x←(2*¯24)ׯ1e9+?1e6⍴2e9 y←(⍴x)⍴x cmpx 'x⍳x' 'x⍳y' x⍳x → 3.91E¯1 | 0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕ x⍳y → 6.57E¯1 | +68% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕
Self-classification or self-identification. Currently x⍳x is optimized only for 64-bit floats.