constraints 0.4.1 → 0.4.1.1
raw patch · 3 files changed
+60/−19 lines, 3 filesPVP ok
version bump matches the API change (PVP)
API changes (from Hackage documentation)
Files
- Data/Constraint.hs +58/−18
- Data/Constraint/Forall.hs +1/−0
- constraints.cabal +1/−1
Data/Constraint.hs view
@@ -37,10 +37,12 @@ -- @ -- -- The need for this extension was first publicized in the paper+-- -- <http://research.microsoft.com/pubs/67439/gmap3.pdf Scrap your boilerplate with class: extensible generic functions>--- by Ralf Lämmel and Simon Peyton Jones in 2005, which shoehorned all the things they needed into a--- custom 'Sat' typeclass. --+-- by Ralf Lämmel and Simon Peyton Jones in 2005, which shoehorned all the+-- things they needed into a custom 'Sat' typeclass.+-- -- With @ConstraintKinds@ we can put into code a lot of tools for manipulating -- these new types without such awkward workarounds. ----------------------------------------------------------------------------@@ -77,12 +79,20 @@ #endif import GHC.Prim (Constraint) --- | Capture a dictionary for a given constraint+-- | Values of type @'Dict' p@ capture a dictionary for a constraint of type @p@. -- -- e.g. ----- @Dict :: Dict (Eq Int)@ captures a dictionary that proves we have 'instance Eq Int'.+-- @+-- 'Dict' :: 'Dict' ('Eq' 'Int')+-- @ --+-- captures a dictionary that proves we have an:+--+-- @+-- instance 'Eq' 'Int+-- @+-- -- Pattern matching on the 'Dict' constructor will bring this instance into scope. -- data Dict :: Constraint -> * where@@ -123,13 +133,14 @@ -- Because @'Eq' a@ is a superclass of @'Ord' a@, we can show that @'Ord' a@ -- entails @'Eq' a@. ----- Because @instance 'Ord' a => 'Ord' [a]@ exists, we can show that @'Ord a'@+-- Because @instance 'Ord' a => 'Ord' [a]@ exists, we can show that @'Ord' a@ -- entails @'Ord' [a]@ as well. ----- This relationship is captured in the ':-' entailment type.+-- This relationship is captured in the ':-' entailment type here. -- -- Since @p ':-' p@ and entailment composes, ':-' forms the arrows of a 'Category'--- of constraints.+-- of constraints. However, 'Category' only because sufficiently general to support this+-- instance in GHC 7.8, so prior to 7.8 this instance is unavailable. -- -- But due to the coherence of instance resolution in Haskell, this 'Category' -- has some very interesting properties. Notably, in the absence of@@ -138,17 +149,29 @@ -- arrow. -- -- This means that for instance, even though there are two ways to derive--- @'Ord' a ':-' 'Eq' a@, the answers from these two paths _must_ by+-- @'Ord' a ':-' 'Eq' [a]@, the answers from these two paths _must_ by -- construction be equal. This is a property that Haskell offers that is -- pretty much unique in the space of languages with things they call \"type -- classes\". ----- What are the two ways? Well, we can go from @'Ord' a ':-' 'Eq' a@ via the+-- What are the two ways?+--+-- Well, we can go from @'Ord' a ':-' 'Eq' a@ via the -- superclass relationship, and them from @'Eq' a ':-' 'Eq' [a]@ via the -- instance, or we can go from @'Ord' a ':-' 'Ord' [a]@ via the instance--- then from @'Ord' [a] ':-' 'Eq' [a]'@ through the superclass relationship+-- then from @'Ord' [a] ':-' 'Eq' [a]@ through the superclass relationship -- and this diagram by definition must \"commute\". --+-- Diagrammatically,+--+-- > Ord a+-- > ins / \ cls+-- > v v+-- > Ord [a] Eq a+-- > cls \ / ins+-- > v v+-- > Eq [a]+-- -- This safety net ensures that pretty much anything you can write with this -- library is sensible and can't break any assumptions on the behalf of -- library authors.@@ -158,7 +181,8 @@ type role (:-) nominal nominal --- TODO: _proper_ Data for (p :- q) requires (:-) to be cartesian closed.+-- 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)@@ -205,13 +229,13 @@ -- | Transitivity of entailment ----- If we view '(:-)' as a Constraint-indexed category, then this is '(.)'+-- If we view @(':-')@ as a Constraint-indexed category, then this is @('.')@ trans :: (b :- c) -> (a :- b) -> a :- c trans f g = Sub $ Dict \\ f \\ g -- | Reflexivity of entailment ----- If we view '(:-)' as a Constraint-indexed category, then this is 'id'+-- If we view @(':-')@ as a Constraint-indexed category, then this is 'id' refl :: a :- a refl = Sub Dict @@ -302,6 +326,10 @@ type role Dict nominal +--------------------------------------------------------------------------------+-- Reflection+--------------------------------------------------------------------------------+ -- | Reify the relationship between a class and its superclass constraints as a class -- -- Given a definition such as@@ -337,11 +365,8 @@ class b :=> h | h -> b where ins :: b :- h --------------------------------------------------------------------------------- -- Bootstrapping--------------------------------------------------------------------------------- - instance