httk.atomistic.symmetry.xyz
===========================

.. py:module:: httk.atomistic.symmetry.xyz

.. autoapi-nested-parse::

   Exact parsers for crystallographic coordinate-operation notation.



Functions
---------

.. autoapisummary::

   httk.atomistic.symmetry.xyz.parse_linear_expression
   httk.atomistic.symmetry.xyz.operation_from_xyz
   httk.atomistic.symmetry.xyz.operation_from_xyzt


Module Contents
---------------

.. py:function:: parse_linear_expression(expression, allowed_vars = _SUPERSPACE_VARS)

   Parse one superspace linear expression into integer coefficients and a translation.

   The parser accepts the six superspace variables ``x1`` through ``x6`` by default and
   preserves an exact rational translation.

   :param expression: The linear expression to parse.
   :param allowed_vars: The variable names accepted in ``expression``.
   :return: The integer coefficients in ``allowed_vars`` and the exact translation.
   :raises ValueError: If the expression is empty, malformed, or has a non-integer
       variable coefficient.


.. py:function:: operation_from_xyz(operation)

   Parse an exact three-coordinate crystallographic operation.

   :param operation: The comma-separated ``x,y,z`` operation string.
   :return: The exact affine operation.
   :raises ValueError: If the operation does not contain three valid coordinate
       expressions.


.. py:function:: operation_from_xyzt(operation)

   Parse an exact magnetic operation and return its time-reversal flag.

   The first three comma-separated fields use crystallographic ``x,y,z`` grammar; the
   fourth field must be ``+1`` or ``-1``.

   :param operation: The comma-separated ``x,y,z,time-reversal`` operation string.
   :return: The affine operation and its time-reversal sign.
   :raises ValueError: If the operation does not contain three coordinate expressions and
       a valid time-reversal flag.