[Gretl-devel] scalar function args and NAs

Allin Cottrell cottrell at wfu.edu
Sun Jul 5 13:24:02 EDT 2015


On Sun, 5 Jul 2015, Sven Schreiber wrote:

> Am 05.07.2015 um 17:08 schrieb Allin Cottrell:
>
>> 
>> 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?
>> 
>
> Well, NaN rather than NA, but since they're not differentiated in gretl:
> In principle I could imagine that a function has the log-value of something 
> as its input. Then the caller could write:
>
> thefunc(log(thisvalue))
>
> which could end up as thefunc(NA) for thisvalue <= 0. The question then is 
> really who should bear the burden of sanity checking, the function or the 
> caller.

Thanks, Sven. The log example would seem to pertain to parameters 
marked as plain "scalar" rather than int or bool. My point was that 
for int and bool parameters there's potentially a third option: 
gretl itself could bear the burden of sanity checking -- unless, 
that is, there's a real case for user-functions that are OK with 
getting NAs for ints or bools. (Presumably such functions would 
check for NA and treat it as meaning "not applicable".)

Allin


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