Ions
====



.. function:: ion_style


    Syntax:
        ``oldstyle = h.ion_style("name_ion", c_style, e_style, einit, eadvance, cinit, sec=section)``

        ``oldstyle = h.ion_style("name_ion", sec=section)``


    Description:
        In the ``section``, 
        force the named ion (eg. na_ion, k_ion, ca_ion, etc) to handle 
        reversal potential and concentrations according to the indicated 
        styles. 
        You will not often need this function since the 
        style chosen automatically on a per section basis should be 
        appropriate to the set of mechanisms inserted in each section. 
         
        Warning: if other mechanisms are inserted subsequent to a call 
        of this function, the style will be "promoted" according to 
        the rules associated with adding the used ions to the style 
        previously in effect. 
         
        The oldstyle value is previous internal setting of 
        c_style + 4*cinit +  8*e_style + 32*einit + 64*eadvance. 
         


        c_style: 0, 1, 2, 3. 
            Concentrations respectively treated as UNUSED, 
            PARAMETER, ASSIGNED, or STATE variables.  Determines which panel (if 
            any) will show the concentrations. 

        e_style: 0, 1, 2, 3. 
            Reversal potential respectively treated as 
            UNUSED, PARAMETER, ASSIGNED, or STATE variable. 

        einit: 0 or 1. 
            If 1 then reversal potential computed by Nernst equation 
            on call to :func:`finitialize` using values of concentrations. 

        eadvance: 0 or 1. 
            If 1 then reversal potential computed every call to 
            :func:`fadvance` using the values of the concentrations. 

        cinit: 0 or 1. 
            If 1 then a call to finitialize() sets the concentrations 
            to the values of the global initial concentrations. eg. ``nai`` set to 
            ``h.nai0_na_ion`` and ``nao`` set to ``h.nao0_na_ion``. 

         
        The automatic style is chosen based on how the set of mechanisms that 
        have been inserted in a section use the ion. Note that the precedence is 
        WRITE > READ > unused in the USEION statement; so if one mechanism 
        READ's  cai/cao and another mechanism WRITE's them then WRITE takes precedence 
        in the following table. For compactness, the table assumes the ca ion. 
        Each table entry identifies the equivalent parameters to the ion_style 
        function. 

            ==========    =========   =========   =========
            cai/cao ->    unused      read        write 
            ==========    =========   =========   =========
            eca unused    0,0,0,0,0   1,0,0,0,0   3,0,0,0,1 
            eca read      0,1,0,0,0   1,2,1,0,0   3,2,1,1,1 
            eca write     0,2,0,0,0   1,2,0,0,0   3,2,0,0,1 
            ==========    =========   =========   =========

        For example suppose one has inserted a mechanism that READ's eca, 
        a mechanism that READ's cai, cao and a mechanism that WRITE's cai, cao 
        Then, since WRITE takes precedence over READ in the above table, 
        ``cai/cao`` would appear in the STATE variable panel (first arg is 3), 
        ``eca`` would appear in the ASSIGNED variable panel (second arg is 2), 
        ``eca`` would be calculated on a call to finitialize (third arg is 1), 
        ``eca`` would be calculated on every call to fadvance (fourth arg is 1), 
        ``cai/cao`` would be initialized (on finitialize) to the global variables 
        ``cai0_ca_ion`` and ``cao0_ca_ion`` respectively. (note that this takes place just 
        before the calculation of ``eca``). 



----



.. function:: ion_register


    Syntax:
        ``type = h.ion_register("name", charge)``


    Description:
        Create a new ion type with mechanism name, "name_ion", and associated 
        variables: iname, nameo, namei, ename, diname_dv. 
        If any of these names already 
        exists and name_ion is not already an ion, the function returns -1, 
        otherwise it returns the mechanism type index. If name_ion is already 
        an ion the charge is ignored but the type index is returned. 


----



.. function:: ion_charge


    Syntax:
        ``charge = h.ion_charge("name_ion")``


    Description:
        Return the charge for the indicated ion mechanism. An error message is 
        printed if name_ion is not an ion mechanism.