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Special values
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NA values
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All OBITypes have an associated NA (Not Available) value. 
NA values are implemented by specifying an explicit NA value for each type, corresponding to the R standards:

* For the types ``OBIInt_t``, ``OBIBool_t``, ``OBIIdx_t`` and ``OBITaxid_t``, the NA value is ``INT_MIN``.

* For the type ``OBIChar_t``: the NA value is ``\0`` (?).

* For the type ``OBIStr_t`` : the NA value is ``\0`` (?).

* For the type ``OBIFloat_t``::

    typedef union
    {
        double value;
        unsigned int word[2];
    } ieee_double;
    
    static double NA_value(void)
    {
        volatile ieee_double x;
        x.word[hw] = 0x7ff00000;
        x.word[lw] = 1954;
        return x.value;
    }   


Minimum and maximum values for ``OBIInt_t``
===========================================

* Maximum value : ``INT_MAX``
* Minimum value : ``INT_MIN(-1?)``


Infinity values for the type ``OBIFloat_t``
===========================================

* Positive infinity : ``INFINITY`` (should be defined in ``<math.h>``)
* Negative infinity : ``-INFINITY``


NaN value for the type ``OBIFloat_t``
=====================================

* NaN (Not a Number) value : ``NAN`` (should be defined in ``<math.h>`` but probably needs to be tested)