On Tue, Feb 26, 2008 at 5:25 PM, Maciej Sieczka <[EMAIL PROTECTED]> wrote: > Glynn Clements pisze: > > > -2^31 (= 0x80000000 = -2147483648) is the null value > > for the CELL type, so you'll never see that value in a map. > > > The FP nulls are the all-ones bit patterns. These corresponds to NaN > > according to the IEEE-754 formats, although it isn't the "default" NaN > > pattern generated by most architectures (which is usually 7fc00000 or > > ffc00000 for float and 7ff8000000000000 or fff8000000000000 for > > double, i.e. an all-ones exponent, the top-bit of the mantissa set, > > and either sign). > > > > So far as arithmetic is concerned, any value with an all-ones exponent > > and a non-zero mantissa is treated as NaN. But the GRASS > > G_is_[fd]_null_value() functions only consider the all-ones bit > > pattern to be null. I intend to change this in 7.x so that all FP NaN > > values are treated as null. This will mean that code which can > > generate NaNs doesn't have to explicitly convert them to the GRASS > > null value. > > These should go to "Raster data processing in GRASS GIS". As I don't > really understand the part about floating point, I won't do it myself. > Somebody more savvy please do, putting it some simpler words if possible.
Added like this as http://trac.osgeo.org/grass/changeset/30458 Feel free to improve... Markus _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
