Portability	portable
Stability	experimental
Maintainer	forsyde-dev@ict.kth.se

ForSyDe.AbsentExt

Description

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

Synopsis

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

Typeable1 AbstExt
Eq a => Eq (AbstExt a)
Data a => Data (AbstExt a)
Read a => Read (AbstExt a)
Show a => Show (AbstExt a)	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'.
Lift a[a7JAe] => Lift (AbstExt a[a7JAe])
ProcType a => ProcType (AbstExt a)

fromAbstExt Source

Arguments

:: a	Default value returned if the input is `Abst`
-> AbstExt a
-> a

The function fromAbstExt extracts the inner value contained in AbstExt

unsafeFromAbstExt :: AbstExt a -> aSource

Similar to fromAbstExt, but without default value

abstExt :: a -> AbstExt aSource

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

psi :: (a -> b) -> AbstExt a -> AbstExt bSource

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 bSource

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