Re: [Gretl-devel] functions optional arguments - numerical (NA equiv. to null), python like syntax (wish)
Am 08.01.2018 um 10:21 schrieb Schaff, Frederik:
Hi there, I pose this question & suggestion here instead the users
list, I hope that is fine in this context.
Yes, perfect.
It is currently not possible to use „null“ as a default argument for
scalar variables in function headers. It is, however, possible to use
„NA“. My question: Is there a save procedure to use “!isnan(variable)”
similar to “exists(matrix)” for function headers? Currently, this
seems not possible (or I am making a mistake). E.g.:
You're making a mistake :-)
NaN is not the same as NA. You can dig up a bunch of discussions about
gretl's creation of NAs in the lists in the past.
But the point for you is that you probably want to use missing() or ok().
Apart from that, I would usually recommend against a NA default value
for a scalar. Instead use a "sensible" default that really is something
that would be chosen often. Or use some code value; for example if a
strictly positive number is expected, the default value 0 can be taken
as an equivalent signal to NA. Or of only non-negative numbers make
sense, use -1 to signal some special meaning. And so on.
And then one other thing. In Python one can conveniently pass optional
arguments via “argument_label=argument_value”, without having to care
about the sorting/completeness of the argument list. If such a thing
was possible in hansl, that would be very convenient!
Yes it would be, and in many other senses Python is much more flexible
than hansl, too. That's why the Python + Numpy + Scipy (+ statsmodels +
pandas and so forth) ecosystem is so successful. But having named
arguments (as opposed to only positional arguments) is of course not a
Python-specific thing. (R also has it, for example.)
Anyway, it would be nice to have, but I'm afraid that it would represent
a major internal reorganization effort. (Allin will probably comment on
that when he's back online.) Personally I'm happy that the gretl core
has stabilized recently, so I have mixed feelings about such a change.
But it's a very valid point.
cheers,
sven
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