⍢ — Operator self-reference

Inside a dop, ⍢ denotes the operator itself. Apply operands again to derive the recursive function; ∇ instead retains the current operands.

op←{⍵=0:0 ⋄ 1+(⍶ ⍢)⍵-1} ⋄ (+op)3 ⍝ 3