Consider four kinds of "arrow" symbols: 0. A horizontal line 1. A leftarrow 2. A rightarrow 3. A doublearrow
I'd like to add circles to each end of these arrows, allowing for all possible combinations of "filled" and "unfilled," for a total of sixteen combinations in total. As an example, one may consider the "spoons" offered by the MnSymbol package for reference, as in
Any ideas as to how to achieve this?
EDIT: So to clarify, I want circles on BOTH ends of the arrows. As in O-->O.