The function raise(con_met, A, 2, 3) computes the tensor A with indices 2 and 3 raised using the contravariant metric con_met.

The function lower(cov_met, A, 1, 4) computes the tensor A with indices 1 and 4 lowered using the covariant metric cov_met.

Each index in the call to raise must be a valid covariant index of A.

Each index in the call to lower must be a valid contravariant index of A.

There must be at least 1 index given and the number of indices cannot exceed the rank of A.

Simplification:  These routines use the `tensor/prod/simp` routine for simplification purposes.  The simplification routine is applied to each component of the result after it is computed.  By default, `tensor/prod/simp` is initialized to the `tensor/simp` routine. It is recommended that the `tensor/prod/simp` routine be customized to suit the needs of the particular problem.

These functions are part of the tensor package, and so can be used in the form raise(..) / lower(..) only after performing the command with(tensor), or with(tensor, raise) / with(tensor, lower).  These functions can always be accessed in the long form tensor[raise](..) / tensor[lower](..).