[GRASS-dev] Some doubts

[Glynn Clements]

Roberto Antolin wrote:

> I have some questions that I would like to resolve.
> 
> This summer I was discussing with Markus about extern variables. He told 
> me that there were some compilation problems and it would be better not 
> to use them. But I saw that they are used all over GRASS. So, which is 
> the point with them? Should they be declare in an especial way?

Ideally, you should structure your code so as to minimise the need for
variables to be exported. Beyond that, exported variables should avoid
"trivial" names, as they are more likely to conflict.

If a module is particularly complex and requires a significant number
of variables to be visible throughout the module, it might be worth
encapsulating them into a structure to minimise the number of exported
symbols.

> There is a second question about the database and driver module's 
> options. When I wrote my modules (v.surf.bspline, v.outlier and 
> v.lidar.*) I needed the database and driver information. I decide to ask 
> the user for them in the case he/she wants to use other than the default 
> values. But, is better to ask the user for these parameters within the 
> module, or maybe is better to use the default values?

The user should set the database parameters using db.connect. There
shouldn't be any reason for individual modules to use anything other
than the current database.

> A third final question: To show the progress of the module, is actually 
> needed?

It depends upon typical execution times. If a module might take more
than a few seconds, and deriving an estimate of completion is
straightforward, it's a good idea to use G_percent() to indicate
progress.

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