Constants
~~~~~~~~~

.. tab:: Python

  The following mathematical and physical constants are available through the ``n`` module: 

  .. list-table:: Mathematical and Physical Constants
      :header-rows: 1

      * - Constant
        - Value
        - Description
      * - ``n.PI``
        - 3.14159265358979323846
        - 
      * - ``n.E``
        - 2.71828182845904523536
        - 
      * - ``n.GAMMA``
        - 0.57721566490153286060
        - Euler's constant
      * - ``n.DEG``
        - 57.29577951308232087680
        - Degrees per radian
      * - ``n.PHI``
        - 1.61803398874989484820
        - Golden ratio
      * - ``n.FARADAY``
        - 96485.3321233100141
        - Modern value, derived from mole and electron charge
      * - ``n.R``
        - 8.3144626181532395
        - Modern value, derived from Boltzmann constant and mole
      * - ``n.Avogadro_constant``
        - 6.02214076e23
        - CODATA 2018 value, introduced in version 8.0

  As of Version 8.0 (circa October, 2020) modern units are the default.

  .. warning::
      Constants are not treated specially by the interpreter and 
      may be changed with assignment statements. However a change of
      ``FARADAY``, ``R``, or ``Avogadro_constant`` generates a warning message
      (default once).
      Python warning messages can be managed with
      ``import warnings; warnings.filterwarnings(action)`` where useful actions
      are ``"error"``, ``"ignore"``, ``"always"``, or ``"once"``.
      If assignment takes
      place due to execution of a hoc interpreter statement, the warning occurs
      only once but cannot be avoided.

.. tab:: HOC

  The following mathematical and physical constants are built-in to the HOC interpreter: 

  .. list-table:: Mathematical and Physical Constants
      :header-rows: 1

      * - Constant
        - Value
        - Description
      * - ``PI``
        - 3.14159265358979323846
        - 
      * - ``E``
        - 2.71828182845904523536
        - 
      * - ``GAMMA``
        - 0.57721566490153286060
        - Euler's constant
      * - ``DEG``
        - 57.29577951308232087680
        - Degrees per radian
      * - ``PHI``
        - 1.61803398874989484820
        - Golden ratio
      * - ``FARADAY``
        - 96485.3321233100141
        - Modern value, derived from mole and electron charge
      * - ``R``
        - 8.3144626181532395
        - Modern value, derived from Boltzmann constant and mole
      * - ``Avogadro_constant``
        - 6.02214076e23
        - CODATA 2018 value, introduced in version 8.0

  As of Version 8.0 (circa October, 2020) modern units are the default.

  .. note::

    By default, HOC displays less digits of precision than shown here.

  .. warning::
      Constants are not treated specially by the interpreter and 
      may be changed with assignment statements. However a change of
      ``FARADAY``, ``R``, or ``Avogadro_constant`` generates a warning message
      (default once).
      Python warning messages can be managed with
      ``import warnings; warnings.filterwarnings(action)`` where useful actions
      are ``"error"``, ``"ignore"``, ``"always"``, or ``"once"``.
      If assignment takes
      place due to execution of a hoc interpreter statement, the warning occurs
      only once but cannot be avoided.

.. tab:: MATLAB

  The following mathematical and physical constants are available through the ``n`` object
  (where ``n = neuron.launch()``): 

  .. list-table:: Mathematical and Physical Constants
      :header-rows: 1

      * - Constant
        - Value
        - Description
      * - ``n.PI``
        - 3.14159265358979323846
        - 
      * - ``n.E``
        - 2.71828182845904523536
        - 
      * - ``n.GAMMA``
        - 0.57721566490153286060
        - Euler's constant
      * - ``n.DEG``
        - 57.29577951308232087680
        - Degrees per radian
      * - ``n.PHI``
        - 1.61803398874989484820
        - Golden ratio
      * - ``n.FARADAY``
        - 96485.3321233100141
        - Modern value, derived from mole and electron charge
      * - ``n.R``
        - 8.3144626181532395
        - Modern value, derived from Boltzmann constant and mole
      * - ``n.Avogadro_constant``
        - 6.02214076e23
        - CODATA 2018 value, introduced in version 8.0

  As of Version 8.0 (circa October, 2020) modern units are the default.

  .. warning::
      Constants are not treated specially by the interpreter and 
      may be changed with assignment statements. However a change of
      ``FARADAY``, ``R``, or ``Avogadro_constant`` generates a warning message
      (default once).
      Python warning messages can be managed with
      ``import warnings; warnings.filterwarnings(action)`` where useful actions
      are ``"error"``, ``"ignore"``, ``"always"``, or ``"once"``.
      If assignment takes
      place due to execution of a hoc interpreter statement, the warning occurs
      only once but cannot be avoided.