Problem with method Plus in the Vector class

[marco turchi]

Dear All,
I have a strange behaviour when I use the method Plus for Vector.

I have a RandomAccessSparseVector vector, if I add a positive number, I got
a new Vector where each element is the sum of the old value plus the
positive number. While if I add a negative number, the new vector has 1 more
entry:


RandomAccessSparseVector distV = new RandomAccessSparseVector(1);
distV.setQuick(0,1);
double mean = 1;
RandomAccessSparseVector app =
(RandomAccessSparseVector)(distV.plus(mean));

the output is
{0:2.0}

if I have
double mean = -1;
RandomAccessSparseVector app =
(RandomAccessSparseVector)(distV.plus(mean));

the output is
{1:1.0,0:-1.0}

For sure I'm doing something wrong. Do you have any ideas where the problem
is?

Thanks a lot in advance
Marco