what does this code mean? Help
 

DEFINE_UDS_FLUX(MyFlux,f,t,i)
{
real NV_VEC(unit_vec), NV_VEC(A);
F_AREA(A, f, t);
NV_DS(unit_vec, =, 1, 1, 1, *, 1);
return NV_DOT(unit_vec, A);
}
NV_VEC and NV_DS are both new to me. I can't find them in udf help?
Can someone tell me and what does the code above mean?

NV_VEC(u)
==
u[ND_ND]

NV_DS(u, =, 1, 1, 1, *, 2)
=>
u = [1,1,1]*2 = [2,2,2] (interpretation, not code)

Thanks you for your response.I get the two NV macro.And could you tell what does the code meaning? The UDS is new to me. Thanks a lot