[GRASS-dev] CELL/FCELL/DCELL [was: Re: r.mapcal rand() strangeness]

[Glynn Clements]

Hamish wrote:

> > Below follow details about CELL and DCELL datatypes in GRASS. It
> > would be good to have them summarrised in GRASS raster intro IMHO;
> > + FCELL specific notes. 
> ...
> > >>> A double has a precision of ~16 decimal digits, which matches
> > >>> what you see above.
> 
> 
> this stuff seems (to me) a bit too technical for the short "hello
> raster" intro pages. is there another place we could put it?

	http://en.wikipedia.org/wiki/Floating-point
	http://en.wikipedia.org/wiki/IEEE_754

> libgis Doxygen comments -> the (under advertised) programmer's manual?
> maybe that is too far away from the user..?

It doesn't belong in the programmer's manual any more than tutorials
on the C language or the Unix API do.

FWIW, the help file for Windows' calc.exe doesn't explain it either.

> to take the idea further, when do you end describing how binary
> computers deal with storing non-binary numbers? sure explain what GRASS
> has used and the limits that imposes, maybe on a wiki page with links
> to wikipedia articles on the general gotchas of modern C, x86,
> endianness, etc. which may be natural to a computer scientist but
> foriegn to an ecologist expecting a number to be number?

Where do you stop? Do we include tutorials on using bash (or cmd.exe
for Windows users), Unix filesystem permissions, grep/sed/awk (those
are useful for processing input and output to/from various GRASS
commands), statistics, ...?

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