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From: =?utf-8?Q?Arne_Pl=C3=B6se_=28JIRA=29?= <jira@apache.org>
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Subject: [jira] [Commented] (MATH-571) make FieldVector generic
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    [ https://issues.apache.org/jira/browse/MATH-571?page=3Dcom.atlassian.j=
ira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D130313=
60#comment-13031360 ]=20

Arne Pl=C3=B6se commented on MATH-571:
---------------------------------

Maybe this code works ... Yes it looks ugly ...

I want to extend FieldElement and wnt it use in vector and matrix.
=20
so the problem is getting the right "backing class" for the interface.
For the matrix is a third generics needed....

Maybe someone has a better solution here is my "draft".

public class App=20
{
    public static interface FieldElement<T> {

        T add(T a);
    }

    public static interface FieldVector<T extends FieldElement<T>, V extend=
s FieldVector> {

        V multiply(FieldVector<T, ?> v);

        V createVector(T[] data);

    }

    public static interface ComplexFieldElement<T extends ComplexFieldEleme=
nt<T>> extends FieldElement<T> {

        double getReal();

        T conjugate();
    }

    public static class Complex implements ComplexFieldElement<Complex> {

        @Override
        public double getReal() {
            return 1;
        }

        @Override
        public Complex add(Complex a) {
            return new Complex();
        }

        @Override
        public Complex conjugate() {
            throw new UnsupportedOperationException("Not supported yet.");
        }
    }

    public static interface GenericComplexFieldVector<T extends ComplexFiel=
dElement<T>, V extends GenericComplexFieldVector> extends FieldVector<T, V>=
 {

        V conjugate();

        double[] getReal();
    }

    public abstract static class AbstractArrayFieldVector<T extends FieldEl=
ement<T>, V extends FieldVector> implements FieldVector<T, V> {

        protected T[] data;

        @Override
        public V multiply(FieldVector<T, ?> v) {
            return createVector(data);
        }
    }

    public static class ArrayFieldVector<T extends FieldElement<T>> extends=
 AbstractArrayFieldVector<T, FieldVector> {

        @Override
        public ArrayFieldVector createVector(T[] data) {
            ArrayFieldVector result =3D new ArrayFieldVector();
            result.data =3D data;
            return result;
        }
    }

    public abstract static class AbstractArrayComplexVector<T extends Compl=
exFieldElement<T>, V extends GenericComplexFieldVector> extends AbstractArr=
ayFieldVector<T, V> implements GenericComplexFieldVector<T, V>{

        @Override
        public double[] getReal() {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        @Override
        public V conjugate() {
            throw new UnsupportedOperationException("Not supported yet.");
        }

    }

    public static interface ComplexVector extends GenericComplexFieldVector=
<Complex, ComplexVector> {

    }

    public static class ArrayComplexVector extends AbstractArrayComplexVect=
or<Complex, ComplexVector> implements ComplexVector {

        @Override
        public ComplexVector createVector(Complex[] data) {
            ArrayComplexVector result =3D new ArrayComplexVector();
            result.data =3D data;
            return (ComplexVector)result;
        }


    }

public static void main(String [] args) {
        ArrayComplexVector v =3D new ArrayComplexVector();
        ComplexVector v1 =3D v.multiply(new ArrayComplexVector());  // File=
dVector type survives ...
        FieldVector<Complex, ?> v2 =3D v1.multiply(v);
        FieldVector<Complex, FieldVector> v3 =3D v2.multiply(v2);
    }
}


> make FieldVector generic
> ------------------------
>
>                 Key: MATH-571
>                 URL: https://issues.apache.org/jira/browse/MATH-571
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 3.0
>            Reporter: Arne Pl=C3=B6se
>            Priority: Minor
>
> make FieldVector generic, so one can extend i.e. ArrayVieldVector<Complex=
> to ArrayComplexVector an introduce new methoids (getReal())...
> if one has an equation complexvector.copy the original type ArrayComplexV=
ector is lost thus access to getReal() is not possible.
> solution:
> public class InheritationTest {
>     public static interface FieldVector<T extends FieldElement<T>, R exte=
nds FieldVector> {
>         R copy();
>     }
>     public abstract static class ArrayFieldVectorExtendable<T extends Fie=
ldElement<T>, R extends FieldVector> implements FieldVector<T, R>, Serializ=
able {
>         protected T[] data;
>         @Override
>         public R copy() {
>             return createVector(data);
>         }
>         abstract protected R createVector(T[] data);
>     }
>     public static class ArrayFieldVector<T extends FieldElement<T>> exten=
ds ArrayFieldVectorExtendable<T, ArrayFieldVector> {
>         @Override
>         protected ArrayFieldVector<T> createVector(T[] data) {
>             ArrayFieldVector<T> result =3D new ArrayFieldVector<T>();
>             result.data =3D data;
>             return result;
>         }
>     }
>     public static class ArrayComplexVector extends ArrayFieldVectorExtend=
able<Complex, ArrayComplexVector> {
>         @Override
>         protected ArrayComplexVector createVector(Complex[] data) {
>             ArrayComplexVector result =3D new ArrayComplexVector();
>             result.data =3D data;
>             return result;
>         }
>         public double[] getReal() {
>             return null;
>         }
>         public double[] getImaginary() {
>             return null;
>         }
>     }
>     public void test() {
>         ArrayComplexVector v =3D new ArrayComplexVector();
>         ArrayComplexVector v1 =3D v.copy();  // FiledVector type survives=
 ...
>     }
> }

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