dict :: a => Dict a - deriving Typeable +deriving stock instance (Typeable p, p) => Data (Dict p) +deriving stock instance Eq (Dict a) +deriving stock instance Ord (Dict a) +deriving stock instance Show (Dict a) +instance c => Boring (Dict c) where + boring = Dict + +{- instance (Typeable p, p) => Data (Dict p) where gfoldl _ z Dict = z Dict toConstr _ = dictConstr @@ -144,10 +133,8 @@ dictDataType :: DataType dictDataType = mkDataType "Data.Constraint.Dict" [dictConstr] +-} -deriving instance Eq (Dict a) -deriving instance Ord (Dict a) -deriving instance Show (Dict a) instance NFData (Dict c) where rnf Dict = () @@ -170,13 +157,11 @@ instance HasDict (a ~ b) (a :~: b) where evidence Refl = Dict -#if MIN_VERSION_base(4,10,0) -instance HasDict (a ~~ b) (a :~~: b) where - evidence HRefl = Dict +instance HasDict (a ~~ b) (a Hetero.:~~: b) where + evidence Hetero.HRefl = Dict instance HasDict (Typeable k, Typeable a) (TypeRep (a :: k)) where evidence tr = withTypeable tr $ withTypeable (typeRepKind tr) Dict -#endif -- | From a 'Dict', takes a value in an environment where the instance -- witnessed by the 'Dict' is in scope, and evaluates it. @@ -203,6 +188,7 @@ infixr 9 :- infixr 9 ⊢ +-- | Type entailment, as written with a single character. type (⊢) = (:-) -- | This is the type of entailment. @@ -260,28 +246,23 @@ -- library is sensible and can't break any assumptions on the behalf of -- library authors. newtype a :- b = Sub (a => Dict b) - deriving Typeable type role (:-) nominal nominal --- TODO: _proper_ Data for @(p ':-' q)@ requires @(:-)@ to be cartesian _closed_. --- --- This is admissable, but not present by default - --- constraint should be instance (Typeable p, Typeable q, p |- q) => Data (p :- q) -instance (Typeable p, Typeable q, p, q) => Data (p :- q) where - gfoldl _ z (Sub Dict) = z (Sub Dict) - toConstr _ = subConstr +instance (Typeable p, Typeable q, p => q) => Data (p :- q) where + gfoldl _ z d = z d gunfold _ z c = case constrIndex c of - 1 -> z (Sub Dict) - _ -> error "gunfold" - dataTypeOf _ = subDataType - -subConstr :: Constr -subConstr = mkConstr dictDataType "Sub" [] Prefix + 1 -> z (Sub Dict) + _ -> error "Data.Data.Data: Data.Constraint.:- constructor out of bounds" + toConstr _ = subCon + dataTypeOf _ = subTy -subDataType :: DataType -subDataType = mkDataType "Data.Constraint.:-" [subConstr] +subCon :: Constr +subCon = mkConstr subTy "Sub Dict" [] Prefix +{-# noinline subCon #-} +subTy :: DataType +subTy = mkDataType "Data.Constraint.:-" [subCon] +{-# noinline subTy #-} -- | Possible since GHC 7.8, when 'Category' was made polykinded. instance Category (:-) where @@ -319,10 +300,46 @@ refl = Sub Dict -------------------------------------------------------------------------------- +-- QuantifiedConstraints +-------------------------------------------------------------------------------- + +-- | Convert a quantified constraint into an entailment. +implied :: forall a b. (a => b) => a :- b +implied = Sub (Dict :: Dict b) + +-- | The internal hom for the category of constraints. +-- +-- This version can be passed around inside Dict, whereas (a => b) is impredicative +-- +-- @ +-- foo :: Dict (Ord a => Eq a) +-- foo = Dict +-- @ +-- +-- fails to typecheck due to the lack of impredicative polymorphism, but +-- +-- @ +-- foo :: Dict (Ord a |- Eq a) +-- foo = Dict +-- @ +-- +-- typechecks just fine. + +class (p => q) => p |- q +instance (p => q) => p |- q + + +-------------------------------------------------------------------------------- -- (,) is a Bifunctor -------------------------------------------------------------------------------- -- | due to the hack for the kind of @(,)@ in the current version of GHC we can't actually +-- make instances for @(,) :: Constraint -> Constraint -> Constraint@, but we can define +-- an equivalent type, that converts back and forth to @(,)@, and lets you hang instances. +class (p,q) => p & q +instance (p,q) => p & q + +-- | due to the hack for the kind of @(,)@ in the current version of GHC we can't actually -- make instances for @(,) :: Constraint -> Constraint -> Constraint@, but @(,)@ is a -- bifunctor on the category of constraints. This lets us map over both sides. (***) :: (a :- b) -> (c :- d) -> (a, c) :- (b, d) @@ -474,10 +491,8 @@ instance () :=> Eq (a :- b) where ins = Sub Dict instance () :=> Eq Word where ins = Sub Dict instance Eq a :=> Eq (Identity a) where ins = Sub Dict -#if MIN_VERSION_base(4,8,0) instance Eq a :=> Eq (Const a b) where ins = Sub Dict instance () :=> Eq Natural where ins = Sub Dict -#endif -- Ord instance Class (Eq a) (Ord a) where cls = Sub Dict @@ -497,10 +512,8 @@ instance () :=> Ord (a :- b) where ins = Sub Dict instance () :=> Ord Word where ins = Sub Dict instance Ord a :=> Ord (Identity a) where ins = Sub Dict -#if MIN_VERSION_base(4,8,0) instance Ord a :=> Ord (Const a b) where ins = Sub Dict instance () :=> Ord Natural where ins = Sub Dict -#endif -- Show instance Class () (Show a) where cls = Sub Dict @@ -519,10 +532,8 @@ instance () :=> Show (a :- b) where ins = Sub Dict instance () :=> Show Word where ins = Sub Dict instance Show a :=> Show (Identity a) where ins = Sub Dict -#if MIN_VERSION_base(4,8,0) instance Show a :=> Show (Const a b) where ins = Sub Dict instance () :=> Show Natural where ins = Sub Dict -#endif -- Read instance Class () (Read a) where cls = Sub Dict @@ -539,10 +550,8 @@ instance (Integral a, Read a) :=> Read (Ratio a) where ins = Sub Dict instance () :=> Read Word where ins = Sub Dict instance Read a :=> Read (Identity a) where ins = Sub Dict -#if MIN_VERSION_base(4,8,0) instance Read a :=> Read (Const a b) where ins = Sub Dict instance () :=> Read Natural where ins = Sub Dict -#endif -- Enum instance Class () (Enum a) where cls = Sub Dict @@ -556,13 +565,9 @@ instance () :=> Enum Double where ins = Sub Dict instance Integral a :=> Enum (Ratio a) where ins = Sub Dict instance () :=> Enum Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Enum a :=> Enum (Identity a) where ins = Sub Dict instance Enum a :=> Enum (Const a b) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,8,0) instance () :=> Enum Natural where ins = Sub Dict -#endif -- Bounded instance Class () (Bounded a) where cls = Sub Dict @@ -573,10 +578,8 @@ instance () :=> Bounded Char where ins = Sub Dict instance (Bounded a, Bounded b) :=> Bounded (a,b) where ins = Sub Dict instance () :=> Bounded Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Bounded a :=> Bounded (Identity a) where ins = Sub Dict instance Bounded a :=> Bounded (Const a b) where ins = Sub Dict -#endif -- Num instance Class () (Num a) where cls = Sub Dict @@ -587,13 +590,9 @@ instance RealFloat a :=> Num (Complex a) where ins = Sub Dict instance Integral a :=> Num (Ratio a) where ins = Sub Dict instance () :=> Num Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Num a :=> Num (Identity a) where ins = Sub Dict instance Num a :=> Num (Const a b) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,8,0) instance () :=> Num Natural where ins = Sub Dict -#endif -- Real instance Class (Num a, Ord a) (Real a) where cls = Sub Dict @@ -603,26 +602,18 @@ instance () :=> Real Double where ins = Sub Dict instance Integral a :=> Real (Ratio a) where ins = Sub Dict instance () :=> Real Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Real a :=> Real (Identity a) where ins = Sub Dict instance Real a :=> Real (Const a b) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,8,0) instance () :=> Real Natural where ins = Sub Dict -#endif -- Integral instance Class (Real a, Enum a) (Integral a) where cls = Sub Dict instance () :=> Integral Int where ins = Sub Dict instance () :=> Integral Integer where ins = Sub Dict instance () :=> Integral Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Integral a :=> Integral (Identity a) where