Why is the second expression, the longer expression, so much faster than the first?
n← 10 2 ⍴ 1 2 3 1 2 m← 10 3 ⍴ 10×1 2 3 1 cmpx ' n {+⌿⍵}⌸m' '(n⍳n){+⌿⍵}⌸m' n {+⌿⍵}⌸m → 1.48E¯5 | 0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕ (n⍳n){+⌿⍵}⌸m → 1.20E¯6 | -92% ⎕⎕
query from user, 2018-10-18