[Gretl-devel] members of lists returned from functions

[Allin Cottrell]

On Tue, 12 Feb 2008, Sven Schreiber wrote:

> I have thought about it a little bit but could only think of a 
> solution for the builtin functions like the ones you're talking 
> about: names starting with 'l_' and the like could be made 
> "semi-reserved" in the manual, explaining that you risk losing 
> them.
> 
> But IMHO the situation is totally different for user-defined 
> functions: users should not be required to do a risk analysis or 
> thoroughly study the documentation of a function before playing 
> around with it. 

Just thinking out loud, but here's one possibility: whenever a 
function returns a list (I think that's the only case we're 
talking about) there's an automatically accepted final string 
argument, namely the "basename" for variables in the returned 
list, which then (say) get consecutive numeric suffixes.

For example, consider

function foo (series x, int opt)
  ...
  return list xlist
end function

If you called foo as

  list mylist = foo(myvar, 4, "myname")

then gretl would intercept the list at return time and name its 
members as myname1, myname2 and so on, before they're shifted into 
caller space.

One could get fancier by allowing a more flexible naming template 
as the extra argument, rather than just a prefix, but that's the 
basic idea.

Allin.