ins = Sub Dict instance Integral a :=> Integral (Const a b) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,8,0) instance () :=> Integral Natural where ins = Sub Dict -#endif -- Bits instance Class (Eq a) (Bits a) where cls = Sub Dict @@ -630,13 +621,9 @@ instance () :=> Bits Int where ins = Sub Dict instance () :=> Bits Integer where ins = Sub Dict instance () :=> Bits Word where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Bits a :=> Bits (Identity a) where ins = Sub Dict instance Bits a :=> Bits (Const a b) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,8,0) instance () :=> Bits Natural where ins = Sub Dict -#endif -- Fractional instance Class (Num a) (Fractional a) where cls = Sub Dict @@ -644,39 +631,31 @@ instance () :=> Fractional Double where ins = Sub Dict instance RealFloat a :=> Fractional (Complex a) where ins = Sub Dict instance Integral a :=> Fractional (Ratio a) where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Fractional a :=> Fractional (Identity a) where ins = Sub Dict instance Fractional a :=> Fractional (Const a b) where ins = Sub Dict -#endif -- Floating instance Class (Fractional a) (Floating a) where cls = Sub Dict instance () :=> Floating Float where ins = Sub Dict instance () :=> Floating Double where ins = Sub Dict instance RealFloat a :=> Floating (Complex a) where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Floating a :=> Floating (Identity a) where ins = Sub Dict instance Floating a :=> Floating (Const a b) where ins = Sub Dict -#endif -- RealFrac instance Class (Real a, Fractional a) (RealFrac a) where cls = Sub Dict instance () :=> RealFrac Float where ins = Sub Dict instance () :=> RealFrac Double where ins = Sub Dict instance Integral a :=> RealFrac (Ratio a) where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance RealFrac a :=> RealFrac (Identity a) where ins = Sub Dict instance RealFrac a :=> RealFrac (Const a b) where ins = Sub Dict -#endif -- RealFloat instance Class (RealFrac a, Floating a) (RealFloat a) where cls = Sub Dict instance () :=> RealFloat Float where ins = Sub Dict instance () :=> RealFloat Double where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance RealFloat a :=> RealFloat (Identity a) where ins = Sub Dict instance RealFloat a :=> RealFloat (Const a b) where ins = Sub Dict -#endif -- Semigroup instance Class () (Semigroup a) where cls = Sub Dict @@ -686,29 +665,19 @@ instance Semigroup a :=> Semigroup (Maybe a) where ins = Sub Dict instance (Semigroup a, Semigroup b) :=> Semigroup (a, b) where ins = Sub Dict instance Semigroup a :=> Semigroup (Const a b) where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Semigroup a :=> Semigroup (Identity a) where ins = Sub Dict -#endif -#if MIN_VERSION_base(4,10,0) instance Semigroup a :=> Semigroup (IO a) where ins = Sub Dict -#endif -- Monoid -#if MIN_VERSION_base(4,11,0) instance Class (Semigroup a) (Monoid a) where cls = Sub Dict -#else -instance Class () (Monoid a) where cls = Sub Dict -#endif instance () :=> Monoid () where ins = Sub Dict instance () :=> Monoid Ordering where ins = Sub Dict instance () :=> Monoid [a] where ins = Sub Dict instance Monoid a :=> Monoid (Maybe a) where ins = Sub Dict instance (Monoid a, Monoid b) :=> Monoid (a, b) where ins = Sub Dict instance Monoid a :=> Monoid (Const a b) where ins = Sub Dict -#if MIN_VERSION_base(4,9,0) instance Monoid a :=> Monoid (Identity a) where ins = Sub Dict instance Monoid a :=> Monoid (IO a) where ins = Sub Dict -#endif -- Functor instance Class () (Functor f) where cls = Sub Dict @@ -740,11 +709,7 @@ instance MonadPlus m :=> Alternative (WrappedMonad m) where ins = Sub Dict -- Monad -#if MIN_VERSION_base(4,8,0) instance Class (Applicative f) (Monad f) where cls = Sub Dict -#else -instance Class () (Monad f) where cls = Sub Dict -#endif instance () :=> Monad [] where ins = Sub Dict instance () :=> Monad ((->) a) where ins = Sub Dict instance () :=> Monad (Either a) where ins = Sub Dict @@ -752,11 +717,7 @@ instance () :=> Monad Identity where ins = Sub Dict -- MonadPlus -#if MIN_VERSION_base(4,8,0) instance Class (Monad f, Alternative f) (MonadPlus f) where cls = Sub Dict -#else -instance Class (Monad f) (MonadPlus f) where cls = Sub Dict -#endif instance () :=> MonadPlus [] where ins = Sub Dict instance () :=> MonadPlus Maybe where ins = Sub Dict @@ -783,7 +744,4 @@ instance a :=> Monoid (Dict a) where ins = Sub Dict instance a => Monoid (Dict a) where -#if !(MIN_VERSION_base(4,11,0)) - mappend = (<>) -#endif mempty = Dict diff --git a/src/Data/Constraint/Char.hs b/src/Data/Constraint/Char.hs new file mode 100644 --- /dev/null +++ b/src/Data/Constraint/Char.hs @@ -0,0 +1,60 @@ +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE AllowAmbiguousTypes #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE TypeOperators #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE RankNTypes #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE PolyKinds #-} +{-# LANGUAGE CPP #-} +-- | Utilities for working with 'KnownChar' constraints. +-- +-- This module is only available on GHC 9.2 or later. +module Data.Constraint.Char + ( CharToNat + , NatToChar + , charToNat + , natToChar + ) where + +import Data.Char +import Data.Constraint +import Data.Proxy +import GHC.TypeLits +#if MIN_VERSION_base(4,18,0) +import Data.Constraint.Unsafe +import qualified GHC.TypeNats as TN +#else +import Unsafe.Coerce +#endif + +-- implementation details + +#if !MIN_VERSION_base(4,18,0) +newtype Magic c = Magic (KnownChar c => Dict (KnownChar c)) +#endif + +magicCN :: forall c n. (Char -> Int) -> KnownChar c :- KnownNat n +#if MIN_VERSION_base(4,18,0) +magicCN f = Sub $ TN.withKnownNat (unsafeSNat @n (fromIntegral (f (charVal (Proxy @c))))) Dict +#else +magicCN f = Sub $ unsafeCoerce (Magic Dict) (fromIntegral @Int @Natural (f (charVal (Proxy @c)))) +#endif + +magicNC :: forall n c. (Int -> Char) -> KnownNat n :- KnownChar c +#if MIN_VERSION_base(4,18,0) +magicNC f = Sub $ withKnownChar (unsafeSChar @c (f (fromIntegral (natVal (Proxy @n))))) Dict +#else +magicNC f = Sub $ unsafeCoerce (Magic Dict) (f (fromIntegral (natVal (Proxy @n)))) +#endif + +-- operations + +charToNat :: forall c. KnownChar c :- KnownNat (CharToNat c) +charToNat = magicCN ord + +-- NB: 0x10FFFF the maximum value for a Unicode code point. Calling `chr` on +-- anything greater will throw an exception. +natToChar :: forall n. (n <= 0x10FFFF, KnownNat n) :- KnownChar (NatToChar n) +natToChar = Sub $ case magicNC @n @(NatToChar n) chr of Sub r -> r diff --git a/src/Data/Constraint/Deferrable.hs b/src/Data/Constraint/Deferrable.hs --- a/src/Data/Constraint/Deferrable.hs +++ b/src/Data/Constraint/Deferrable.hs @@ -1,42 +1,27 @@ -{-# LANGUAGE CPP #-} -{-# LANGUAGE TypeOperators #-} -{-# LANGUAGE GADTs #-} +{-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE ConstraintKinds #-} -{-# LANGUAGE KindSignatures #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE PolyKinds #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} -{-# LANGUAGE DeriveDataTypeable #-} -{-# LANGUAGE PolyKinds #-} - -#if __GLASGOW_HASKELL__ >= 800 {-# LANGUAGE TypeApplications #-} -{-# LANGUAGE AllowAmbiguousTypes #-} -{-# LANGUAGE TypeInType #-} -#endif +{-# LANGUAGE TypeOperators #-} ------------------------------------------------------------------------------ -- | --- Module : Data.Constraint.Deferrable --- Copyright : (C) 2015-2016 Edward Kmett +-- Copyright : (C) 2015-2021 Edward Kmett -- License : BSD-style (see the file LICENSE) --- -- Maintainer : Edward Kmett -- Stability : experimental -- Portability : non-portable -- -- The idea for this trick comes from Dimitrios Vytiniotis. ------------------------------------------------------------------------------ module Data.Constraint.Deferrable ( UnsatisfiedConstraint(..) , Deferrable(..) , defer , deferred -#if __GLASGOW_HASKELL__ >= 800 - , defer_ - , deferEither_ , (:~~:)(HRefl) -#endif , (:~:)(Refl) ) where @@ -47,90 +32,51 @@ import Data.Typeable (Typeable, cast, typeRep) import Data.Type.Equality ((:~:)(Refl)) -#if __GLASGOW_HASKELL__ >= 800 -import GHC.Types (type (~~)) -#endif - -#if __GLASGOW_HASKELL__ >= 801 -import Data.Type.Equality ((:~~:)(HRefl)) -#endif +import Data.Type.Equality (type (~~), (:~~:)(HRefl)) -data UnsatisfiedConstraint = UnsatisfiedConstraint String - deriving (Typeable, Show) +newtype UnsatisfiedConstraint = UnsatisfiedConstraint String + deriving Show instance Exception UnsatisfiedConstraint -- | Allow an attempt at resolution of a constraint at a later time class Deferrable p where -- | Resolve a 'Deferrable' constraint with observable failure. - deferEither :: proxy p -> (p => r) -> Either String r - --- | Defer a constraint for later resolution in a context where we want to upgrade failure into an error -defer :: forall p r proxy. Deferrable p => proxy p -> (p => r) -> r -defer _ r = either (throw . UnsatisfiedConstraint) id $ deferEither (Proxy :: Proxy p) r + deferEither :: (p => r) -> Either String r deferred :: forall p. Deferrable p :- p -deferred = Sub $ defer (Proxy :: Proxy p) Dict - -#if __GLASGOW_HASKELL__ >= 800 --- | A version of 'defer' that uses visible type application in place of a 'Proxy'. --- --- Only available on GHC 8.0 or later. -defer_ :: forall p r. Deferrable p => (p => r) -> r -defer_ r = defer @p Proxy r - --- | A version of 'deferEither' that uses visible type application in place of a 'Proxy'. --- --- Only available on GHC 8.0 or later. -deferEither_ :: forall p r. Deferrable p => (p => r) -> Either String r -deferEither_ r = deferEither @p Proxy r -#endif +deferred = Sub $ defer @p Dict -#if __GLASGOW_HASKELL__ >= 800 && __GLASGOW_HASKELL__ < 801 --- | Kind heterogeneous propositional equality. Like '(:~:)', @a :~~: b@ is --- inhabited by a terminating value if and only if @a@ is the same type as @b@. --- --- Only available on GHC 8.0 or later. -data (a :: i) :~~: (b :: j) where - HRefl :: a :~~: a - deriving Typeable -#endif +defer :: forall p r. Deferrable p => (p => r) -> r +defer r = either (throw . UnsatisfiedConstraint) id $ deferEither @p r -showTypeRep :: Typeable t => Proxy t -> String -showTypeRep = show . typeRep +showTypeRep :: forall t. Typeable t => String +showTypeRep = show $ typeRep (Proxy @t) instance Deferrable () where - deferEither _ r = Right r + deferEither r = Right r -- | Deferrable homogeneous equality constraints. -- -- Note that due to a GHC bug (https://ghc.haskell.org/trac/ghc/ticket/10343), -- using this instance on GHC 7.10 will only work with @*@-kinded types. -#if __GLASGOW_HASKELL__ >= 800 instance (Typeable k, Typeable (a :: k), Typeable b) => Deferrable (a ~ b) where -#elif __GLASGOW_HASKELL__ == 710 -instance (Typeable a, Typeable b) => Deferrable ((a :: *) ~ (b :: *)) where -#else -instance (Typeable a, Typeable b) => Deferrable (a ~ b) where -#endif - deferEither _ r = case cast (Refl :: a :~: a) :: Maybe (a :~: b) of + deferEither r = case cast (Refl :: a :~: a) :: Maybe (a :~: b) of Just Refl -> Right r Nothing -> Left $ - "deferred type equality: type mismatch between `" ++ showTypeRep (Proxy :: Proxy a) ++ "’ and `" ++ showTypeRep (Proxy :: Proxy b) ++ "'" + "deferred type equality: type mismatch between `" ++ showTypeRep @a ++ "’ and `" ++ showTypeRep @b ++ "'" -#if __GLASGOW_HASKELL__ >= 800 -- | Deferrable heterogenous equality constraints. -- -- Only available on GHC 8.0 or later. instance (Typeable i, Typeable j, Typeable (a :: i), Typeable (b :: j)) => Deferrable (a ~~ b) where - deferEither _ r = case cast (HRefl :: a :~~: a) :: Maybe (a :~~: b) of + deferEither r = case cast (HRefl :: a :~~: a) :: Maybe (a :~~: b) of Just HRefl -> Right r Nothing -> Left $ - "deferred type equality: type mismatch between `" ++ showTypeRep (Proxy :: Proxy a) ++ "’ and `" ++ showTypeRep (Proxy :: Proxy b) ++ "'" -#endif + "deferred type equality: type mismatch between `" ++ showTypeRep @a ++ "’ and `" ++ showTypeRep @b ++ "'" instance (Deferrable a, Deferrable b) => Deferrable (a, b) where - deferEither _ r = join $ deferEither (Proxy :: Proxy a) $ deferEither (Proxy :: Proxy b) r + deferEither r = join $ deferEither @a $ deferEither @b r instance (Deferrable a, Deferrable b, Deferrable c) => Deferrable (a, b, c) where - deferEither _ r = join $ deferEither (Proxy :: Proxy a) $ join $ deferEither (Proxy :: Proxy b) $ deferEither (Proxy :: Proxy c) r + deferEither r = join $ deferEither @a $ join $ deferEither @b $ deferEither @c r diff --git a/src/Data/Constraint/Forall.hs b/src/Data/Constraint/Forall.hs --- a/src/Data/Constraint/Forall.hs +++ b/src/Data/Constraint/Forall.hs @@ -1,22 +1,21 @@ {-# LANGUAGE CPP #-} {-# LANGUAGE FunctionalDependencies #-} -{-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE TypeFamilies #-} -{-# LANGUAGE Trustworthy #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE PolyKinds #-} -#if __GLASGOW_HASKELL__ >= 800 {-# LANGUAGE UndecidableSuperClasses #-} -#endif ------------------------------------------------------------------------------ +{-# LANGUAGE Trustworthy #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE QuantifiedConstraints #-} +{-# LANGUAGE GADTs #-} + -- | --- Module : Data.Constraint.Forall --- Copyright : (C) 2011-2015 Edward Kmett, +-- Copyright : (C) 2011-2021 Edward Kmett, -- (C) 2015 Ørjan Johansen, -- (C) 2016 David Feuer -- License : BSD-style (see the file LICENSE) @@ -26,7 +25,6 @@ -- Portability : non-portable -- -- This module uses a trick to provide quantification over constraints. ----------------------------------------------------------------------------- module Data.Constraint.Forall ( Forall, inst @@ -34,95 +32,27 @@ , Forall1, inst1 , ForallT, instT , ForallV, InstV (instV) - , forall + , forall_ ) where import Data.Constraint import Unsafe.Coerce (unsafeCoerce) -#if __GLASGOW_HASKELL__ >= 806 -# define KVS(kvs) kvs -#else -# define KVS(kvs) -#endif - -{- The basic trick of this module is to use "skolem" types as test candidates - - for whether a class predicate holds, and if so assume that it holds for all - - types, unsafely coercing the typeclass dictionary. - - - - The particular technique used to implement 'Forall' appears to have been - - discovered first by Nicolas Frisby and is - - - - on his blog. - - - - However, his discovery did not directly affect the development of this - - module. - - - - A previous version of this module used concrete, unexported types as the - - skolems. This turned out to be unsound in the presence of type families. - - There were 3 somewhat distinct issues: - - - - 1. Using closed type families, it is possible to test whether two concrete - - types are equal, even if one of them is not directly importable. - - - - 2. Using just open type families, it is possible to test "at least 2 of - - these n+1 types are equal", thus using the pigeonhole principle to thwart - - any scheme based on having only a finite number of shared skolem types. - - - - 3. Using just pattern matching of types by unification, it is possible - - to extract the skolem types from the application the `Forall p` expands - - to. (Although type families are probably still needed to exploit this.) - - - - András Kovács and Ørjan Johansen independently realized that skolems - - themselves made as type family applications can be used to solve the first - - two problems (and discovered the third problem in the process). As a bonus, - - the resulting code is easy to make polykinded. - - - - Problem 1 is solved by making the type family have no instances, forcing - - GHC to make no assumption about what type a skolem is. - - - - Problem 2 is solved by parametrizing the skolem on the predicate