Re: /⍨

[Dr . Jürgen Sauermann]

    Hi Hudson,
      
      I checked with IBM APL2.
      
      Unfortunately my IBM APL2 has no ⍨ (aka. duplicate) operator.
      But we can emulate it easily:
      
            DUP ←{ ⍵ ⍶ ⍵ }
              + DUP 1 2 3
        2 4 6
              × DUP 1 2 3
        1 4 9
      
      In GNU APL, DUP gives the same result as ⍨:
      
            /⍨1 2 3
          SYNTAX ERROR
                /⍨1 2 3
                ^^
          
                /DUP 1 2 3
          SYNTAX ERROR
                /DUP 1 2 3
                ^^
        
      However, in IBM APL2 I get the same (see attached screenshot),
      
      The problem seems to be caused by the ambiguity of / and friends
      (i.e. ⌿, \, and
        ⍀).
      You can work around this with a wrapper around /:
      
            REPL←{ ⍺ / ⍵ }   ⍝ disambiguates /
          to mean replicate and not reduce
                3 REPL 1 2 3
          1 1 1 2 2 2 3 3 3
          
                REPL ⍨ 1 2 3
          1 2 2 3 3 3
      
                1 2 3 REPL 1 2 3   ⍝ same as REPL ⍨ 1 2 3
              1 2 2 3 3 3
      
      
      Best Regards,
      Jürgen

On 5/31/22 2:18 AM, hudson@hudsonlacerda.com wrote:

> Hi.
>
> I get "SYNTAX ERROR" messages for /⍨ or ⌿⍨ :
>
> /⍨⍳3
> ⌿⍨⍳3
>
> Regards,
> Hudson
>
>

Duplicate-APL2.png
Description: PNG image