[Gretl-devel] Re: exists() vs. inbundle()
Am 19.04.20 um 17:06 schrieb Allin Cottrell:
On Wed, 8 Apr 2020, Sven Schreiber wrote:
> I know that currently where inbundle(b, "m") returns 0 because m isn't
> there, exists(b.m) instead yields an error. But I guess that could be
> changed if wanted.
> And vice versa: inbundle(a, "x") yields an error if there is no bundle
> a, whereas exists(a.x) just returns 0. But are those differences really
> by design or just by historical coincidence?
Good points. There's some redundancy here (particularly if we throw in
typeof() as well).
Ah I hadn't even thought of typeof().
* However, exists(b.m) should be non-committal, so should return 0 if
either b doesn't exist or it doesn't have anything under the key "m".
That's now fixed in git.
OK, good.
As for exists() vs typeof() -- they're basically the same thing under
two names: the same back-end, and exists() returns the same codes as
typeof(), though the help text is a little coy about that!
Perhaps exists() should just be documented as an alias.
Yes, probably. I guess it
wouldn't hurt to be explicit in the
documentation about the construction 'if exists()' without checking the
return code in detail.
Now talking of typeof(): it returns numeric type codes, which
typestr() can "translate". Not all that convenient. We recently
introduced the symbolic constants TRUE and FALSE. Would it be overkill
to introduce a few more: NULL, SCALAR, SERIES, MATRIX, STRING, BUNDLE,
ARRAY? In that case you could do things like
if typeof(b.m) == MATRIX
Spontaneously I'm not sure if that's necessary. OTOH if something like
that is done I think it should go all the way and also differentiate
different types of arrays. Maybe typeof() could just accept an optional
second string literal argument which then triggers such an equality check:
if typeof(b.m, "matrix") # returns 1 if b.m is a matrix
or:
typeof(bb, "bundles") # checks if bb is an array of bundles
cheers
sven