public ColumnsStore(final MatrixStore<N> aBase, final int... someColumns) {
super((int) aBase.countRows(), someColumns.length, aBase);
myColumns = someColumns;
myFirst = 0;
}
public ColumnsStore(final int aFirst, final int aLimit, final MatrixStore<N> aBase) {
super((int) aBase.countRows(), aLimit - aFirst, aBase);
myColumns = null;
myFirst = aFirst;
}