Thank you Jürgen. --David
On Fri, Dec 27, 2019 at 2:11 PM Dr. Jürgen Sauermann < mail@jürgen-sauermann.de> wrote: > Hi again, > > I have done a rework of the EACH operator so that your example > (and similar ones) should work now. *SVN 1213*. > > However, please keep the following in mind: Since > selective specification is not a standard feature (and > quite complicated compared to other functions, there is > still a high probability that some cases were not caught > properly. Your example, for instance, survived for almost > a decade before you discovered it. > > For that reason I would recommend that everybody who is > writing business critical applications in GNU APL should > use not-so-standard features only if the benefit that they > provide is significant and make sure that the code is being > tested thoroughly. > > Best Regards, > Jürgen > > > On 12/27/19 12:22 PM, Dr. Jürgen Sauermann wrote: > > Hi David, > > your example touches a somewhat dubious area. Its name is > Selective assignment (basically using functions left of ←where > the functions compute what is being assigned), > > Selective assignment is defined in APL2 but not in the APL2 ISO > standard (APL2 is named extended APL there). > > And even in APL2 there are restrictions (as the IBM APL2 language > reference says: > *"The information in this section is based on the APL2 language > definition.* > * Deviations exist on some platforms and are documented in the separate > user's** guides."* > > GNU APL supports most, but not all, selective specifications that APL2 > does. > The only not supported case that I am aware of is monadic and dyadic > EACH (¨). The reason is that in GNU APL EACH is a macro (a defined function > that is only used internally). The syntax error probably comes because in > APL2 > selective specification is only allowed for certain primitive functions > left of ← but > not for defined functions. > > I will look into this to see if it is feasible to fix it. The primary > reason why macros > were introduced in GNU APL was primitive operators with defined functions. > Here we only have a primitive operator with primitive functions, which > makes > things a lot simpler. > > Best regards, > Jürgen > > > On 12/27/19 5:37 AM, David Tran wrote: > > Hi, > > Currently study APL2, and found an example that won't work on Gnu APL: > > v ← 12(13(14 15))(16 17) > (↑¨v) ← 2 3 6 > > On the book, above statement will change v into 2 (3 (14 15)) (6 17); > however Gnu APL returns Syntax Error. > > Is such "first each assignment" not APL2 standard specification, or it is > just Gnu APL is not support yet? > > > Thanks, > Dave > > > >
