> (define-class Foo
    x y z)
> (define-class-instance foo Bar
    1 2 3)
. define-class-instance: expected class in: Bar
> (define-class-instance foo Foo
    1 2)
. define-class-instance: need 3 arguments in: (define-class-instance foo Foo 1 2)
> (define-class-instance foo Foo
    1 2 3)
> (slot-value bar n)
. slot-value: expected typed id in: bar
> (slot-value foo n)
. slot-value: slot n does not exist in class Foo. in: (slot-value foo n)
> (slot-value foo y)
2
>