Accessing a constant

Question

Why can\'t I access \'B\' in the following from \'A\' but can from the main environment?

module A; end
A.instance_eval{B=1}

B #=> 1
A::B #=> uninitial         


        

Answer 1

module A; end
A.class_eval{B=1}
B # Undefined
A::B # 1

As for why it works, I'm not really sure. I occasionally use metaprogramming like this when creating very meta frameworks such the Small Eigen Collider, but not in day-to-day work.