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Syntax conventions
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The following syntax rules apply throughout this manual:

- Lowercase letters (e.g. xyz) denote an input variable or other parameters;
- Uppercase letters (e.g. XYZ) denote a keyword or a predefined argument value;
- Anything enclosed in ``[ .. ]`` is optional, meaning it is not mandatory;
- ``( .. | .. )`` means the user must choose one of the possibilities separated by the ``|`` character.

Example for ``X [B]``

.. code-block:: m6geo

  X B   * Valid: use option B
  X     * Valid: do not use option
  X C   * Not valid: does not match the option



These two syntax notations can be combined to any degree of complexity.
For example, the syntax ``X (A | [B])`` means the user must choose between A, B, or nothing:

.. code-block:: m6geo

  X A   * Choose first option A
  X B   * Choose second option B
  X     * Select nothing, since option B is not mandatory