Re: [Bug-apl] an other inner product ,., bug

[Juergen Sauermann]

Hi Jay, yes. Even worse: there is another subtle difference in the inner products of IBM APL2 and the ISO standard. IBM APL2 states (language reference, page 165) and also does this: A f.g B  ←→  f/¨ (⊂[⍴⍴A]A) ∘.g ⊂[1]B The ISO standard follows suit, except that it has a special case for A and B being vectors: "If A and B are both vectors, return f/A g B."   (ISO standard, page 121 with A=A1 and B=B1). GNU APL follows the ISO standard, so in David's example A g B is 1 2 3 , 4 5 6 (or: 1 2 3 4 5 6) and ,/1 2 3 4 5 6 is ⊂(1 2 3 4 5 6). The enclose is needed because the reduction of a vector has to be a scalar (according to the Implementation parameter  "Enclose-Reduction-Style" which GNU APL and IBM APL2 have chosen). Best Regards, /// Jürgen On 05/18/2018 03:31 PM, Jay Foad wrote: This is a subtle difference in the definition of inner product. On vectors: A f.g B  ←→  ⊂f/A g B  ⍝ APL2 A f.g B  ←→  f/A g¨ B  ⍝ NARS2000, Dyalog Jay. On 17 May 2018 at 17:52, David Tran <email55...@gmail.com> wrote: Hi, Below shows the bug: 1 2 3 ,., 4 5 6 result: 1 2 3 4 5 6 expected: 1 4 2 5 3 6 Thanks, David

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