optional

To avoid null errors Angle offers the swift way

class car{
 name:string // default
 name:string! // required
 year:date? //optional
}

Fields can be made required in function declarations via with keyword or nested schemas:

age of car with year = car.year
age of car{year} = car.year

The scheme of the type can be deep: arrival time of package{destination{address{zip or street}}} = calculate distance to zip …

make optionally as unknown default but enable way to specify the requirement of fields:

to get movie time of user with name and zip:...
to place order for user with last name and address:...

Julia style

movie-time (user:{name, address: zip} ) = ...

Nested optionality thanks to Rick Hickey from closure

These required attributes can also be inferred from the compiler:

peter{last-name=fox zip=1234}
movie-time(peter) // compiler warning/error: movie time requires peter to have a name
// extra: did you mean lastname?