[vector] Remove generics from Vector.Shape

[Paul Sandoz]

Hi,

The generics of Vector are a little awkward, stemming from Vector.Shape:

  public interface Vector<E, S extends Vector.Shape<Vector<?, ?>>> {

    interface Species<E, S extends Vector.Shape<Vector<?, ?>>> {

    interface Mask<E, S extends Shape<Vector<?, ?>>> {

    interface Shuffle<E, S extends Shape<Vector<?, ?>>> {

    interface Shape<V extends Vector<?, ?> /*extends Vector<?, Shape<V>>*/> {


It's not clear to me why Shape needs to have any type variable which is bound to Vector. 

- There are no methods on Shape that depend on Vector.

- We cannot bind more specific shapes types to only be applicable to more specific vector types.

- Factory methods should be responsible for obtaining a Species given a Class and Shape. It’s a runtime query as to whether a combination of the class and shape can produce a required Species from which Vector instances can be created. (Same applies to casting/resizing/reshaping).

Therefore i propose:

  public interface Vector<E, S extends Vector.Shape> {

    interface Species<E, S extends Vector.Shape> {

    interface Mask<E, S extends Shape> {

    interface Shuffle<E, S extends Shape> {

    interface Shape {


Methods accepting or returning Vector/Species etc generic in shape then become less imposing e.g.:

-    static <E, S extends Vector.Shape<Vector<?, ?>>> Vector.Species<E, S> speciesInstance(Class<E> c, S s) {
+    static <E, S extends Vector.Shape> Vector.Species<E, S> speciesInstance(Class<E> c, S s) {
         Vector.Species<E, S> res = null;

-        Vector.Species<?, Vector.Shape<Vector<?, ?>>> species =
+        Vector.Species<?, Vector.Shape> species =
                 Vector.preferredSpeciesInstance(box);

-    static <S extends Vector.Shape<Vector<?, ?>>> int mismatch(byte[] a, byte[] b, ByteVector.ByteSpecies<S> species) {
+    static <S extends Vector.Shape> int mismatch(byte[] a, byte[] b, ByteVector.ByteSpecies<S> species) {

Paul.