Re: Five-dimensional transpose results in incorrect shape

[Dr . Jürgen Sauermann]

Hi, the IBM APL2 language reference says (page 251): if Z←L⍉R then: (⍴Z) ←→ (⍴R)[⍋L] In our case we have (GNU APL):       ⎕IO←0       R←3 4 5 6 7 ⍴ ⍳100       L←2 4 1 0 3       Z←L⍉R       ⍴Z 6 5 3 7 4       (⍴R)[⍋L] 6 5 3 7 4 Dyalog seems to give the same ⍴Z (haven't compared the ravel of Z though :-)). Best Regards, Jürgen On 3/10/20 7:36 PM, Kacper Gutowski wrote: On Wed, Mar 11, 2020 at 12:57:09AM +0800, Elias Mårtenson wrote: Now, for the problematic version: *      ⍴ 2 4 1 0 3 ⍉ 3 4 5 6 7 ⍴ ⍳100* ┏→━━━━━━━━┓ ┃6 5 3 7 4┃ ┗━━━━━━━━━┛ As you can see, the numbers are all over the place. For some reason, it seems to have interpreted the left arguments to transpose as if they were: 3 2 0 4 1 They aren't just “all over the place,” if you consider it as a permutation on shape list, it's an inverse of a permutation you expected (previous three cases happened to be self-inverses!). You expected that Z≡⍴A⍉B⍴⍳100 iff Z≡B[A] but it's actually Z[A]≡B.       (6 5 3 7 4)[2 4 1 0 3] 3 4 5 6 7 If I read the ISO right, it seems to be correct: values in left argument correspond to axes of result and positions to axes of right argument. -k