# Source code for MDAnalysis.selections.gromacs

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    # R. J. Gowers, M. Linke, J. Barnoud, T. J. E. Reddy, M. N. Melo, S. L. Seyler,
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    # J. Comput. Chem. 32 (2011), 2319--2327, doi:10.1002/jcc.21787
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    """
    Gromacs selections
    ==================

    Write :class:`MDAnalysis.core.groups.AtomGroup` selection to a `ndx`_ file
    that defines a Gromacs_ index group. To be used in Gromacs like this::

      <GROMACS_COMMAND> -n macro.ndx

    The index groups are named *mdanalysis001*, *mdanalysis002*, etc.

    .. _Gromacs: http://www.gromacs.org
    .. _ndx: https://manual.gromacs.org/current/reference-manual/file-formats.html#ndx

    .. autoclass:: SelectionWriter
       :inherited-members:
    """
    from . import base

    class SelectionWriter(base.SelectionWriterBase):
        format = ["Gromacs", "ndx"]
        ext = "ndx"
        default_numterms = 12

        def _translate(self, atoms, **kwargs):
            # Gromacs index is 1-based; MDAnalysis is 0-based
            return [str(atom.index + 1) for atom in atoms]

        def _write_head(self, out, **kwargs):
            out.write("[ {name!s} ]\n".format(**kwargs))