The Constant (⍨) operator

Dyalog 17.1 defines ⍨ with a function operand ("Commute").

Dyalog 18.0 will allow an array operand: A⍨ is the function which returns A.

ranks ← ∧/(⍳13)∊⍨⊣/
suits ← ∧/(⍳4)∊⍨⊢/

ranks ← ∧/⊣/∊(⍳13)⍨
suits ← ∧/⊢/∊(⍳4)⍨

The derived function A⍨ behaves identically to A{⍺⍺}, or the train (A⊣⊢). But it's different from {A}, which looks up the name A when run.

attrs ← ∧/¨ ↓∘⍉ ∊¨ (⍳¨13 4)⍨

attrs ← (↓⍉) (∧/∊)∘⍳¨ 13 4⍨