
Drake's AutoDiff implementation
-------------------------------

This directory is a work-in-progress for Drake's forthcoming replacement of
`Eigen::AutoDiffScalar<Eigen::VectorXd>`.

The `namespace ad { ... }` is chosen for it's compact size in debugging traces,
but is not otherwise exposed to users.

Users should continue to `#include <drake/common/autodiff.h>` and refer to
`drake::AutoDiffXd` in their code.

Once we are confident with our replacement implementation, we will switch that
alias to refer to this new code instead of Eigen's AutoDiffScalar.
