Syntax
=====

.. code-block:: text

    interspectrum = PROJ_SPEC_BASE (
        ◆ SPEC_TURB = spectrum,
        ◇ TOUT_CMP =/"OUI" (by default),
                     /"NON ",
        ◆/BASE_ELAS_FLUI = melasflu,
          /MODE_MECA = meca fashion,
          /CHAM_NO = fiel_no,
        # If: exists (" BASE_ELAS_FLUI ")
            ◆ VITE_FLUI = float,
            ◇ PRECISION = float (default: 0.001),
        ◆ FREQ_INIT = float,
        ◆ FREQ_FIN = float,
        ◆ NB_POIN = int,
        ◇ OPTION =/"TOUT" (by default),
                   /"DIAG ",
        ◆/TOUT = "OUI" (or not specified),
          /GROUP_MA = grma,
        ◇ & MODELE_INTERFACE = model,
        ◇ VECT_X = float,
        ◇ VECT_Y = float,
        ◇ ORIG_AXE = float,
        ◇ TITRE = text,
    )
    
    ◆: mandatory
    ◇: optional
    : present by default
    &: together
    /: only one among
    |: several possible choices