Unit ⋅ This ⋅ That ⋅ These ⋅ True ⋅ False ⋅ Alone ⋅ Exist ⋅ Empty ⋅ Maybe ⋅ Error ⋅ Valid ⋅ Stops ⋅ Given ⋅ Event ⋅ State ⋅ Label ⋅ Value ⋅ Impel