In a previous question I asked Why can the Monad interface not be declared in Java?. There, I received a comment from Brian Goetz saying that I should have called "higher order types" "higher kinded types".
Now, I read more about type systems and I understand the concept of higher kinded types. However, I am still confused by the terms. I tried to disambiguate them by myself using Google, however there does not seem to be a clear answer. Thus, my question is what is the exact meaning of the following terms:
Do all three terms exist? Is there a difference between them? What is the difference? Does the meaning vary between programming languages?
I also noticed that StackOverflow has multiple tags:
However, there is no tag wiki for both of them.
Following this blog post, the term higher order type seems to be the common term for higher kinded type and higher rank type. higher order kind is probably a term that I just made up when I was confused.
With higher kinded types, it is possible to receive a type parameter that itself is a generic type:
interface Foo<T<_>> {
T<String> get();
}
This is what is necessary to declare the Monad interface.
With higher rank types, it is possible to receive a parameter whose type still contains unspecified type parameters:
interface Bar {
void foobar(<E> List<E> list);
}
Unfortunately, higher rank type checking/inference is undecidable.