Copyright	(c) ForSyDe Group KTH 2007-2008
License	BSD-style (see the file LICENSE)
Maintainer	forsyde-dev@ict.kth.se
Stability	experimental
Portability	portable
Safe Haskell	Safe
Language	Haskell98

ForSyDe.Shallow.Core.AbsentExt

Description

The AbstExt is used to extend existing data types with the value 'absent', which models the absence of a value.

Synopsis

data AbstExt a
- = Abst
- | Prst a
fromAbstExt :: a -> AbstExt a -> a
abstExt :: a -> AbstExt a
psi :: (a -> b) -> AbstExt a -> AbstExt b
isAbsent :: AbstExt a -> Bool
isPresent :: AbstExt a -> Bool
abstExtFunc :: (a -> b) -> AbstExt a -> AbstExt b

Documentation

data AbstExt a Source #

The data type AbstExt has two constructors. The constructor Abst is used to model the absence of a value, while the constructor Prst is used to model present values.

Constructors

Abst
Prst a

Instances

Functor AbstExt Source #
Instance details Defined in ForSyDe.Shallow.Core.AbsentExt Methods fmap :: (a -> b) -> AbstExt a -> AbstExt b # (<$) :: a -> AbstExt b -> AbstExt a #
Eq a => Eq (AbstExt a) Source #
Instance details Defined in ForSyDe.Shallow.Core.AbsentExt Methods (==) :: AbstExt a -> AbstExt a -> Bool # (/=) :: AbstExt a -> AbstExt a -> Bool #
Read a => Read (AbstExt a) Source #
Instance details Defined in ForSyDe.Shallow.Core.AbsentExt Methods readsPrec :: Int -> ReadS (AbstExt a) # readList :: ReadS [AbstExt a] # readPrec :: ReadPrec (AbstExt a) # readListPrec :: ReadPrec [AbstExt a] #
Show a => Show (AbstExt a) Source #	The data type `AbstExt` is defined as an instance of `Show` and `Read`. '_' represents the value `Abst` while a present value is represented with its value, e.g. `Prst` 1 is represented as '1'.
Instance details Defined in ForSyDe.Shallow.Core.AbsentExt Methods showsPrec :: Int -> AbstExt a -> ShowS # show :: AbstExt a -> String # showList :: [AbstExt a] -> ShowS #

fromAbstExt :: a -> AbstExt a -> a Source #

The function fromAbstExt converts a value from a extended value.

abstExt :: a -> AbstExt a Source #

The function abstExt converts a usual value to a present value.

psi :: (a -> b) -> AbstExt a -> AbstExt b Source #

The function psi is identical to abstExtFunc and should be used in future.

isAbsent :: AbstExt a -> Bool Source #

The functions isAbsent checks for the absence of a value.

isPresent :: AbstExt a -> Bool Source #

The functions isPresent checks for the presence of a value.

abstExtFunc :: (a -> b) -> AbstExt a -> AbstExt b Source #

The function abstExtFunc extends a function in order to process absent extended values. If the input is ("bottom"), the output will also be ("bottom").