[GRASS-dev] patch for v.voronoi/v.delaunay

[Markus Neteler]

On Sat, May 3, 2008 at 5:33 AM, Hamish <hamish_b at yahoo.com> wrote:
> Markus Neteler wrote:
>  > It seems that the precision gets somewhere lost in
>  > db_convert_column_value_to_string()
>  >
>  > i.e. lib/db/dbmi_base/columnfmt.c
>  >
>  > but I don't find where is is rounded.
>
>
>  lib/db/dbmi_base/valuefmt.c db_convert_value_to_string() does:
>         case DB_C_TYPE_DOUBLE:
>             sprintf (buf, "%lf",db_get_value_double(value));
>             G_trim_decimal(buf);
>
>  the %lf is rounding to %.6f?
>
>  maybe
>  - "%lf"
>  + "%.14f"
>
>  then let G_trim_decimal() remove any extra .00000s.
>
>  but maybe such noisy output is not always wanted. :-/

Let's do the fix because a library should keep the precision.
We can reduce noise in the modules then.

>  (e.g. pretty output for d.what.vect tcl form)
>  ?

Yes, but trim that at module level.

>  FWIW v.out.ascii defaults to dp=8.

So we should consequently use the same length everywhere
(adjustable) and full precision at library level.

>  for the v.colors script, SQL  "select * WHERE dbl_col = <FP number>" is
>  always going to be problematic.
>
>  the C way:
>   if( abs(test - value) < GRASS_EPSILON )


On Sat, May 3, 2008 at 7:41 AM, Hamish <hamish_b at yahoo.com> wrote:
>  In the case of v.colors, the SQL set loop could be rewritten to avoid
>  this problem by matching to the cat number, not trying to logically match
>  the FP value.

This would be good.

Markus