[GRASS-dev] lib fn to convert int color number to RGB values?

[Glynn Clements]

Ivan Shmakov wrote:

>  >>> if (color <= 0) return 0;
> 
>  >> BTW, is it a GRASS convention to use 0 to indicate failure?
>  >> Standard C library functions tend to use -1 for failure, while using
>  >> non-negative values to indicate success.
> 
>  > The SUBMITTING file in the source code says:
> 
>  > 8.  Exit status is defined as EXIT_SUCCESS or EXIT_FAILURE, e.g.
> 
>  > {
>  >     ...
>  >     if (G_parser (argc, argv))
>  >         exit (EXIT_FAILURE);
> 
>  >     ...
>  >     exit (EXIT_SUCCESS);
>  > }
> 
>  > AFAIU, these are defined in stlib as being respectively 0 and 1.
> 
> 	Yes.  But the conventions for the exit code of a program are
> 	hardly applicable to the return value of a function.
> 
> 	Consider, e. g. (from ``The GNU C Library Reference Manual''):
> 
> --cut: (libc) Opening and Closing Files--
>  -- Function: int open (const char *FILENAME, int FLAGS[, mode_t MODE])

> --cut: (libc) Process Group Functions--
>  -- Function: int setpgid (pid_t PID, pid_t PGID)

Those functions return a meaningful non-negative integer upon success. 
GRASS functions which behave likewise normally return -1 for failure,
but functions which only return success or failure use C logic values,
with zero (false) for failure and non-zero (true) for success.

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