validity 0.3.0.2 → 0.3.0.3

raw patch · 3 files changed

+79/−27 lines, 3 filesdep ~base

Dependency ranges changed: base

Files

• src/Data/RelativeValidity.hs +5/−2
• src/Data/Validity.hs +71/−22
• validity.cabal +3/−3

@@ -1,11 +1,12 @@-{-# LANGUAGE FlexibleInstances #-}+{-# LANGUAGE FlexibleInstances     #-} {-# LANGUAGE MultiParamTypeClasses #-}  {-| Relative validity- -}+    -}  module Data.RelativeValidity     ( RelativeValidity(..)+    , isInvalidFor     ) where  @@ -20,3 +21,5 @@ class RelativeValidity a b where     isValidFor :: a -> b -> Bool +isInvalidFor :: RelativeValidity a b => a -> b -> Bool+isInvalidFor a b = not $ isValidFor a b

@@ -2,42 +2,49 @@  {-| - @Validity@ is used to specify additional invariants upon values that are not- enforced by the type system.+    @Validity@ is used to specify additional invariants upon values that are not+    enforced by the type system. - Let's take an example.- Suppose we were to implement a type @Prime@ that represents prime integers.+    Let's take an example.+    Suppose we were to implement a type @Prime@ that represents prime integers. - If you were to completely enforce the invariant that the represented number is- a prime, then we could use @Numeric.Natural@ and only store the index of the- given prime in the infinite sequence of prime numbers.- This is very safe but also very expensive if we ever want to use the number,- because we would have to calculcate all the prime numbers until that index.+    If you were to completely enforce the invariant that the represented number is+    a prime, then we could use @Numeric.Natural@ and only store the index of the+    given prime in the infinite sequence of prime numbers.+    This is very safe but also very expensive if we ever want to use the number,+    because we would have to calculcate all the prime numbers until that index. - Instead we choose to implement @Prime@ by a @newtype Prime = Prime Int@.- Now we have to maintain the invariant that the @Int@ that we use to represent- the prime is in fact positive and a prime.+    Instead we choose to implement @Prime@ by a @newtype Prime = Prime Int@.+    Now we have to maintain the invariant that the @Int@ that we use to represent+    the prime is in fact positive and a prime. - The @Validity@ typeclass allows us to specify this invariant (and enables- testing via the @genvalidity@ libraries:- https://hackage.haskell.org/package/genvalidity ):+    The @Validity@ typeclass allows us to specify this invariant (and enables+    testing via the @genvalidity@ libraries:+    https://hackage.haskell.org/package/genvalidity ): - > instance Validity Prime where- >     isValid (Prime n) = isPrime n- -}+    > instance Validity Prime where+    >     isValid (Prime n) = isPrime n+    -}  module Data.Validity     ( Validity(..)+    , isInvalid     , constructValid     , constructValidUnsafe     ) where +import           Data.Maybe (fromMaybe) + -- | A class of types that have additional invariants defined upon them -- that aren't enforced by the type system class Validity a where+    -- | Check whether a given value is a valid value.     isValid :: a -> Bool +isInvalid :: Validity a => a -> Bool+isInvalid = not . isValid+ -- | Any tuple of things is valid if both of its elements are valid instance (Validity a, Validity b) => Validity (a, b) where     isValid (a, b) = isValid a && isValid b@@ -62,7 +69,52 @@     isValid Nothing = True     isValid (Just a) = isValid a +-- | Trivially valid+instance Validity () where+    isValid = const True +-- | Trivially valid+instance Validity Bool where+    isValid = const True++-- | Trivially valid+instance Validity Ordering where+    isValid = const True++-- | Trivially valid+instance Validity Char where+    isValid = const True++-- | Trivially valid+instance Validity Int where+    isValid = const True++-- | Trivially valid+instance Validity Word where+    isValid = const True++-- | NOT trivially valid:+--+-- * NaN is not valid.+-- * Infinite values are not valid.+instance Validity Float where+    isValid d+      =  not (isNaN d)+      && not (isInfinite d)++-- | NOT trivially valid:+--+-- * NaN is not valid.+-- * Infinite values are not valid.+instance Validity Double where+    isValid d+      =  not (isNaN d)+      && not (isInfinite d)++-- | Trivially valid+instance Validity Integer where+    isValid = const True+ -- | Construct a valid element from an unchecked element constructValid :: Validity a => a -> Maybe a constructValid p = if isValid p then Just p else Nothing@@ -70,8 +122,5 @@ -- | Construct a valid element from an unchecked element, throwing 'error' -- on invalid elements. constructValidUnsafe :: (Show a, Validity a) => a -> a-constructValidUnsafe p =-    case constructValid p of-        Nothing -> error $ show p ++ " is not valid"-        Just p -> p+constructValidUnsafe p = fromMaybe (error $ show p ++ " is not valid") $ constructValid p 

@@ -1,11 +1,11 @@ name:                validity-version:             0.3.0.2+version:             0.3.0.3 synopsis:            Validity typeclass-description:        +description:   Note: There are companion instance packages for this library:   .   * <https://hackage.haskell.org/package/validity-text validity-text>-  .                                                 +  .   * <https://hackage.haskell.org/package/validity-containers validity-containers>  homepage:            https://github.com/NorfairKing/validity#readme