[GiNaC-list] ex thread safe?

[Zhao Li]

We are trying to implement the GiNaC calculation in multi-thread by using functor,
	auto func = [](void)->void {…};
However we found that (pointer) problem arises if the arguments are passed by reference. 
	auto func = [&](void)->void {…};
But it seems okay to pass by value.
	auto func = [=](void)->void {…};
We were wondering if it is really okay to pass by value, or we have to transfer GiNaC::ex into string as argument. And we do not understand why passing by reference is not okay.

Cheers,
Zhao