tested - - for. (This is a known trick in predicate logic.) - - - - Problem 3 is solved by making the `Forall p` application expand to a type - - class, and have the *actual* test constraint be a superclass constraint on - - that type class, thus preventing the user directly accessing it. - - - - An unfortunate side effect of the new method is that it tends to trigger - - spurious errors from GHC test for cycles in superclass constraints. András - - Kovács discovered that these can be silenced by yet another use of a type - - family. - - - - David Feuer points out a remaining doubt about the soundness of this scheme: - - GHC *does* know that the skolems created from a single predicate `p` are - - equal. This could in theory apply even if the skolems come from two - - *distinct* invocations of `Forall p`. - - - - However, we don't know any way of bringing two such skolems in contact with - - each other to create an actual exploit. It would seem to require `p` to - - already contain its own skolem, despite there being (hopefully) no way to - - extract it from `Forall p` in order to tie the knot. - -} - --- The `Skolem` type family represents skolem variables; do not export! --- If GHC supports it, these might be made closed with no instances. +class (forall a. p a) => Forall (p :: k -> Constraint) +instance (forall a. p a) => Forall (p :: k -> Constraint) -type family Skolem (p :: k -> Constraint) :: k +-- | Instantiate a quantified @'Forall' p@ constraint at type @a@. +inst :: forall p a. Forall p :- p a +inst = Sub Dict --- The outer `Forall` type family prevents GHC from giving a spurious --- superclass cycle error. --- The inner `Forall_` class prevents the skolem from leaking to the user, --- which would be disastrous. +data Dict1 p where + Dict1 :: (forall a. p a) => Dict1 p --- | A representation of the quantified constraint @forall a. p a@. -type family Forall (p :: k -> Constraint) :: Constraint -type instance Forall p = Forall_ p -class p (Skolem p) => Forall_ (p :: k -> Constraint) -instance p (Skolem p) => Forall_ (p :: k -> Constraint) +forallish :: forall p. Dict1 p -> Dict (Forall p) +forallish Dict1 = Dict --- | Instantiate a quantified @'Forall' p@ constraint at type @a@. -inst :: forall p a. Forall p :- p a -inst = unsafeCoerce (Sub Dict :: Forall p :- p (Skolem p)) +forall_ :: forall p. (forall a. Dict (p a)) -> Dict (Forall p) +forall_ d = forallish (unsafeCoerce d) -- | Composition for constraints. class p (f a) => ComposeC (p :: k2 -> Constraint) (f :: k1 -> k2) (a :: k1) @@ -149,7 +79,7 @@ instance Forall (Q p t) => ForallT p t -- | Instantiate a quantified @'ForallT' p t@ constraint at types @f@ and @a@. -instT :: forall KVS(k1 k2 k3 k4) (p :: k4 -> Constraint) (t :: (k1 -> k2) -> k3 -> k4) (f :: k1 -> k2) (a :: k3). ForallT p t :- p (t f a) +instT :: forall k1 k2 k3 k4 (p :: k4 -> Constraint) (t :: (k1 -> k2) -> k3 -> k4) (f :: k1 -> k2) (a :: k3). ForallT p t :- p (t f a) instT = Sub $ case inst :: Forall (Q p t) :- Q p t f of { Sub Dict -> case inst :: Forall (R p t f) :- R p t f a of @@ -173,25 +103,23 @@ -- | Instantiate a quantified @'ForallV' p@ constraint as @c@, where -- @c ~ p a1 a2 ... an@. class InstV (p :: k) c | k c -> p where - type ForallV' (p :: k) :: Constraint - instV :: ForallV p :- c + type ForallV' (p :: k) :: Constraint + instV :: ForallV p :- c instance p ~ c => InstV (p :: Constraint) c where - type ForallV' (p :: Constraint) = p - instV = Sub Dict + type ForallV' (p :: Constraint) = p + instV = Sub Dict -- Treating 1 argument specially rather than recursing as a bit of (premature?) -- optimization instance p a ~ c => InstV (p :: k -> Constraint) c where - type ForallV' (p :: k -> Constraint) = Forall p - instV = Sub $ case inst :: Forall p :- c of - Sub Dict -> Dict + type ForallV' (p :: k -> Constraint) = Forall p + instV = Sub $ case inst :: Forall p :- c of + Sub Dict -> Dict instance InstV (p a) c => InstV (p :: k1 -> k2 -> k3) c where - type ForallV' (p :: k1 -> k2 -> k3) = ForallF ForallV p - instV = Sub $ case instF :: ForallF ForallV p :- ForallV (p a) of - Sub Dict -> case instV :: ForallV (p a) :- c of - Sub Dict -> Dict + type ForallV' (p :: k1 -> k2 -> k3) = ForallF ForallV p + instV = Sub $ case instF :: ForallF ForallV p :- ForallV (p a) of + Sub Dict -> case instV :: ForallV (p a) :- c of + Sub Dict -> Dict -forall :: forall p. (forall a. Dict (p a)) -> Dict (Forall p) -forall d = case d :: Dict (p (Skolem p)) of Dict -> Dict diff --git a/src/Data/Constraint/Lifting.hs b/src/Data/Constraint/Lifting.hs --- a/src/Data/Constraint/Lifting.hs +++ b/src/Data/Constraint/Lifting.hs @@ -3,12 +3,11 @@ {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE ConstraintKinds #-} -{-# LANGUAGE DefaultSignatures #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} -{-# OPTIONS_GHC -fno-warn-deprecations #-} + module Data.Constraint.Lifting ( Lifting(..) , Lifting2(..) @@ -25,10 +24,8 @@ import Control.Monad.IO.Class import Control.Monad.RWS.Class import Control.Monad.Trans.Cont -import Control.Monad.Trans.Error import Control.Monad.Trans.Except import Control.Monad.Trans.Identity -import Control.Monad.Trans.List import Control.Monad.Trans.Maybe import Control.Monad.Trans.Reader import Control.Monad.Trans.RWS.Lazy as Lazy @@ -40,9 +37,6 @@ import Data.Binary import Data.Complex import Data.Constraint -#if __GLASGOW_HASKELL__ < 710 -import Data.Foldable -#endif import Data.Functor.Classes import Data.Functor.Compose as Functor import Data.Functor.Identity @@ -50,16 +44,7 @@ import Data.Functor.Reverse as Functor import Data.Functor.Sum as Functor import Data.Hashable -#if __GLASGOW_HASKELL__ < 710 -import Data.Monoid -#endif import Data.Ratio -#if !(MIN_VERSION_base(4,11,0)) -import Data.Semigroup -#endif -#if __GLASGOW_HASKELL__ < 710 -import Data.Traversable -#endif import GHC.Arr class Lifting p f where @@ -118,7 +103,6 @@ instance Applicative f => Lifting Applicative (Compose f) where lifting = Sub Dict instance Alternative f => Lifting Alternative (Compose f) where lifting = Sub Dict -- overconstrained -#if MIN_VERSION_transformers(0,5,0) instance Show1 f => Lifting Show1 (Compose f) where lifting = Sub Dict instance Eq1 f => Lifting Eq1 (Compose f) where lifting = Sub Dict instance Ord1 f => Lifting Ord1 (Compose f) where lifting = Sub Dict @@ -127,16 +111,6 @@ instance (Ord1 f, Ord1 g) => Lifting Ord (Compose f g) where lifting = Sub Dict instance (Read1 f, Read1 g) => Lifting Read (Compose f g) where lifting = Sub Dict instance (Show1 f, Show1 g) => Lifting Show (Compose f g) where lifting = Sub Dict -#else -instance (Functor f, Show1 f) => Lifting Show1 (Compose f) where lifting = Sub Dict -instance (Functor f, Eq1 f) => Lifting Eq1 (Compose f) where lifting = Sub Dict -instance (Functor f, Ord1 f) => Lifting Ord1 (Compose f) where lifting = Sub Dict -instance (Functor f, Read1 f) => Lifting Read1 (Compose f) where lifting = Sub Dict -instance (Functor f, Eq1 f, Eq1 g) => Lifting Eq (Compose f g) where lifting = Sub Dict -instance (Functor f, Ord1 f, Ord1 g) => Lifting Ord (Compose f g) where lifting = Sub Dict -instance (Functor f, Read1 f, Read1 g) => Lifting Read (Compose f g) where lifting = Sub Dict -instance (Functor f, Show1 f, Show1 g) => Lifting Show (Compose f g) where lifting = Sub Dict -#endif instance Functor f => Lifting Functor (Functor.Product f) where lifting = Sub Dict instance Foldable f => Lifting Foldable (Functor.Product f) where lifting = Sub Dict @@ -199,22 +173,6 @@ instance Lifting MonadFix (ReaderT e) where lifting = Sub Dict instance Lifting MonadIO (ReaderT e) where lifting = Sub Dict -instance Lifting Functor (ErrorT e) where lifting = Sub Dict -instance Lifting Foldable (ErrorT e) where lifting = Sub Dict -instance Lifting Traversable (ErrorT e) where lifting = Sub Dict -instance Error e => Lifting Monad (ErrorT e) where lifting = Sub Dict -instance Error e => Lifting MonadFix (ErrorT e) where lifting = Sub Dict -instance Error e => Lifting MonadPlus (ErrorT e) where lifting = Sub Dict -- overconstrained! -instance Error e => Lifting MonadIO (ErrorT e) where lifting = Sub Dict -instance Show e => Lifting Show1 (ErrorT e) where lifting = Sub Dict -instance Eq e => Lifting Eq1 (ErrorT e) where lifting = Sub Dict -instance Ord e => Lifting Ord1 (ErrorT e) where lifting = Sub Dict -instance Read e => Lifting Read1 (ErrorT e) where lifting = Sub Dict -instance (Show e, Show1 m) => Lifting Show (ErrorT e m) where lifting = Sub Dict -instance (Eq e, Eq1 m) => Lifting Eq (ErrorT e m) where lifting = Sub Dict -instance (Ord e, Ord1 m) => Lifting Ord (ErrorT e m) where lifting = Sub Dict -instance (Read e, Read1 m) => Lifting Read (ErrorT e m) where lifting = Sub Dict - instance Lifting Functor (ExceptT e) where lifting = Sub Dict instance Lifting Foldable (ExceptT e) where lifting = Sub Dict instance Lifting Traversable (ExceptT e) where lifting = Sub Dict @@ -290,24 +248,6 @@ instance Ord1 m => Lifting Ord (IdentityT m) where lifting = Sub Dict instance Eq1 m => Lifting Eq (IdentityT m) where lifting = Sub Dict -instance Lifting Functor ListT where lifting = Sub Dict -instance Lifting Applicative ListT where lifting = Sub Dict -instance Lifting Alternative ListT where lifting = Sub Dict -- overconstrained -instance Lifting Monad ListT where lifting = Sub Dict --- instance Lifting MonadFix ListT where lifting = Sub Dict -instance Lifting MonadPlus ListT where lifting = Sub Dict -- overconstrained -instance Lifting Foldable ListT where lifting = Sub Dict -instance Lifting Traversable ListT where lifting = Sub Dict -instance Lifting MonadIO ListT where lifting = Sub Dict -instance Lifting Show1 ListT where lifting = Sub Dict -instance Lifting Read1 ListT where lifting = Sub Dict -instance Lifting Ord1 ListT where lifting = Sub Dict -instance Lifting Eq1 ListT where lifting = Sub Dict -instance Show1 m => Lifting Show (ListT m) where lifting = Sub Dict -instance Read1 m => Lifting Read (ListT m) where lifting = Sub Dict -instance Ord1 m => Lifting Ord (ListT m) where lifting = Sub Dict -instance Eq1 m => Lifting Eq (ListT m) where lifting = Sub Dict - instance Lifting Functor MaybeT where lifting = Sub Dict instance Lifting Monad MaybeT where lifting = Sub Dict -- instance Lifting MonadFix MaybeT where lifting = Sub Dict @@ -372,11 +312,9 @@ instance Lifting Read Identity where lifting = Sub Dict instance Lifting MonadCont MaybeT where lifting = Sub Dict -instance Lifting MonadCont ListT where lifting = Sub Dict instance Lifting MonadCont IdentityT where lifting = Sub Dict instance Monoid w => Lifting MonadCont (Strict.WriterT w) where lifting = Sub Dict instance Monoid w => Lifting MonadCont (Lazy.WriterT w) where lifting = Sub Dict -instance Error e => Lifting MonadCont (ErrorT e) where lifting = Sub Dict instance Lifting MonadCont (ExceptT w) where lifting = Sub Dict instance Lifting MonadCont (Strict.StateT s) where lifting = Sub Dict instance Lifting MonadCont (Lazy.StateT s) where lifting = Sub Dict @@ -385,7 +323,6 @@ instance Monoid w => Lifting MonadCont (Lazy.RWST r w s) where lifting = Sub Dict instance Lifting (MonadError e) MaybeT where lifting = Sub Dict -instance Lifting (MonadError e) ListT where lifting = Sub Dict instance Lifting (MonadError e) IdentityT where lifting = Sub Dict instance Monoid w => Lifting (MonadError e) (Strict.WriterT w) where lifting = Sub Dict instance Monoid w => Lifting (MonadError e) (Lazy.WriterT w) where lifting = Sub Dict @@ -397,28 +334,23 @@ instance Lifting (MonadRWS r w s) MaybeT where lifting = Sub Dict instance Lifting (MonadRWS r w s) IdentityT where lifting = Sub Dict -instance Error e => Lifting (MonadRWS r w s) (ErrorT e) where lifting = Sub Dict instance Lifting (MonadRWS r w s) (ExceptT e) where lifting = Sub Dict instance Lifting (MonadReader r) MaybeT where lifting = Sub Dict -instance Lifting (MonadReader r) ListT where lifting = Sub Dict instance Lifting (MonadReader r) IdentityT where lifting = Sub Dict instance Monoid w => Lifting (MonadReader r) (Strict.WriterT w) where lifting = Sub Dict instance Monoid w => Lifting (MonadReader r) (Lazy.WriterT w) where lifting = Sub Dict instance Lifting (MonadReader r) (Strict.StateT s) where lifting = Sub Dict instance Lifting (MonadReader r) (Lazy.StateT s) where lifting = Sub Dict instance Lifting (MonadReader r) (ExceptT e) where lifting = Sub Dict -instance Error e => Lifting (MonadReader r) (ErrorT e) where lifting = Sub Dict instance Lifting (MonadReader r) (ContT r') where lifting = Sub Dict instance Lifting (MonadState s) MaybeT where lifting = Sub Dict -instance Lifting (MonadState s) ListT where lifting = Sub Dict instance Lifting (MonadState s) IdentityT where lifting = Sub Dict instance Monoid w => Lifting (MonadState s) (Strict.WriterT w) where lifting = Sub Dict instance Monoid w => Lifting (MonadState s) (Lazy.WriterT w) where lifting = Sub Dict instance Lifting (MonadState s) (ReaderT r) where lifting = Sub Dict instance Lifting (MonadState s) (ExceptT e) where lifting = Sub Dict -instance Error e => Lifting (MonadState s) (ErrorT e) where lifting = Sub Dict instance Lifting (MonadState s) (ContT r') where lifting = Sub Dict class Lifting2 p f where diff --git a/src/Data/Constraint/Nat.hs b/src/Data/Constraint/Nat.hs --- a/src/Data/Constraint/Nat.hs +++ b/src/Data/Constraint/Nat.hs @@ -1,25 +1,23 @@ {-# LANGUAGE CPP #-} {-# LANGUAGE DataKinds #-} +{-# LANGUAGE MagicHash #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} -{-# LANGUAGE KindSignatures #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE Trustworthy #-} {-# LANGUAGE UndecidableInstances #-} -#if __GLASGOW_HASKELL__ >= 805 {-# LANGUAGE NoStarIsType #-} -#endif -- | Utilities for working with 'KnownNat' constraints. -- -- This module is only available on GHC 8.0 or later. module Data.Constraint.Nat - ( Min, Max, Lcm, Gcd, Divides, Div, Mod - , plusNat, minusNat, timesNat, powNat, minNat, maxNat, gcdNat, lcmNat, divNat, modNat + ( Min, Max, Lcm, Gcd, Divides, Div, Mod, Log2 + , plusNat, minusNat, timesNat, powNat, minNat, maxNat, gcdNat, lcmNat, divNat, modNat, log2Nat , plusZero, minusZero, timesZero, timesOne, powZero, powOne, maxZero, minZero, gcdZero, gcdOne, lcmZero, lcmOne , plusAssociates, timesAssociates, minAssociates, maxAssociates, gcdAssociates, lcmAssociates , plusCommutes, timesCommutes, minCommutes, maxCommutes, gcdCommutes, lcmCommutes @@ -39,6 +37,7 @@ , euclideanNat , plusMod, timesMod , modBound + , log2Pow , dividesDef , timesDiv , eqLe, leEq, leId, leTrans @@ -47,21 +46,27 @@ ) where import Data.Constraint +import Data.Constraint.Unsafe import Data.Proxy import Data.Type.Bool -import GHC.TypeLits +import GHC.TypeNats +import qualified Numeric.Natural as Nat + +#if MIN_VERSION_base(4,15,0) +import GHC.Num.Natural (naturalLog2) +#else +import GHC.Exts (Int(..)) +import GHC.Integer.Logarithms (integerLog2#) +#endif + +#if !MIN_VERSION_base(4,18,0) import Unsafe.Coerce +#endif type family Min (m::Nat) (n::Nat) :: Nat where Min m n = If (n <=? m) n m type family Max (m::Nat) (n::Nat) :: Nat where Max m n = If (n <=? m) m n -#if !