Dyalog Forums

Thanks Phil, that makes sense.

Would anyone be able to clarify the interaction between the rank and reduction operators? For example, given the following session: +⌿[1]a←2 3 4⍴⍳24 12 15 18 21 48 51 54 57 +/[1]a 12 15 18 21 48 51 54 57 (+⌿⍤2)a 12 15 18 21 48 51 54 57 (+/⍤2)a 6 22 38 54 70 86 it's unclear to me why reduce and reduce ...

Hi John, Glad to hear that folks are interested in this functionality. How tricky do you think it would be to resolve scoping issues as part of a refactor? Presumably some sort of disambiguation prompt ought to be presented so that the programmer can clarify their intended binding(s).... Re: "Wouldn ...

Hi Dick,

Sorry, I should have clarified that index origin was 1:

      ⎕io←1
      foo ← {+⌿⍵}
      bar ← {2*⍨foo⍵}
      foo ⍳3
6
      bar ⍳3
36
      {2*⍨{+⌿⍵}⍵} ⍳3
36
      ⎕io←0
      foo ⍳3
3
      bar ⍳3
9
      {2*⍨{+⌿⍵}⍵} ⍳3
9

Hi Dan, Thanks for your reply. This is a refactoring question—I sometimes have a number of (very) short d-fns defined over the course of a session that are not intended for direct use but rather contribute to a larger expression. Occasionally the larger expression is more meaningful when the e ...

Let's say that I have the following d-fns defined:

      foo ← {+⌿⍵}
      bar ← {2*⍨foo⍵}

      foo ⍳3
  6
      bar ⍳3
  36

Can the call to 'foo' in 'bar' to be inlined—either through the editor or a system function—to yield,

      {2*⍨{+⌿⍵}⍵}

or similar?

Thanks for the clarification, John—interesting to hear that J inspired the implementation of function inverses. Looking over the literature, I see that direct definitions were discussed (in print) at least as early as 1978 (m). My original question was probably overly simplistic; it would have been m ...

Out of curiosity: How influential has J been on the design of D-{fns, ops}, the inclusion of the power operator (especially limits and inverses) and other functional features of "D"?