Passing a User-Defined Function as a Argument

[REMINGTON30]

Consider a dyadic user-defined function x Dy y which produces a result. Is there a way to pass the function Dy to another function as an argument? For example, if a monadic function Gg F1 requires function Dy to operate, is there a way to put Dy in the argument F1?

[Phil Last]

To answer your question directly, what you could do is create a namespace

      ns←⎕NS'Dy'

and pass the namespace as an argument or a part of an argument to Gg. Within Gg you could then call

      arg.Dy

A problem is that if Dy had dependencies then inside the namespace above represented by arg there would be none of them. No doubt there are even more perverse ways to do it but the straightforward APL way is to make Gg an operator rather than a function. Operators take functions as arguments (operands) which can be called from within 'though they actually operate in the environment where they reside.

      .
 Gg←{
   ...
   z←⍺⍺ ⍵ ⍝ runs Dy
   ...
 }
      Dy Gg F1

[REMINGTON30]

Thanks Phil. I will read the Dyalog documentation on user-defined operators and try that method.