[GRASS-dev] How to: if undefined, set to NULL?

[Nikos Alexandris]

While modifying i.rgb.his,

    if (chroma == 0.0) {

        saturation = 0.0;

        /* undefined -- (how to) set to NULL? */
        hue = 0.0;

        rowbuffer[0][sample] = (FCELL)hue;
        rowbuffer[1][sample] = (FCELL)intensity;
        rowbuffer[2][sample] = (FCELL)saturation;
    }


I'd like to set hue to NULL, whenever the condition is met. How do I do that?

    hue = NULL;

does not work.

Thanks for any help, Nikos