I can add a bool return value.  I just don't understand what it is supposed to mean.  It doesn't mean IK failed to find a solution.  The RobotState may still be changed even if it returns false (right?).  I guess my real problem is that I do not understand the meaning of the value returned from RobotState::setFromIK().

The whole purpose of this class is to call this function.  Making it private would defeat the purpose (every user of the struct would have to be a friend).

However, I think I actually do not call this from modifyState -- there is an intermediate function -- so I can probably change this to use references.  Will look at that...