I think such a change would make sense. A niladic function is in some sense a shortcut to writing a specific value, so it should probably be treated as such.
It a little odd that: 1 2 X 4 is different from: 1 2 (X) 4 Regards, Elias On Tue, 24 Dec 2019, 14:48 Dr. Jürgen Sauermann, <mail@jürgen-sauermann.de> wrote: > Hi David, > > not sure either if this is a bug. The APL standard has quite a > specification gap > when it comes to binding strength. In GNU APL, the binding between values > (aka strand notation) is stronger than the binding between values and > functions. > > For example: > > * V←⍳0* > > *∇Z←F* > * Z←⍳0* > *∇* > > Both V and F result in the same value *⍬*: > > * V≡F* > *1* > > However, they are parsed differently: > > * 2 V 3⊃a* > > > *3 ** 2 F 3⊃a* > * 2 99 * > > In the first case: *2 V 3⊃a* the value *V* binds strongly to 2 and 3 so > that value *(2 V 3)* > becomes the left argument of *⊃*. In the second case: *2 F 3* the value > 3 binds > stronger to *⊃* than to *F* so that first is evaluated *3⊃a* and then > the result of *⊃* is > tied to the *F* and *2*. > > In GNU APL *⍬* is a niladic function, so it behaves like *F* above. > > This behaviour could be changed, but I hesitate to do that since it might > break > existing code. The impact of such a change would not only affect *⍬* but > all niladic > functions. > > Best Regards, > Jürgen Sauermann > > > On 12/24/19 2:49 AM, David Tran wrote: > > Ooops, missing something on my examples, correction: ( missing ⊂ on ⍳3 ) > > a ← 'abc'(⊂⍳3)99 > > the 3 examples are the same: > 2(⍳0)3⊃a > 2⍬3⊃a > (2⍬3)⊃a > > On Mon, Dec 23, 2019 at 7:20 PM David Tran <email55...@gmail.com> wrote: > >> Hi, >> >> Not sure this is a bug or not, for me, (⍳0) ≡ ⍬, so it seems that both >> can be replaced each other; consider below example: >> >> a←'abc'(⍳3)99 >> >> 2(⍳0)3⊃a ⍝ ≡ 3 >> 2⍬3⊃a ⍝ ≡ 2 ⍬ 99 >> (2⍬3)⊃a ⍝ ≡ 3 >> >> Doesn't the second example should return 3 as first example, without the >> need parentheses as third example? >> >> (btw. my version is build from SVN around Oct ) >> >> >> Thanks, >> Dave >> >> >> >> >
