Commute-Duplicate

Duplicate: Z←f⍨ R      returns R f R.

Commute: Z←L f⍨ R returns R f L.

L and R are arrays.

f is a function.

For example:

      ×⍨⍳5 ⍝ squares
1 4 9 16 25
      ∘.=⍨⍳4 ⍝ Identity matrix
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1

      2*⍨⍳5 ⍝ squares
1 4 9 16 25
      √+/2*⍨6 2⍴3 4, 5 12, 8 15, 7 24, 20 21, 12 35 ⍝ Pythagorean hypotenuses
5 13 17 25 29 37