Why doesn't Java 8's Predicate extend Function

Question

If I wrote the Predicate interface, I\'d want to encode in the interface the fact that it\'s just a function that returns a primitive boolean, like thi

Answer 1

There is no need for such a suspicious inheritance hierarchy. These functional interfaces are inter-changable.

Function f1=…;
Predicate        p1=…;

Predicate        p2=f1::apply;
Function f2=p1::test;

This works in both directions. So why should there be an inheritance relationship advertising one specific direction?