Data.Express.Instances

Defines utilities do deal with instances of typeclasses

Functions provided by this module store the set of instances as a simple Haskell list. When storing only a few instances this should be fine in terms of performance.

If you plan to store hundreds or thousands of instances, we recommend implementing different versions that use a more efficient Set/Map storage.

Documentation

reifyEq :: (Typeable a, Eq a) => a -> [Expr]

O(1). Reifies an Eq instance into a list of Exprs. The list will contain == and /= for the given type. (cf. mkEq, mkEquation)

> reifyEq (undefined :: Int)
[ (==) :: Int -> Int -> Bool
, (/=) :: Int -> Int -> Bool ]

> reifyEq (undefined :: Bool)
[ (==) :: Bool -> Bool -> Bool
, (/=) :: Bool -> Bool -> Bool ]

> reifyEq (undefined :: String)
[ (==) :: [Char] -> [Char] -> Bool
, (/=) :: [Char] -> [Char] -> Bool ]

reifyOrd :: (Typeable a, Ord a) => a -> [Expr]

O(1). Reifies an Ord instance into a list of Exprs. The list will contain compare, <= and < for the given type. (cf. mkOrd, mkOrdLessEqual, mkComparisonLE, mkComparisonLT)

> reifyOrd (undefined :: Int)
[ (<=) :: Int -> Int -> Bool
, (<) :: Int -> Int -> Bool ]

> reifyOrd (undefined :: Bool)
[ (<=) :: Bool -> Bool -> Bool
, (<) :: Bool -> Bool -> Bool ]

> reifyOrd (undefined :: [Bool])
[ (<=) :: [Bool] -> [Bool] -> Bool
, (<) :: [Bool] -> [Bool] -> Bool ]

reifyEqOrd :: (Typeable a, Ord a) => a -> [Expr]

O(1). Reifies Eq and Ord instances into a list of Expr.

reifyName :: (Typeable a, Name a) => a -> [Expr]

O(1). Reifies a Name instance into a list of Exprs. The list will contain name for the given type. (cf. mkName, lookupName, lookupNames)

> reifyName (undefined :: Int)
[name :: Int -> [Char]]

> reifyName (undefined :: Bool)
[name :: Bool -> [Char]]

mkEq :: Typeable a => (a -> a -> Bool) -> [Expr]

O(1). Builds a reified Eq instance from the given == function. (cf. reifyEq)

> mkEq ((==) :: Int -> Int -> Bool)
[ (==) :: Int -> Int -> Bool
, (/=) :: Int -> Int -> Bool ]

mkOrd :: Typeable a => (a -> a -> Ordering) -> [Expr]

O(1). Builds a reified Ord instance from the given compare function. (cf. reifyOrd, mkOrdLessEqual)

mkOrdLessEqual :: Typeable a => (a -> a -> Bool) -> [Expr]

O(1). Builds a reified Ord instance from the given <= function. (cf. reifyOrd, mkOrd)

mkName :: Typeable a => (a -> String) -> [Expr]

O(1). Builds a reified Name instance from the given name function. (cf. reifyName, mkNameWith)

mkNameWith :: Typeable a => String -> a -> [Expr]

O(1). Builds a reified Name instance from the given String and type. (cf. reifyName, mkName)

isEq :: [Expr] -> Expr -> Bool

O(n+m). Returns whether an Eq instance exists in the given instances list for the given Expr.

> isEq (reifyEqOrd (undefined :: Int)) (val (0::Int))
True

> isEq (reifyEqOrd (undefined :: Int)) (val ([[[0::Int]]]))
False

Given that the instances list has length m and that the given Expr has size n, this function is O(n+m).

isOrd :: [Expr] -> Expr -> Bool

O(n+m). Returns whether an Ord instance exists in the given instances list for the given Expr.

> isOrd (reifyEqOrd (undefined :: Int)) (val (0::Int))
True

> isOrd (reifyEqOrd (undefined :: Int)) (val ([[[0::Int]]]))
False

Given that the instances list has length m and that the given Expr has size n, this function is O(n+m).

isEqOrd :: [Expr] -> Expr -> Bool

O(n+m). Returns whether both Eq and Ord instance exist in the given list for the given Expr.

Given that the instances list has length m and that the given Expr has size n, this function is O(n+m).

isEqT :: [Expr] -> TypeRep -> Bool

O(n). Returns whether an Eq instance exists in the given instances list for the given TypeRep.

> isEqT (reifyEqOrd (undefined :: Int)) (typeOf (undefined :: Int))
True

> isEqT (reifyEqOrd (undefined :: Int)) (typeOf (undefined :: [[[Int]]]))
False

Given that the instances list has length n, this function is O(n).

isOrdT :: [Expr] -> TypeRep -> Bool

O(n). Returns whether an Ord instance exists in the given instances list for the given TypeRep.

> isOrdT (reifyEqOrd (undefined :: Int)) (typeOf (undefined :: Int))
True

> isOrdT (reifyEqOrd (undefined :: Int)) (typeOf (undefined :: [[[Int]]]))
False

Given that the instances list has length n, this function is O(n).

isEqOrdT :: [Expr] -> TypeRep -> Bool

O(n). Returns whether both Eq and Ord instance exist in the given list for the given TypeRep.

Given that the instances list has length n, this function is O(n).

mkEquation :: [Expr] -> Expr -> Expr -> Expr

mkComparisonLE :: [Expr] -> Expr -> Expr -> Expr

mkComparisonLT :: [Expr] -> Expr -> Expr -> Expr

mkComparison :: String -> [Expr] -> Expr -> Expr -> Expr

lookupComparison :: String -> TypeRep -> [Expr] -> Maybe Expr

listVarsWith :: [Expr] -> Expr -> [Expr]

lookupName :: [Expr] -> Expr -> String

lookupNames :: [Expr] -> Expr -> [String]

validApps :: [Expr] -> Expr -> [Expr]

findValidApp :: [Expr] -> Expr -> Maybe Expr

preludeNameInstances :: [Expr]