Defines absolute (no-arg) predicate construct. Predicate like closure is a first-class function
that is defined with (or closed over) its free variables that are bound to the closure
scope at execution.
To provide for more terse code you can use a typedef
P1 class or various factory methods in
GridFunc class. Note, however, that since typedefs in Java rely on inheritance you should
not use these type aliases in signatures.
Note that this interface does not impose or assume any specific thread-safety by its
implementations. Each implementation can elect what type of thread-safety it provides,
if any.