Re: [Bug-apl] multiple inner product

[Juergen Sauermann]

Hi, it looks to me like that the discussion on comp.lang.apl exactly hits the issue. I have simplified Xiao-Yong's example a little and compared GNU APL with IBM APL2. In IBM APL2 we have:       Q←(1 2) (3 4)       ⍴Q 2       ≡Q 2       DISPLAY Q ┏→━━━━━━━━━━┓ ┃┏→━━┓ ┏→━━┓┃ ┃┃1 2┃ ┃3 4┃┃ ┃┗∼━━┛ ┗∼━━┛┃ ┗∊━━━━━━━━━━┛       +/Q  4 6       ⍴+/Q       ≡+/Q 2       DISPLAY +/Q ┏━━━━━┓ ┃┏→━━┓┃ ┃┃4 6┃┃ ┃┗∼━━┛┃ ┗∊━━━━┛       Q +.+ Q   8 12       ⍴Q +.+ Q       ≡Q +.+ Q 3       DISPLAY Q +.+ Q ┏━━━━━━━━┓ ┃┏━━━━━━┓┃ ┃┃┏→━━━┓┃┃ ┃┃┃8 12┃┃┃ ┃┃┗∼━━━┛┃┃ ┃┗∊━━━━━┛┃ ┗∊━━━━━━━┛ In GNU APL we have:       Q←(1 2) (3 4)       ⍴Q 2       ≡Q 2       4 ⎕CR Q ┏→━━━━━━━━━━┓ ┃┏→━━┓ ┏→━━┓┃ ┃┃1 2┃ ┃3 4┃┃ ┃┗━━━┛ ┗━━━┛┃ ┗∊━━━━━━━━━━┛             ⍴+/Q       ≡+/Q 2       4 ⎕CR +/Q ┏━━━━━┓ ┃┏→━━┓┃ ┃┃4 6┃┃ ┃┗━━━┛┃ ┗∊━━━━┛             ⍴Q+.+Q       ≡Q+.+Q 2       4 ⎕CR Q+.+Q ┏━━━━━━┓ ┃┏→━━━┓┃ ┃┃8 12┃┃ ┃┗━━━━┛┃ ┗∊━━━━━┛ That means in short that GNU APL and IBM APL2 have identical results for the +/Q but for Q+.+Q the IBM APL2 result is nested one level deeper. This is a discrepancy between IBM APL2 and the ISO standard. Even though I normally go for IBM compatibility in such cases, I would prefer ISO in this case. It could even be that IBM has fixed this in the meantime (my APL2  is fairly old). /// Jürgen On 07/07/2016 12:57 PM, Jay Foad wrote: There was some relevant discussion in comp.lang.apl here: https://groups.google.com/forum/#!topic/comp.lang.apl/23LrwRZKmPs On 6 July 2016 at 19:31, Xiao-Yong Jin <jinxiaoy...@gmail.com> wrote: The following from GNU APL,       (⊂[1]⍳2 3)+.+.+⊂[1]10×⍳2 3  209 198       (⊂[1]⍳2 3)(+.+).+⊂[1]10×⍳2 3  209 198       (⊂[1]⍳2 3)+.(+.+)⊂[1]10×⍳2 3   33 66  66 66 do not agree with Dyalog APL,       ⎕ML 3       (⊂[1]⍳2 3)+.+.+⊂[1]10×⍳2 3   165 242       (⊂[1]⍳2 3)(+.+).+⊂[1]10×⍳2 3   165 242       (⊂[1]⍳2 3)+.(+.+)⊂[1]10×⍳2 3   99 132 I’m not sure which one is at fault here.  Any idea?