if I have a Memb defined as:

Memb<Particles> particles

can i get the index to a member of the Memb by passing in a Particles object?

the memb header shows this...
Int index (TYPE *elm){return _Memb::index (elm);

which would lead me to expect:

Particles p;
int i = particles.find(&p);

to work.. but that is causing errors...

Thanks!

Memb::find compares the values (like Particle==Particle)
you should use Memb::index

but I pass a pointer to the element?

yes, Memb::index requires the elements address, and then it checks if the container has an element of that address