Copyright	(c) Andrey Mulik 2020-2021
License	BSD-style
Maintainer	work.a.mulik@gmail.com
Portability	non-portable (GHC extensions)
Safe Haskell	Trustworthy
Language	Haskell2010

SDP.Nullable

Contents

Nullable
- Rank 2 quantified constraints
- Patterns

Description

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

Synopsis

class Nullable e where
- lzero :: e
- isNull :: e -> Bool
type Nullable1 rep e = Nullable (rep e)
type Nullable2 rep i e = Nullable (rep i e)
type Nullable' rep = forall e. Nullable (rep e)
type Nullable'' rep = forall i e. Nullable (rep i e)
pattern NULL :: Nullable e => e
pattern Z :: Nullable e => e

Nullable

class Nullable e where Source #

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 Source #

Empty value.

default lzero :: Monoid e => e Source #

isNull :: e -> Bool Source #

Is value empty?

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

Instances

Instances details

Nullable E Source #	Since: 0.2.1
Instance details Defined in SDP.Finite Methods lzero :: E Source # isNull :: E -> Bool Source #
Nullable [e] Source #
Instance details Defined in SDP.Nullable Methods lzero :: [e] Source # isNull :: [e] -> Bool Source #
Nullable (Maybe e) Source #
Instance details Defined in SDP.Nullable Methods lzero :: Maybe e Source # isNull :: Maybe e -> Bool Source #
Nullable (StablePtr e) Source #
Instance details Defined in SDP.Nullable Methods lzero :: StablePtr e Source # isNull :: StablePtr e -> Bool Source #
Nullable (Ptr e) Source #
Instance details Defined in SDP.Nullable Methods lzero :: Ptr e Source # isNull :: Ptr e -> Bool Source #
Nullable (FunPtr e) Source #	Since: 0.2.1
Instance details Defined in SDP.Nullable Methods lzero :: FunPtr e Source # isNull :: FunPtr e -> Bool Source #
Nullable (ForeignPtr e) Source #
Instance details Defined in SDP.Nullable Methods lzero :: ForeignPtr e Source # isNull :: ForeignPtr e -> Bool Source #
Nullable (SBytes# e) Source #
Instance details Defined in SDP.Prim.SBytes Methods lzero :: SBytes# e Source # isNull :: SBytes# e -> Bool Source #
Nullable (SArray# e) Source #
Instance details Defined in SDP.Prim.SArray Methods lzero :: SArray# e Source # isNull :: SArray# e -> Bool Source #
Nullable (TArray# e) Source #
Instance details Defined in SDP.Prim.TArray Methods lzero :: TArray# e Source # isNull :: TArray# e -> Bool Source #
Index i => Nullable (i, i) Source #
Instance details Defined in SDP.Index Methods lzero :: (i, i) Source # isNull :: (i, i) -> Bool Source #
Nullable (AnyChunks rep e) Source #
Instance details Defined in SDP.Templates.AnyChunks Methods lzero :: AnyChunks rep e Source # isNull :: AnyChunks rep e -> Bool Source #
(Index i, Bordered (rep e) Int, Nullable (rep e)) => Nullable (AnyBorder rep i e) Source #
Instance details Defined in SDP.Templates.AnyBorder Methods lzero :: AnyBorder rep i e Source # isNull :: AnyBorder rep i e -> Bool Source #

type Nullable1 rep e = Nullable (rep e) Source #

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

Since: 0.2.1

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

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) Source #

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

Since: 0.2.1

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

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

Since: 0.2.1

Patterns

pattern NULL :: Nullable e => e Source #

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

pattern Z :: Nullable e => e Source #

Other empty value pattern: Z === NULL.

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