ForSyDe.AbsentExt

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

Documentation

data AbstExt a

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[a8cpC] => Lift (AbstExt a[a8cpC])

ProcType a => ProcType (AbstExt a)

fromAbstExt

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 -> a

Similar to fromAbstExt, but without default value

abstExt :: a -> AbstExt a

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

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

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

isAbsent :: AbstExt a -> Bool

The functions isAbsent checks for the absence of a value.

isPresent :: AbstExt a -> Bool

The functions isPresent checks for the presence of a value.

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

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