`∪` — Unique / Union

Function. Keys: Alt-v. Ranks: ∞ monadic, ∞ ∞ dyadic

∪Y keeps the first of each matching major cell. Uses tolerant matching.

∪3 1 3 2 1         ⍝ 3 1 2

∩ and ⍷ give the duplicates and positions of the same distinct cells. ≢¨⍷Y gives how many times each one occurs.

X∪Y appends the major cells of Y absent from X. Order and repetitions are retained.

1 2∪2 3            ⍝ 1 2 3
1 1∪2 2            ⍝ 1 1 2 2
[1 2⋄3 4]∪[3 4⋄5 6] ⍝ [1 2⋄3 4⋄5 6]

Errors