(MIN_VERSION_base(4,11,0)) -type family Div (m::Nat) (n::Nat) :: Nat where - Div m 1 = m -type family Mod (m::Nat) (n::Nat) :: Nat where - Mod 0 m = 0 -#endif type family Gcd (m::Nat) (n::Nat) :: Nat where Gcd m m = m type family Lcm (m::Nat) (n::Nat) :: Nat where @@ -69,74 +74,94 @@ type Divides n m = n ~ Gcd n m +#if !MIN_VERSION_base(4,18,0) newtype Magic n = Magic (KnownNat n => Dict (KnownNat n)) +#endif -magic :: forall n m o. (Integer -> Integer -> Integer) -> (KnownNat n, KnownNat m) :- KnownNat o -magic f = Sub $ unsafeCoerce (Magic Dict) (natVal (Proxy :: Proxy n) `f` natVal (Proxy :: Proxy m)) +magicNNN :: forall n m o. (Nat.Natural -> Nat.Natural -> Nat.Natural) -> (KnownNat n, KnownNat m) :- KnownNat o +#if MIN_VERSION_base(4,18,0) +magicNNN f = Sub $ withKnownNat @o (unsafeSNat (natVal (Proxy @n) `f` natVal (Proxy @m))) Dict +#else +magicNNN f = Sub $ unsafeCoerce (Magic Dict) (natVal (Proxy @n) `f` natVal (Proxy @m)) +#endif -axiom :: forall a b. Dict (a ~ b) -axiom = unsafeCoerce (Dict :: Dict (a ~ a)) +magicNN :: forall n m. (Nat.Natural -> Nat.Natural) -> KnownNat n :- KnownNat m +#if MIN_VERSION_base(4,18,0) +magicNN f = Sub $ withKnownNat @m (unsafeSNat (f (natVal (Proxy @n)))) Dict +#else +magicNN f = Sub $ unsafeCoerce (Magic Dict) (f (natVal (Proxy :: Proxy n))) +#endif -axiomLe :: forall a b. Dict (a <= b) -axiomLe = axiom +axiomLe :: forall (a :: Nat) (b :: Nat). Dict (a <= b) +axiomLe = unsafeAxiom -eqLe :: (a ~ b) :- (a <= b) +eqLe :: forall (a :: Nat) (b :: Nat). (a ~ b) :- (a <= b) eqLe = Sub Dict dividesGcd :: forall a b c. (Divides a b, Divides a c) :- Divides a (Gcd b c) -dividesGcd = Sub axiom +dividesGcd = Sub unsafeAxiom dividesLcm :: forall a b c. (Divides a c, Divides b c) :- Divides (Lcm a b) c -dividesLcm = Sub axiom +dividesLcm = Sub unsafeAxiom gcdCommutes :: forall a b. Dict (Gcd a b ~ Gcd b a) -gcdCommutes = axiom +gcdCommutes = unsafeAxiom lcmCommutes :: forall a b. Dict (Lcm a b ~ Lcm b a) -lcmCommutes = axiom +lcmCommutes = unsafeAxiom gcdZero :: forall a. Dict (Gcd 0 a ~ a) -gcdZero = axiom +gcdZero = unsafeAxiom gcdOne :: forall a. Dict (Gcd 1 a ~ 1) -gcdOne = axiom +gcdOne = unsafeAxiom lcmZero :: forall a. Dict (Lcm 0 a ~ 0) -lcmZero = axiom +lcmZero = unsafeAxiom lcmOne :: forall a. Dict (Lcm 1 a ~ a) -lcmOne = axiom +lcmOne = unsafeAxiom gcdNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (Gcd n m) -gcdNat = magic gcd +gcdNat = magicNNN gcd lcmNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (Lcm n m) -lcmNat = magic lcm +lcmNat = magicNNN lcm plusNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (n + m) -plusNat = magic (+) +plusNat = magicNNN (+) minusNat :: forall n m. (KnownNat n, KnownNat m, m <= n) :- KnownNat (n - m) -minusNat = Sub $ case magic @n @m (-) of Sub r -> r +minusNat = Sub $ case magicNNN @n @m (-) of Sub r -> r minNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (Min n m) -minNat = magic min +minNat = magicNNN min maxNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (Max n m) -maxNat = magic max +maxNat = magicNNN max timesNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (n * m) -timesNat = magic (*) +timesNat = magicNNN (*) powNat :: forall n m. (KnownNat n, KnownNat m) :- KnownNat (n ^ m) -powNat = magic (^) +powNat = magicNNN (^) divNat :: forall n m. (KnownNat n, KnownNat m, 1 <= m) :- KnownNat (Div n m) -divNat = Sub $ case magic @n @m div of Sub r -> r +divNat = Sub $ case magicNNN @n @m div of Sub r -> r modNat :: forall n m. (KnownNat n, KnownNat m, 1 <= m) :- KnownNat (Mod n m) -modNat = Sub $ case magic @n @m mod of Sub r -> r +modNat = Sub $ case magicNNN @n @m mod of Sub r -> r +log2Nat :: forall n. (KnownNat n, 1 <= n) :- KnownNat (Log2 n) +log2Nat = Sub $ case magicNN @n log2 of Sub r -> r + where + log2 :: Nat.Natural -> Nat.Natural +#if MIN_VERSION_base(4,15,0) + log2 n = fromIntegral (naturalLog2 n) +#else + log2 n = fromIntegral (I# (integerLog2# (toInteger n))) +#endif + plusZero :: forall n. Dict ((n + 0) ~ n) plusZero = Dict @@ -150,109 +175,124 @@ timesOne = Dict minZero :: forall n. Dict (Min n 0 ~ 0) +#if MIN_VERSION_base(4,16,0) +minZero = unsafeAxiom +#else minZero = Dict +#endif maxZero :: forall n. Dict (Max n 0 ~ n) +#if MIN_VERSION_base(4,16,0) +maxZero = unsafeAxiom +#else maxZero = Dict +#endif powZero :: forall n. Dict ((n ^ 0) ~ 1) powZero = Dict leZero :: forall a. (a <= 0) :- (a ~ 0) -leZero = Sub axiom +leZero = Sub unsafeAxiom -zeroLe :: forall a. Dict (0 <= a) +zeroLe :: forall (a :: Nat). Dict (0 <= a) +#if MIN_VERSION_base(4,16,0) +zeroLe = unsafeAxiom +#else zeroLe = Dict +#endif plusMinusInverse1 :: forall n m. Dict (((m + n) - n) ~ m) -plusMinusInverse1 = axiom +plusMinusInverse1 = unsafeAxiom plusMinusInverse2 :: forall n m. (m <= n) :- (((m + n) - m) ~ n) -plusMinusInverse2 = Sub axiom +plusMinusInverse2 = Sub unsafeAxiom plusMinusInverse3 :: forall n m. (n <= m) :- (((m - n) + n) ~ m) -plusMinusInverse3 = Sub axiom +plusMinusInverse3 = Sub unsafeAxiom plusMonotone1 :: forall a b c. (a <= b) :- (a + c <= b + c) -plusMonotone1 = Sub axiom +plusMonotone1 = Sub unsafeAxiom plusMonotone2 :: forall a b c. (b <= c) :- (a + b <= a + c) -plusMonotone2 = Sub axiom +plusMonotone2 = Sub unsafeAxiom powMonotone1 :: forall a b c. (a <= b) :- ((a^c) <= (b^c)) -powMonotone1 = Sub axiom +powMonotone1 = Sub unsafeAxiom powMonotone2 :: forall a b c. (b <= c) :- ((a^b) <= (a^c)) -powMonotone2 = Sub axiom +powMonotone2 = Sub unsafeAxiom divMonotone1 :: forall a b c. (a <= b) :- (Div a c <= Div b c) -divMonotone1 = Sub axiom +divMonotone1 = Sub unsafeAxiom divMonotone2 :: forall a b c. (b <= c) :- (Div a c <= Div a b) -divMonotone2 = Sub axiom +divMonotone2 = Sub unsafeAxiom timesMonotone1 :: forall a b c. (a <= b) :- (a * c <= b * c) -timesMonotone1 = Sub axiom +timesMonotone1 = Sub unsafeAxiom timesMonotone2 :: forall a b c. (b <= c) :- (a * b <= a * c) -timesMonotone2 = Sub axiom +timesMonotone2 = Sub unsafeAxiom minMonotone1 :: forall a b c. (a <= b) :- (Min a c <= Min b c) -minMonotone1 = Sub axiom +minMonotone1 = Sub unsafeAxiom minMonotone2 :: forall a b c. (b <= c) :- (Min a b <= Min a c) -minMonotone2 = Sub axiom +minMonotone2 = Sub unsafeAxiom maxMonotone1 :: forall a b c. (a <= b) :- (Max a c <= Max b c) -maxMonotone1 = Sub axiom +maxMonotone1 = Sub unsafeAxiom maxMonotone2 :: forall a b c. (b <= c) :- (Max a b <= Max a c) -maxMonotone2 = Sub axiom +maxMonotone2 = Sub unsafeAxiom powOne :: forall n. Dict ((n ^ 1) ~ n) -powOne = axiom +powOne = unsafeAxiom plusMod :: forall a b c. (1 <= c) :- (Mod (a + b) c ~ Mod (Mod a c + Mod b c) c) -plusMod = Sub axiom +plusMod = Sub unsafeAxiom timesMod :: forall a b c. (1 <= c) :- (Mod (a * b) c ~ Mod (Mod a c * Mod b c) c) -timesMod = Sub axiom +timesMod = Sub unsafeAxiom modBound :: forall m n. (1 <= n) :- (Mod m n <= n) -modBound = Sub axiom +modBound = Sub unsafeAxiom +log2Pow :: forall n. Dict (Log2 (2 ^ n) ~ n) +log2Pow = unsafeAxiom + euclideanNat :: (1 <= c) :- (a ~ (c * Div a c + Mod a c)) -euclideanNat = Sub axiom +euclideanNat = Sub unsafeAxiom plusCommutes :: forall n m. Dict ((m + n) ~ (n + m)) -plusCommutes = axiom +plusCommutes = unsafeAxiom timesCommutes :: forall n m. Dict ((m * n) ~ (n * m)) -timesCommutes = axiom +timesCommutes = unsafeAxiom minCommutes :: forall n m. Dict (Min m n ~ Min n m) -minCommutes = axiom +minCommutes = unsafeAxiom maxCommutes :: forall n m. Dict (Max m n ~ Max n m) -maxCommutes = axiom +maxCommutes = unsafeAxiom plusAssociates :: forall m n o. Dict (((m + n) + o) ~ (m + (n + o))) -plusAssociates = axiom +plusAssociates = unsafeAxiom timesAssociates :: forall m n o. Dict (((m * n) * o) ~ (m * (n * o))) -timesAssociates = axiom +timesAssociates = unsafeAxiom minAssociates :: forall m n o. Dict (Min (Min m n) o ~ Min m (Min n o)) -minAssociates = axiom +minAssociates = unsafeAxiom maxAssociates :: forall m n o. Dict (Max (Max m n) o ~ Max m (Max n o)) -maxAssociates = axiom +maxAssociates = unsafeAxiom gcdAssociates :: forall a b c. Dict (Gcd (Gcd a b) c ~ Gcd a (Gcd b c)) -gcdAssociates = axiom +gcdAssociates = unsafeAxiom lcmAssociates :: forall a b c. Dict (Lcm (Lcm a b) c ~ Lcm a (Lcm b c)) -lcmAssociates = axiom +lcmAssociates = unsafeAxiom minIsIdempotent :: forall n. Dict (Min n n ~ n) minIsIdempotent = Dict @@ -267,87 +307,90 @@ lcmIsIdempotent = Dict minDistributesOverPlus :: forall n m o. Dict ((n + Min m o) ~ Min (n + m) (n + o)) -minDistributesOverPlus = axiom +minDistributesOverPlus = unsafeAxiom minDistributesOverTimes :: forall n m o. Dict ((n * Min m o) ~ Min (n * m) (n * o)) -minDistributesOverTimes = axiom +minDistributesOverTimes = unsafeAxiom minDistributesOverPow1 :: forall n m o. Dict ((Min n m ^ o) ~ Min (n ^ o) (m ^ o)) -minDistributesOverPow1 = axiom +minDistributesOverPow1 = unsafeAxiom minDistributesOverPow2 :: forall n m o. Dict ((n ^ Min m o) ~ Min (n ^ m) (n ^ o)) -minDistributesOverPow2 = axiom +minDistributesOverPow2 = unsafeAxiom minDistributesOverMax :: forall n m o. Dict (Max n (Min m o) ~ Min (Max n m) (Max n o)) -minDistributesOverMax = axiom +minDistributesOverMax = unsafeAxiom maxDistributesOverPlus :: forall n m o. Dict ((n + Max m o) ~ Max (n + m) (n + o)) -maxDistributesOverPlus = axiom +maxDistributesOverPlus = unsafeAxiom maxDistributesOverTimes :: forall n m o. Dict ((n * Max m o) ~ Max (n * m) (n * o)) -maxDistributesOverTimes = axiom +maxDistributesOverTimes = unsafeAxiom maxDistributesOverPow1 :: forall n m o. Dict ((Max n m ^ o) ~ Max (n ^ o) (m ^ o)) -maxDistributesOverPow1 = axiom +maxDistributesOverPow1 = unsafeAxiom maxDistributesOverPow2 :: forall n m o. Dict ((n ^ Max m o) ~ Max (n ^ m) (n ^ o)) -maxDistributesOverPow2 = axiom +maxDistributesOverPow2 = unsafeAxiom maxDistributesOverMin :: forall n m o. Dict (Min n (Max m o) ~ Max (Min n m) (Min n o)) -maxDistributesOverMin = axiom +maxDistributesOverMin = unsafeAxiom plusDistributesOverTimes :: forall n m o. Dict ((n * (m + o)) ~ (n * m + n * o)) -plusDistributesOverTimes = axiom +plusDistributesOverTimes = unsafeAxiom timesDistributesOverPow :: forall n m o. Dict ((n ^ (m + o)) ~ (n ^ m * n ^ o)) -timesDistributesOverPow = axiom +timesDistributesOverPow = unsafeAxiom timesDistributesOverGcd :: forall n m o. Dict ((n * Gcd m o) ~ Gcd (n * m) (n * o)) -timesDistributesOverGcd = axiom +timesDistributesOverGcd = unsafeAxiom timesDistributesOverLcm :: forall n m o. Dict ((n * Lcm m o) ~ Lcm (n * m) (n * o)) -timesDistributesOverLcm = axiom +timesDistributesOverLcm = unsafeAxiom plusIsCancellative :: forall n m o. ((n + m) ~ (n + o)) :- (m ~ o) -plusIsCancellative = Sub axiom +plusIsCancellative = Sub unsafeAxiom timesIsCancellative :: forall n m o. (1 <= n, (n * m) ~ (n * o)) :- (m ~ o) -timesIsCancellative = Sub axiom +timesIsCancellative = Sub unsafeAxiom gcdDistributesOverLcm :: forall a b c. Dict (Gcd (Lcm a b) c ~ Lcm (Gcd a c) (Gcd b c)) -gcdDistributesOverLcm = axiom +gcdDistributesOverLcm = unsafeAxiom lcmDistributesOverGcd :: forall a b c. Dict (Lcm (Gcd a b) c ~ Gcd (Lcm a c) (Lcm b c)) -lcmDistributesOverGcd = axiom +lcmDistributesOverGcd = unsafeAxiom dividesPlus :: (Divides a b, Divides a c) :- Divides a (b + c) -dividesPlus = Sub axiom +dividesPlus = Sub unsafeAxiom -dividesTimes :: (Divides a b, Divides a c) :- Divides a (b * c) -dividesTimes = Sub axiom +dividesTimes :: Divides a b :- Divides a (b * c) +dividesTimes = Sub unsafeAxiom dividesMin :: (Divides a b, Divides a c) :- Divides a (Min b c) -dividesMin = Sub axiom +dividesMin = Sub unsafeAxiom dividesMax :: (Divides a b, Divides a c) :- Divides a (Max b c) -dividesMax = Sub axiom +dividesMax = Sub unsafeAxiom -dividesDef :: forall a b. Divides a b :- ((a * Div b a) ~ b) -dividesDef = Sub axiom +-- This `dividesDef` is simpler and more convenient than Divides a b :- ((a * Div b a) ~ b) +-- because the latter can be easily derived via 'euclideanNat', but not vice versa. +dividesDef :: forall a b. Divides a b :- (Mod b a ~ 0) +dividesDef = Sub unsafeAxiom + dividesPow :: (1 <= n, Divides a b) :- Divides a (b^n) -dividesPow = Sub axiom +dividesPow = Sub unsafeAxiom timesDiv :: forall a b. Dict ((a * Div b a) <= b) -timesDiv = axiom +timesDiv = unsafeAxiom -- (<=) is an internal category in the category of constraints. -leId :: forall a. Dict (a <= a) +leId :: forall (a :: Nat). Dict (a <= a) leId = Dict -leEq :: forall a b. (a <= b, b <= a) :- (a ~ b) -leEq = Sub axiom +leEq :: forall (a :: Nat) (b :: Nat). (a <= b, b <= a) :- (a ~ b) +leEq = Sub unsafeAxiom -leTrans :: forall a b c. (b <= c, a <= b) :- (a <= c) +leTrans :: forall (a :: Nat) (b :: Nat) (c :: Nat). (b <= c, a <= b) :- (a <= c) leTrans = Sub (axiomLe @a @c) diff --git a/src/Data/Constraint/Symbol.hs b/src/Data/Constraint/Symbol.hs --- a/src/Data/Constraint/Symbol.hs +++ b/src/Data/Constraint/Symbol.hs @@ -7,11 +7,11 @@ {-# LANGUAGE RankNTypes #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} +{-# LANGUAGE CPP #-} -- | Utilities for working with 'KnownSymbol' constraints. --- --- This module is only available on GHC 8.0 or later. module Data.Constraint.Symbol - ( type (++) + ( type AppendSymbol + , type (++) , type Take , type Drop , type Length @@ -37,44 +37,63 @@ import Data.Constraint import Data.Constraint.Nat +import Data.Constraint.Unsafe import Data.Proxy import GHC.TypeLits +#if MIN_VERSION_base(4,18,0) +import qualified GHC.TypeNats as TN +#else import Unsafe.Coerce +#endif -type family (++) :: Symbol -> Symbol -> Symbol where +-- | An infix synonym for 'AppendSymbol'. +type (m :: Symbol) ++ (n :: Symbol) = AppendSymbol m n +infixr 5 ++ + type family Take :: Nat -> Symbol -> Symbol where type family Drop :: Nat -> Symbol -> Symbol where type family Length :: Symbol -> Nat where -- implementation details +#if !MIN_VERSION_base(4,18,0) newtype Magic n = Magic (KnownSymbol n => Dict (KnownSymbol n)) +#endif magicNSS :: forall n m o. (Int -> String -> String) -> (KnownNat n, KnownSymbol m) :- KnownSymbol o -magicNSS f = Sub $ unsafeCoerce (Magic Dict) (fromIntegral (natVal (Proxy :: Proxy n)) `f` symbolVal (Proxy :: Proxy m)) +#if MIN_VERSION_base(4,18,0) +magicNSS f = Sub $ withKnownSymbol (unsafeSSymbol @o (fromIntegral (natVal (Proxy @n)) `f` symbolVal (Proxy @m))) Dict +#else +magicNSS f = Sub $ unsafeCoerce (Magic Dict) (fromIntegral (natVal (Proxy @n)) `f` symbolVal (Proxy @m)) +#endif magicSSS :: forall n m o. (String -> String -> String) -> (KnownSymbol n, KnownSymbol m) :- KnownSymbol o -magicSSS f = Sub $ unsafeCoerce (Magic Dict) (symbolVal (Proxy :: Proxy n) `f` symbolVal (Proxy :: Proxy m)) +#if MIN_VERSION_base(4,18,0) +magicSSS f = Sub $ withKnownSymbol (unsafeSSymbol @o (symbolVal (Proxy @n) `f` symbolVal (Proxy @m))) Dict +#else +magicSSS f = Sub $ unsafeCoerce (Magic Dict) (symbolVal (Proxy @n) `f` symbolVal (Proxy @m)) +#endif magicSN :: forall a n. (String -> Int) -> KnownSymbol a :- KnownNat n -magicSN f = Sub $ unsafeCoerce (Magic Dict) (toInteger (f (symbolVal (Proxy :: Proxy a)))) - -axiom :: forall a b. Dict (a ~ b) -axiom = unsafeCoerce (Dict :: Dict (a ~ a)) +#if MIN_VERSION_base(4,18,0) +magicSN f = Sub $ TN.withKnownNat (unsafeSNat @n (fromIntegral (f (symbolVal (Proxy :: Proxy a))))) Dict +#else +magicSN f = Sub $ unsafeCoerce (Magic Dict) (toInteger (f (symbolVal (Proxy @a)))) +#endif --- axioms and operations +-- operations -appendSymbol :: (KnownSymbol a, KnownSymbol b) :- KnownSymbol (a ++ b) +appendSymbol :: (KnownSymbol a, KnownSymbol b) :- KnownSymbol (AppendSymbol a b) appendSymbol = magicSSS (++) -appendUnit1 :: forall a. Dict (("" ++ a) ~ a) -appendUnit1 = axiom +appendUnit1 :: forall a. Dict (AppendSymbol "" a ~ a) +appendUnit1 = Dict -appendUnit2 :: forall a. Dict ((a ++ "") ~ a) -appendUnit2 = axiom +appendUnit2 :: forall a. Dict (AppendSymbol a "" ~ a) +appendUnit2 = Dict -appendAssociates :: forall a b c. Dict (((a ++ b) ++ c) ~ (a ++ (b ++ c))) -appendAssociates = axiom +appendAssociates :: forall a b c. Dict (AppendSymbol (AppendSymbol a b) c ~ AppendSymbol a (AppendSymbol b c)) +appendAssociates = unsafeAxiom takeSymbol :: forall n a. (KnownNat n, KnownSymbol a) :- KnownSymbol (Take n a) takeSymbol = magicNSS take @@ -82,38 +101,38 @@ dropSymbol :: forall n a. (KnownNat n, KnownSymbol