Syntax
=====

.. code-block:: text

    mater_field = AFFE_MATERIAU (
        ◆ | MESH = mesh,
          | MODEL = model,
        ◆/AFFE = _F (
               ◆/TOUT = "OUI" (or not specified),
                 /GROUP_MA = grma,
               ◆ MATER = subdue,
            ),
          /CHAM_MATER = mater_field,
        ◇ AFFE_COMPOR = _F (
             ◆/TOUT = "OUI" (or not specified),
               /GROUP_MA = grma,
             ◆ COMPOR = compor,
          ),
        ◇ AFFE_VARC = _F (
             ◇/TOUT = "OUI" (or not specified),
               /GROUP_MA = grma,
             ◆ NOM_VARC =/"TEMP ",
                          /"GEOM ",
                          /"CORR ",
                          /"IRRA ",
                          /"HYDR ",
                          /"SECH ",
                          /"EPSA ",
                          /"M_ ACIER ",
                          /"M_ ZIRC ",
                          /"NEUT1 ",
                          /"NEUT2 ",
                          /"NEUT3 ",
                          /"PTOT ",
             ◆/CHAM_GD = cham_gd,
               /EVOL = evol,
             # If: exists (" EVOL ")
                 ◇ NOM_CHAM =/"TEMP ",
                              /"CORR ",
                              /"IRRA ",
                              /"NEUT ",
                              /"GEOM ",
                              /"HYDR_ELNO ",
                              /"HYDR_NOEU ",
                              /"META_ELNO ",
                              /"META_NOEU ",
                              /"EPSA_ELNO ",
                              /"EPSA_NOEU ",
                              /"PTOT ",
                              /"HHO_TEMP ",
                 ◇ PROL_DROITE =/"CONSTANT ",
                                 /"LINEAIRE ",
                                 /"EXCLU" (by default),
                 ◇ PROL_GAUCHE =/"CONSTANT ",
                                 /"LINEAIRE ",
                                 /"EXCLU" (by default),
                 ◇ FONC_INST = formula/function,
             # If: is_in (" NOM_VARC ", ('TEMP', 'SECH'))
                 ◆ VALE_REF = float,
          ),
        ◇ INFO =/1 (by default),
                 /2,
    )
    
    ◆: mandatory
    ◇: optional
    : present by default
    &: together
    /: only one among
    |: several possible choices