[Gretl-devel] still some function package editing problems

[Allin Cottrell]

On Fri, 26 Jan 2007, Sven Schreiber wrote:

> 1. package the following example function:
>
> function test(list myl[null])
>  if nelem(myl) != 0
>    print "This shouldn't be printed if the user didn't touch the
> default input."
>  endif
> end function
>
> 2. open some datafile and create an arbitrary but non-empty list named
> "spam"
>
> 3. execute the function package from step 1; list "spam" appears as
> selected in the list input drop-down menu
>
> So the function package does not honor the [null] default setting.
>
> Nothing too serious, but a little annoying.

Thanks, I now see what you mean.

It seems to me: whether this is a problem or not is a bit subtle, 
and depends on the context.  When a function gives a [null] 
default for a list argument, is it saying A or B?

A: "I'd normally expect a list here, but if you don't want to give 
one I can manage without"

B: "A basic invocation of this function wouldn't have a list 
here, but if you want to get fancy you can specify one"

I presume you have case B in mind, but in case A the behaviour you 
describe you not, I think, seem wrong.

Allin.