Re: Issues with drop of a scalar argument

[Dr . Jürgen Sauermann]

Hi Kacper, thanks, see below. On 4/25/20 12:03 AM, Kacper Gutowski wrote: 1° With left argument longer than one, the scalar is properly extended to a higher rank one-element array, but then it's not dropped correctly unless all axes are non-zero.       ⊢X← 1 0↓2 2       ⍴X 1 1 The X here should be an empty array (0 1⍴0) but is (1 1⍴2). Fixed in SVN 1271 2° When left argument has one non-zero element and right is a non-zero scalar, the returned result is a weird value that looks like the correct one (0⍴0), but is distinct, and isn't transferable.       8⎕CR Y← 1↓1 ┌⊖┐ │0│ └─┘       ⍬≡Y ⍝ should be true 0       (11⎕CR⍬)≡(11⎕CR Y) 1       Y ≡ 12⎕CR 11⎕CR Y 0 Fixed in SVN 1271 3° This might not be an error, but I find it surprising:       3 ≡ ''↓3  ⍝ this is correct 1 yes. But ISO has an example ''↓5 which looks the same.       ''↓⍳3  ⍝ this is an extension (length error by ISO) 2 3 Fixed in SVN 1271. Now gives length error.       ''↓⍳3 3 LENGTH ERROR       ''↓⍳3 3       ^  ^ Should be correct shape lengths are: left 0, right 2. By my reading of ISO, when left argument is empty, the right must be a scalar (or it will be a length error) which is returned unchanged.  In Dyalog it's extended such that any value is returned unchanged, in GNU APL ⍬↓X ←→ 1↓X for non-scalar X.  Is this intended and correct?  (Is that what APL2 does?) -k The 2 ⎕TF looks slightly better now (your first example works, the second not). I'll keep working on iy. Bst regards, Jürgen