a) :- KnownSymbol (Drop n a) dropSymbol = magicNSS drop -takeAppendDrop :: forall n a. Dict (Take n a ++ Drop n a ~ a) -takeAppendDrop = axiom +takeAppendDrop :: forall n a. Dict (AppendSymbol (Take n a) (Drop n a) ~ a) +takeAppendDrop = unsafeAxiom lengthSymbol :: forall a. KnownSymbol a :- KnownNat (Length a) lengthSymbol = magicSN length takeLength :: forall n a. (Length a <= n) :- (Take n a ~ a) -takeLength = Sub axiom +takeLength = Sub unsafeAxiom take0 :: forall a. Dict (Take 0 a ~ "") -take0 = axiom +take0 = unsafeAxiom takeEmpty :: forall n. Dict (Take n "" ~ "") -takeEmpty = axiom +takeEmpty = unsafeAxiom dropLength :: forall n a. (Length a <= n) :- (Drop n a ~ "") -dropLength = Sub axiom +dropLength = Sub unsafeAxiom drop0 :: forall a. Dict (Drop 0 a ~ a) -drop0 = axiom +drop0 = unsafeAxiom dropEmpty :: forall n. Dict (Drop n "" ~ "") -dropEmpty = axiom +dropEmpty = unsafeAxiom lengthTake :: forall n a. Dict (Length (Take n a) <= n) -lengthTake = axiom +lengthTake = unsafeAxiom lengthDrop :: forall n a. Dict (Length a <= (Length (Drop n a) + n)) -lengthDrop = axiom +lengthDrop = unsafeAxiom dropDrop :: forall n m a. Dict (Drop n (Drop m a) ~ Drop (n + m) a) -dropDrop = axiom +dropDrop = unsafeAxiom takeTake :: forall n m a. Dict (Take n (Take m a) ~ Take (Min n m) a) -takeTake = axiom +takeTake = unsafeAxiom diff --git a/src/Data/Constraint/Unsafe.hs b/src/Data/Constraint/Unsafe.hs --- a/src/Data/Constraint/Unsafe.hs +++ b/src/Data/Constraint/Unsafe.hs @@ -1,4 +1,3 @@ -{-# LANGUAGE CPP #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ConstraintKinds #-} @@ -6,36 +5,48 @@ {-# LANGUAGE Rank2Types #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE Unsafe #-} -#if __GLASGOW_HASKELL__ >= 800 +{-# LANGUAGE CPP #-} {-# OPTIONS_GHC -fno-warn-redundant-constraints #-} -#endif ------------------------------------------------------------------------------ + -- | --- Module : Data.Constraint.Unsafe --- Copyright : (C) 2011-2015 Edward Kmett +-- Copyright : (C) 2011-2021 Edward Kmett -- License : BSD-style (see the file LICENSE) --- -- Maintainer : Edward Kmett -- Stability : experimental -- Portability : non-portable -- ----------------------------------------------------------------------------- +-- Unsafe utilities used throughout @constraints@. As the names suggest, these +-- functions are unsafe in general and can cause your program to segfault if +-- used improperly. Handle with care. + module Data.Constraint.Unsafe ( Coercible + , unsafeAxiom , unsafeCoerceConstraint , unsafeDerive , unsafeUnderive - -- * Sugar - , unsafeApplicative - , unsafeAlternative + +#if MIN_VERSION_base(4,18,0) + -- * Unsafely creating @GHC.TypeLits@ singleton values + , unsafeSChar + , unsafeSNat + , unsafeSSymbol +#endif ) where -import Control.Applicative -import Control.Monad import Data.Coerce import Data.Constraint import Unsafe.Coerce +#if MIN_VERSION_base(4,18,0) +import GHC.TypeLits (SChar, SNat, SSymbol) +import Numeric.Natural (Natural) +#endif + +-- | Unsafely create a dictionary for any constraint. +unsafeAxiom :: Dict c +unsafeAxiom = unsafeCoerce (Dict :: Dict ()) + -- | Coerce a dictionary unsafely from one type to another unsafeCoerceConstraint :: a :- b unsafeCoerceConstraint = unsafeCoerce refl @@ -48,19 +59,52 @@ unsafeUnderive :: Coercible n o => (o -> n) -> t n :- t o unsafeUnderive _ = unsafeCoerceConstraint +#if MIN_VERSION_base(4,18,0) +-- NB: if https://gitlab.haskell.org/ghc/ghc/-/issues/23478 were implemented, +-- then we could avoid using 'unsafeCoerce' in the definitions below. --- | Construct an Applicative instance from a Monad -unsafeApplicative :: forall m a. Monad m => (Applicative m => m a) -> m a -#if __GLASGOW_HASKELL__ < 710 -unsafeApplicative m = m \\ trans (unsafeCoerceConstraint :: Applicative (WrappedMonad m) :- Applicative m) ins -#else -unsafeApplicative m = m -#endif +-- | Unsafely create an 'SChar' value directly from a 'Char'. Use this function +-- with care: +-- +-- * The 'Char' value must match the 'Char' @c@ encoded in the return type +-- @'SChar' c@. +-- +-- * Be wary of using this function to create multiple values of type +-- @'SChar' T@, where @T@ is a type family that does not reduce (e.g., +-- @Any@ from "GHC.Exts"). If you do, GHC is liable to optimize away one of +-- the values and replace it with the other during a common subexpression +-- elimination pass. If the two values have different underlying 'Char' +-- values, this could be disastrous. +unsafeSChar :: Char -> SChar c +unsafeSChar = unsafeCoerce --- | Construct an Alternative instance from a MonadPlus -unsafeAlternative :: forall m a. MonadPlus m => (Alternative m => m a) -> m a -#if __GLASGOW_HASKELL__ < 710 -unsafeAlternative m = m \\ trans (unsafeCoerceConstraint :: Alternative (WrappedMonad m) :- Alternative m) ins -#else -unsafeAlternative m = m +-- | Unsafely create an 'SNat' value directly from a 'Natural'. Use this +-- function with care: +-- +-- * The 'Natural' value must match the 'Nat' @n@ encoded in the return type +-- @'SNat' n@. +-- +-- * Be wary of using this function to create multiple values of type +-- @'SNat' T@, where @T@ is a type family that does not reduce (e.g., +-- @Any@ from "GHC.Exts"). If you do, GHC is liable to optimize away one of +-- the values and replace it with the other during a common subexpression +-- elimination pass. If the two values have different underlying 'Natural' +-- values, this could be disastrous. +unsafeSNat :: Natural -> SNat n +unsafeSNat = unsafeCoerce + +-- | Unsafely create an 'SSymbol' value directly from a 'String'. Use this +-- function with care: +-- +-- * The 'String' value must match the 'Symbol' @s@ encoded in the return type +-- @'SSymbol' s@. +-- +-- * Be wary of using this function to create multiple values of type +-- @'SSymbol' T@, where @T@ is a type family that does not reduce (e.g., +-- @Any@ from "GHC.Exts"). If you do, GHC is liable to optimize away one of +-- the values and replace it with the other during a common subexpression +-- elimination pass. If the two values have different underlying 'String' +-- values, this could be disastrous. +unsafeSSymbol :: String -> SSymbol s +unsafeSSymbol = unsafeCoerce #endif diff --git a/tests/GH117Spec.hs b/tests/GH117Spec.hs new file mode 100644 --- /dev/null +++ b/tests/GH117Spec.hs @@ -0,0 +1,34 @@ +{-# LANGUAGE CPP #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE TypeApplications #-} + +module GH117Spec (main, spec) where + +import Test.Hspec + +#if __GLASGOW_HASKELL__ >= 902 +import Data.Constraint +import Data.Constraint.Char +import Data.Proxy +import GHC.TypeLits + +spec :: Spec +spec = + describe "GH #117" $ do + it "should evaluate `charToNat @'a'` to 97" $ + case charToNat @'a' of + Sub (Dict :: Dict (KnownNat n)) -> + natVal (Proxy @n) `shouldBe` 97 + it "should evaluate `natToChar @97` to 'a'" $ + case natToChar @97 of + Sub (Dict :: Dict (KnownChar c)) -> + charVal (Proxy @c) `shouldBe` 'a' +#else +spec :: Spec +spec = return () +#endif + +main :: IO () +main = hspec spec diff --git a/tests/GH55Spec.hs b/tests/GH55Spec.hs --- a/tests/GH55Spec.hs +++ b/tests/GH55Spec.hs @@ -1,22 +1,16 @@ -{-# LANGUAGE CPP #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ScopedTypeVariables #-} -{-# LANGUAGE TypeOperators #-} - -#if __GLASGOW_HASKELL__ >= 800 {-# LANGUAGE TypeApplications #-} -#endif +{-# LANGUAGE TypeOperators #-} module GH55Spec (main, spec) where -import Test.Hspec - -#if __GLASGOW_HASKELL__ >= 800 import Data.Constraint import Data.Constraint.Nat import GHC.TypeLits +import Test.Hspec newtype GF (n :: Nat) = GF Integer deriving (Eq, Show) @@ -48,10 +42,6 @@ spec = describe "GH #53" $ it "should normalize Lcm m m" $ z `shouldBe` (GF 0 :: GF (Lcm 5 5)) -#else -spec :: Spec -spec = return () -#endif main :: IO () main = hspec spec