Re: [Gretl-devel] scalar function args and NAs
On Sun, 5 Jul 2015, Allin Cottrell wrote:
A question has come up as I've thought about user-function
arguments (see
also
http://lists.wfu.edu/pipermail/gretl-devel/2015-July/005850.html )
Given a scalar parameter, what do we want to do if the caller supplies NA as
an argument? What difference, if any, should it make if the parameter is
marked as "bool" or "int" rather than plain "scalar"?
The situation prior to my changes of the last couple of days was that
NA was always accepted. But along with fixing the bounds checking for scalar
arguments, I banned NA for bool and int parameters. I've now had second
thoughts (maybe this would break some existing scripts?) and have reverted to
the status quo ante.
But maybe this is something we want to think about. Are there real use-cases
where a function writer would want to accept NA for a bool or int argument?
Or would it be more convenient for the writer not to have to bother with
checking for NAs, in the knowledge that they would be ruled out by gretl?
My very personal position is not to check automatically. It shifts the
burden on "do the right thing" on the function writer, who should bear
responsibility for what she does.
Besides, NA could very well be an idiomatic way of saying "make some
automatic choice", which can be very useful at times (think for example
lags in a unit-root test).
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Riccardo (Jack) Lucchetti
Dipartimento di Scienze Economiche e Sociali (DiSES)
Università Politecnica delle Marche
(formerly known as Università di Ancona)
r.lucchetti(a)univpm.it
http://www2.econ.univpm.it/servizi/hpp/lucchetti
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