r G
0 1 2 3 4 5
1 0 4 5 2 3
2 3 5 4 1 0
3 2 1 0 5 4
4 5 3 2 0 1
5 4 0 1 3 2

   r ∘.{⍺[⍵]}⍨ ↓r G
0 1 2 3 4 5
1 0 4 5 2 3
2 3 5 4 1 0
3 2 1 0 5 4
4 5 3 2 0 1
5 4 0 1 3 2

   (r G) ≡ r ∘.{⍺[⍵]}⍨ ↓r G
1