Re: Index-of function with structured left-argument

[Hans-Peter Sorge]

    Hi,
    
    Your ⎕IO is 0
     
    ⎕IO←1
      
          Display (2 2 ⍴ 104 105 106 107) ⍳ (3 4 ⍴ 100+⍳100)
    ┏→━━━━━━━━━━━━━━━━━━━━━━┓
    ↓┏⊖┓   ┏⊖┓   ┏⊖┓   ┏→━━┓┃
    ┃┃0┃   ┃0┃   ┃0┃   ┃1 1┃┃
    ┃┗━┛   ┗━┛   ┗━┛   ┗━━━┛┃
    ┃┏→━━┓ ┏→━━┓ ┏→━━┓ ┏⊖┓  ┃
    ┃┃1 2┃ ┃2 1┃ ┃2 2┃ ┃0┃  ┃
    ┃┗━━━┛ ┗━━━┛ ┗━━━┛ ┗━┛  ┃
    ┃┏⊖┓   ┏⊖┓   ┏⊖┓   ┏⊖┓  ┃
    ┃┃0┃   ┃0┃   ┃0┃   ┃0┃  ┃
    ┃┗━┛   ┗━┛   ┗━┛   ┗━┛  ┃
    ┗∊━━━━━━━━━━━━━━━━━━━━━━┛
      ⍝ this is the shape of the right argument and their indexes within
      the left argument. 
      
      
            (2 2 ⍴ 104 105 106 107)  (3 4 ⍴ 100+⍳12)
       104 105   101 102 103 104
       106 107   105 106 107 108
                 109 110 111 112
      
    furthermore: 
         104 105 106 107 ⍳  3 4 ⍴ 100+⍳12
    5 5 5 1
    2 3 4 5
    5 5 5 5
      
      so may be 
    (2 2 ⍴ 104 105 106 107) ⍳ (3 4 ⍴ 100+⍳100)
        
        should be
        
        ┏→━━━━━━━━━━━━━━━━━━━━━━┓
        ↓┏→━━┓ ┏→━━┓ ┏→━━┓ ┏→━━┓┃
        ┃┃3 3┃ ┃3 3┃ ┃3 3┃ ┃1 1┃┃
        ┃┗━━━┛ ┗━━━┛ ┗━━━┛ ┗━━━┛┃
        ┃┏→━━┓ ┏→━━┓ ┏→━━┓ ┏→━━┓┃
        ┃┃1 2┃ ┃2 1┃ ┃2 2┃ ┃3 3┃┃
        ┃┗━━━┛ ┗━━━┛ ┗━━━┛ ┗━━━┛┃
        ┃┏→━━┓ ┏→━━┓ ┏→━━┓ ┏→━━┓┃
        ┃┃3 3┃ ┃3 3┃ ┃3 3┃ ┃3 3┃┃
        ┃┗━━━┛ ┗━━━┛ ┗━━━┛ ┗━━━┛┃
        ┗∊━━━━━━━━━━━━━━━━━━━━━━┛
        
        Regards 
        Hans-Peter

Am 14.04.20 um 11:30 schrieb Jay Foad:

Just from staring at the result, it looks like the result of ⍺⍳⍵ has the same shape as ⍵, and for each item of ⍵ it tells you either the coordinates where it was found in ⍺, or ⍬ if it was not found. (Dunno what it does if ⍺ is a scalar, where ⍬ would be a valid coordinate.)

N.B. in Dyalog APL dyadic iota has been extended to high rank arrays in a completely different way: https://help.dyalog.com/17.1/#Language/Primitive%20Functions/Index%20Of.htm

Jay.

On Tue, 14 Apr 2020 at 09:15, Elias Mårtenson <address@hidden> wrote:

The ISO spec doesn't address what the index-of function should do when the left argument is not a scalar or a one-dimensional array.

GNU APL extends this, but I don't really understand in what way. How am I to interpret the output from this?

      (2 2 ⍴ 104 105 106 107) ⍳ (3 4 ⍴ 100+⍳100)
┏→━━━━━━━━━━━━━━━━━━━━━━┓
↓┏⊖┓   ┏⊖┓   ┏⊖┓   ┏⊖┓  ┃
┃┃0┃   ┃0┃   ┃0┃   ┃0┃  ┃
┃┗━┛   ┗━┛   ┗━┛   ┗━┛  ┃
┃┏→━━┓ ┏→━━┓ ┏→━━┓ ┏→━━┓┃
┃┃0 0┃ ┃0 1┃ ┃1 0┃ ┃1 1┃┃
┃┗━━━┛ ┗━━━┛ ┗━━━┛ ┗━━━┛┃
┃┏⊖┓   ┏⊖┓   ┏⊖┓   ┏⊖┓  ┃
┃┃0┃   ┃0┃   ┃0┃   ┃0┃  ┃
┃┗━┛   ┗━┛   ┗━┛   ┗━┛  ┃
┗∊━━━━━━━━━━━━━━━━━━━━━━┛

Regards,

Elias