[Gretl-devel] matrix declaration in a pakage

[Allin Cottrell]

On Wed, 4 Jul 2007, Ignacio Diaz-Emparanza wrote:

> If you want to use a matrix in a function pakage, the matrix 
> need to be declared previously...

I have just put in place a new Windows snapshot which should 
have better error-reporting for user-defined functions.

As for the issue of "matrix needs to be declared previously", 
there are two cases:

A. The matrix argument is direct or by-value, of type "matrix".  
In this case it is indeed an error if you type a name to which 
there corresponds no pre-existing matrix.  This error should now 
be flagged properly.

B. The matrix argument is indirect or by-reference, of type 
"matrix *".  In this case, if you type a name, and no matrix 
exists of that name, a new "null matrix" [in fact, a 1 x 1 matrix 
with value 0] will be created automatically and supplied as the 
argument in question. 

The point is that in case B it's plausible that the function is 
not interested in the original content of the matrix. but is 
rather offering to re-size and fill the matrix with something that 
might be of interest to the caller.  (Obviously, if you as the 
writer of a function package actually expect valid incoming 
information in such an indirect matrix argument, you'll have to 
check for this.)

I've taken another look at the code, and I don't see anything 
relevant that should differ between Linux and Windows -- though. 
of course, I could have missed some weird subtlety!

Allin.