public interface Lazy<T>
Promise, but
Future also implements Lazy.
Primitive operations (such as arithmetic) require non-lazy (or "eager") values;
in Kawa these are automatically evaluated ("forced")
using Promise.force(java.lang.Object) or equivalent.
In Kawa all objects are considered eager (non-lazy) unless the
object's class implements Lazy, though note that an eager value
may contain lazy components (for example an eager vector of lazy values).
Note that the compiler assumes that Promise.force(java.lang.Object) is a no-op and
does not need to be emitted unless the type of the value implements
Lazy, or the class is Object.
(See LazyType.maybeLazy(gnu.bytecode.Type).)
T getValue()
getValue() may return this,
if this object isn't actually lazy.
It may also return another lazy value.
Normally you should use Promise.force{val}
to extra a non-lazy (eager) value.