SDP.Nullable

SDP.Nullable provides Nullable - class of types with empty values.

Nullable

class Nullable e where

Nullable is class of types which have empty values.

Nullable instances must follow some rules:

   isNull Z === True
   x == Z ==> isNull x == True
   x == y === isNull x == isNull y
   
   -- For Foldable instances
   toList Z === []
   fold   Z === mempty
   isNull x === null x
   isNull x === length x == 0
   
   sum      Z === 0
   product  Z === 1
   elem   x Z === False
   foldr  f Z === foldl  f Z === id
   foldr1 f Z === foldl1 f Z === undefined
 

Minimal complete definition

Nothing

Methods

lzero :: e

Empty value.

default lzero :: Monoid e => e

isNull :: e -> Bool

Is value empty?

default isNull :: Eq e => e -> Bool

Instances

Nullable E

Since: 0.2.1

Defined in SDP.Finite

Methods

lzero :: E

isNull :: E -> Bool

Nullable [e]

Defined in SDP.Nullable

Methods

lzero :: [e]

isNull :: [e] -> Bool

Nullable (Maybe e)

Defined in SDP.Nullable

Methods

lzero :: Maybe e

isNull :: Maybe e -> Bool

Nullable (StablePtr e)

Defined in SDP.Nullable

Methods

lzero :: StablePtr e

isNull :: StablePtr e -> Bool

Nullable (Ptr e)

Defined in SDP.Nullable

Methods

lzero :: Ptr e

isNull :: Ptr e -> Bool

Nullable (FunPtr e)

Since: 0.2.1

Defined in SDP.Nullable

Methods

lzero :: FunPtr e

isNull :: FunPtr e -> Bool

Nullable (ForeignPtr e)

Defined in SDP.Nullable

Methods

lzero :: ForeignPtr e

isNull :: ForeignPtr e -> Bool

Nullable (SBytes# e)

Defined in SDP.Prim.SBytes

Methods

lzero :: SBytes# e

isNull :: SBytes# e -> Bool

Nullable (SArray# e)

Defined in SDP.Prim.SArray

Methods

lzero :: SArray# e

isNull :: SArray# e -> Bool

Nullable (TArray# e)

Defined in SDP.Prim.TArray

Methods

lzero :: TArray# e

isNull :: TArray# e -> Bool

Index i => Nullable (i, i)

Defined in SDP.Index

Methods

lzero :: (i, i)

isNull :: (i, i) -> Bool

Nullable (AnyChunks rep e)

Defined in SDP.Templates.AnyChunks

Methods

lzero :: AnyChunks rep e

isNull :: AnyChunks rep e -> Bool

(Index i, Bordered (rep e) Int, Nullable (rep e)) => Nullable (AnyBorder rep i e)

Defined in SDP.Templates.AnyBorder

Methods

lzero :: AnyBorder rep i e

isNull :: AnyBorder rep i e -> Bool

type Nullable1 rep e = Nullable (rep e)

Nullable contraint for (Type -> Type)-kind types.

Since: 0.2.1

type Nullable2 rep i e = Nullable (rep i e)

Nullable contraint for (Type -> Type -> Type)-kind types.

Since: 0.2.1

Rank 2 quantified constraints

GHC 8.6.1+ only

type Nullable' rep = forall e. Nullable (rep e)

Nullable contraint for (Type -> Type)-kind types.

Since: 0.2.1

type Nullable'' rep = forall i e. Nullable (rep i e)

Nullable contraint for (Type -> Type -> Type)-kind types.

Since: 0.2.1

Patterns

pattern NULL :: Nullable e => e

Originally defined in sdp-ctypes (now sdp-foreign), same as Z now.

pattern Z :: Nullable e => e

Other empty value pattern: Z === NULL.

Defined in SDP.Nullable since sdp-0.2.1, earlier - in SDP.Linear.