[GRASS-dev] Re: [GRASS GIS] #73: r.out.gdal tiff output does not work

[Glynn Clements]

Markus Metz wrote:

> >    - all floating point: IEEE's NaN
> 
> Problem with NaN? According to IEEE 754, x == y is always FALSE if 
> either x or y or both are NaN. Assuming (nodata = 
> GDALGetRasterNoDataValue()) == NaN, then going through all cells if 
> (cell == nodata) will always be FALSE, nodata cells may not be detected? 
> Depends on each implementation of nodata detection? Can be solved for 
> GRASS, but how is this done in all other GIS applications?

	if (x == nodata || isnan(nodata) && isnan(x))

isnan() is C99 and POSIX, or it can be defined as e.g.:

	#define ISNAN(x) ((x) != (x))

-- 
Glynn Clements <glynn at gclements.plus.com>