Re: [Gretl-devel] optional arguments (was Re: irf() and fevd())

Am 23.05.2018 um 19:45 schrieb Allin Cottrell: > On Wed, 23 May 2018, Sven Schreiber wrote: > >> (Am I right in assuming that a new alpha argument could be added in >> the future without compromising backwards compatibility? What I mean >> is that a call like fevd(<int>, <bundle>) would still be possible if >> the in the future the signature would be: <int>, <optional-scalar>, >> <bundle>, right?) > > Hmm, not really. You'd need an argument-separating comma, as in > > fevd(<int>,,<bundle>) > > It's true that since the (notional) second and third arguments here > are of different types, we could in principle check the types and > "see" that the argument given second must really be the third one, but > that sort of thing (auto-detection of implicitly omitted optional > arguments) is not supported in geneval.c for any functions at present. > Its also strikes me as kinda tricksy. I found the part of the doc that inspired my hunch, it was in the strsplit help: <help-quote> strings S = strsplit(basket,,",") will split the input into an array of four strings using comma as separator. The “extra” comma in the input above indicates that the i argument is omitted, but it's not strictly necessary unless you wish to extract a single element; if the second argument is a string and only two arguments are given it is understood that sep rather than i is intended. So strings S = strsplit(basket, ",") ... </help-quote> So this only works in this particular function, not in general?