Re: [Gretl-devel] Backward compatibility

On Mon, 5 Nov 2007, Ignacio Diaz-Emparanza wrote: > I suppose you remember my message about building a function > with one input series and several output series, that I wanted > to be named accordingly to the input series (see > http://lists.wfu.edu/pipermail/gretl-users/2007-June/001722.html > ). > > I needed a "string" parameter in a function, but given that > string parameters are not allowed in a function I solved my > problem using an external string inside my function (I know > this is not very smart but ... ). I agree wholeheartedly on the fact that it should be possible to use strings as function arguments. Every time I tried to write complex user-level sets of functions, this limitation was quite painful.

The issue is not easy, though. From my understanding of the code, it works more or less like this (Allin, please correct me where I'm wrong -- it could be ALL wrong): every user-defined string is contained in a static array called saved_strings; as such, no matter how deep function nesting is, all strings are potentially accessible. However, we keep track of the level at which each string is defined, so that the string is in fact usable only at that level.

We could work around Ignacio's problem in more than one way: 1) let strings be visible everywhere. Definitely dangerous.

4) enable GRETL_TYPE_STRING as a function argument and store a copy of the string in the global array, only marked at a different level. The copy should be destroyed on function exit.