v←?⍴z

   z[⊂v] = y[⊂v[x]]
1
   z[⊂v] = y[⊂(⊂x)⌷v]
1
   z ≡ y[(⊂⊂x) ⌷¨ ⍳⍴z]
1


   tr ← {⍵[(⊂⊂⍺) ⌷¨ ,¨ ⍳ ⍺[⍋⍺] {⌊/⍵}⌸ (⍴⍵)[⍋⍺]]}


   (x⍉y) ≡ x tr TC y
1
   (x⍉y) ≡ x tr y
1