Just -package:relational-record

Runs a Maybe generator until it produces a Just. This is implemented using filter and has the same caveats.

Analogous to Just and equivalent to return

Analogous to Just, promotes a value of type typ into one of type Maybe typ. It should hold that val . Just === just . val. This function will try not to produce a nested Maybe. This is in accord with how SQL represents NULL. That means that just . just = just. This behavior was changed in v3.6.0.0. If you want to produce nested Maybe, see just'.

A prism on the Just element of a Maybe.

just :: Prism (Maybe a) (Maybe b) a b

A prism on the Just element of a Maybe.

Cast record phantom type into Maybe.

Cast into Maybe on record phantom type.

Assert that some value is Just.

A predicate checking if the input is Just, wrapping a value matching the given predicate.

>>> Just 1 `shouldSatisfy` P.just (P.gt 0)

The Just constructor lifted over the Expr type. This works for the Bool, Int, Char argument types and their lists.

> just zero
Just 0 :: Maybe Int
> just false
Just False :: Maybe Bool

A Predicate that accepts Maybe values of Just x, where x matches the given child Predicate.

>>> accept (just (eq "value")) Nothing
False

>>> accept (just (eq "value")) (Just "value")
True

>>> accept (just (eq "value")) (Just "wrong value")
False

TMap which contains only one entry from the empty string to a.

Justification for label and maybe other widgets (text?)