  To simulate open boundaries within finite computation domain, real-function
coordinate transformation in the framework of generally covariant formulation
of Maxwell equations is proposed. The mapping--realized with arctangent
function here--has a transparent geometric meaning of pure squeezing of space,
is admissible by classical electrodynamics, does not introduce artificially
lossy layers (or `lossy coordinates') to absorb outgoing radiation nor leads to
non-Maxwellian fields. At the same time, like for anisotropic perfectly matched
layers, no modification (except for transformation of material tensors) is
needed to existing nearest-neighbor computation schemes, which makes it well
suited for parallel computing implementation.
