Intervalar Mathematics with Octave

[Oscar]

I'm developing a work in which I would like to create a benchmark that
focus in accuracy more than speed for floating point operations. For
the test case I will use some polynomials evaluation methods. My
problem is that, in order to check the quality of the answer, I would
have to check the answer with a "faithful result", this is where
Octave would come in.
I need a interval mathematic to use with octave, does it exist?
Also, I would need to use some C++ code, is it possible in Octave? Can
I Call octave functions from a C++ code or use some DLL in the Octave?

Thank you,
Oscar Albrecht