⍬ — Empty

Literal. Keys: Alt-Shift-0

⍬ is an empty approximate numeric vector: 0⍴0. [] is the same value.

⍬ₓ is the exact empty vector, 0⍴0ₓ, and so is []ₓ.

⍴⍬                 ⍝ [0]ₓ
⍬,1 2              ⍝ 1 2
[]≡⍬               ⍝ $t
1↑⍬ₓ               ⍝ [0]ₓ

Other empty types retain their prototypes.

3↑0⍴0ₓ             ⍝ [0 0 0]ₓ
3↑""               ⍝ "   "

Numbers covers exact and approximate numbers.