Class () (Class b a) where cls = Sub Dict instance Class () (b :=> a) where cls = Sub Dict @@ -351,9 +376,7 @@ instance Class () () where cls = Sub Dict instance () :=> () where ins = Sub Dict --------------------------------------------------------------------------------- -- Local, Prelude, Applicative, C.M.I and Data.Monoid instances--------------------------------------------------------------------------------- -- Eq instance Class () (Eq a) where cls = Sub Dict@@ -389,6 +412,7 @@ instance () :=> Ord (Dict a) where ins = Sub Dict instance () :=> Ord (a :- b) where ins = Sub Dict +-- Show instance Class () (Show a) where cls = Sub Dict instance () :=> Show () where ins = Sub Dict instance () :=> Show Bool where ins = Sub Dict@@ -403,6 +427,7 @@ instance () :=> Show (Dict a) where ins = Sub Dict instance () :=> Show (a :- b) where ins = Sub Dict +-- Read instance Class () (Read a) where cls = Sub Dict instance () :=> Read () where ins = Sub Dict instance () :=> Read Bool where ins = Sub Dict@@ -415,6 +440,7 @@ instance (Read a, Read b) :=> Read (Either a b) where ins = Sub Dict instance (Integral a, Read a) :=> Read (Ratio a) where ins = Sub Dict +-- Enum instance Class () (Enum a) where cls = Sub Dict instance () :=> Enum () where ins = Sub Dict instance () :=> Enum Bool where ins = Sub Dict@@ -426,6 +452,7 @@ instance () :=> Enum Double where ins = Sub Dict instance Integral a :=> Enum (Ratio a) where ins = Sub Dict +-- Bounded instance Class () (Bounded a) where cls = Sub Dict instance () :=> Bounded () where ins = Sub Dict instance () :=> Bounded Ordering where ins = Sub Dict@@ -434,6 +461,7 @@ instance () :=> Bounded Char where ins = Sub Dict instance (Bounded a, Bounded b) :=> Bounded (a,b) where ins = Sub Dict +-- Num instance Class () (Num a) where cls = Sub Dict instance () :=> Num Int where ins = Sub Dict instance () :=> Num Integer where ins = Sub Dict@@ -442,6 +470,7 @@ instance RealFloat a :=> Num (Complex a) where ins = Sub Dict instance Integral a :=> Num (Ratio a) where ins = Sub Dict +-- Real instance Class (Num a, Ord a) (Real a) where cls = Sub Dict instance () :=> Real Int where ins = Sub Dict instance () :=> Real Integer where ins = Sub Dict@@ -449,30 +478,36 @@ instance () :=> Real Double where ins = Sub Dict instance Integral a :=> Real (Ratio a) where ins = Sub Dict +-- 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 +-- Fractional instance Class (Num a) (Fractional a) where cls = Sub Dict instance () :=> Fractional Float where ins = Sub Dict 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 +-- 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 +-- 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 +-- 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 +-- Monoid instance Class () (Monoid a) where cls = Sub Dict instance () :=> Monoid () where ins = Sub Dict instance () :=> Monoid Ordering where ins = Sub Dict@@ -480,6 +515,7 @@ instance Monoid a :=> Monoid (Maybe a) where ins = Sub Dict instance (Monoid a, Monoid b) :=> Monoid (a, b) where ins = Sub Dict +-- Functor instance Class () (Functor f) where cls = Sub Dict instance () :=> Functor [] where ins = Sub Dict instance () :=> Functor Maybe where ins = Sub Dict@@ -489,6 +525,7 @@ instance () :=> Functor IO where ins = Sub Dict instance Monad m :=> Functor (WrappedMonad m) where ins = Sub Dict +-- Applicative instance Class (Functor f) (Applicative f) where cls = Sub Dict instance () :=> Applicative [] where ins = Sub Dict instance () :=> Applicative Maybe where ins = Sub Dict@@ -498,17 +535,20 @@ instance Monoid a :=> Applicative ((,)a) where ins = Sub Dict instance Monad m :=> Applicative (WrappedMonad m) where ins = Sub Dict +-- Alternative instance Class (Applicative f) (Alternative f) where cls = Sub Dict instance () :=> Alternative [] where ins = Sub Dict instance () :=> Alternative Maybe where ins = Sub Dict instance MonadPlus m :=> Alternative (WrappedMonad m) where ins = Sub Dict +-- Monad instance Class () (Monad f) where cls = Sub Dict instance () :=> Monad [] where ins = Sub Dict instance () :=> Monad ((->) a) where ins = Sub Dict instance () :=> Monad (Either a) where ins = Sub Dict instance () :=> Monad IO where ins = Sub Dict +-- MonadPlus instance Class (Monad f) (MonadPlus f) where cls = Sub Dict instance () :=> MonadPlus [] where ins = Sub Dict instance () :=> MonadPlus Maybe where ins = Sub Dict
Data/Constraint/Forall.hs view
@@ -20,6 +20,7 @@ -- Stability : experimental -- Portability : non-portable --+-- This module uses a trick to provide quantification over constraints. ---------------------------------------------------------------------------- module Data.Constraint.Forall
constraints.cabal view
@@ -1,6 +1,6 @@ name: constraints category: Constraints-version: 0.4.1+version: 0.4.1.1 license: BSD3 cabal-version: >= 1.10 license-file: LICENSE