≠ — Unique mask / Not equal

Function. Keys: Alt-Shift-=. Ranks: ∞ monadic, 0 0 dyadic

≠Y marks the first occurrence of each distinct major cell. Tolerance decides which cells are distinct.

≠3 1 3 2 1         ⍝ $t $t $f $t $f

X≠Y tests inequality, pervasively.

1 2 3≠2            ⍝ $t $f $t

Inverse

On Booleans, ≠ is its own inverse with either argument fixed.

1 0≠⁻¹1 1   ⍝ $f $t