A text generator that generates a string that matches a regular expression.

    
    import qualified Test.QuickCheck as QC
    import Test.QuickCheck.StringRandom (matchRegexp)

    prop_generateDigit :: QC.Property
    prop_generateDigit = QC.forAll (matchRegexp "\d") $ digit -> ...

    -- or

    newtype Upper = Upper Text.Text deriving (Eq, Show)

    instance QC.Arbitrary Upper where
      arbitrary = Upper $ matchRegexp "[A-Z]"

    prop_generateUpper :: Upper -> Bool
    prop_generateUpper (Upper upper) = ...

The shrink function has not been defined yet.