Double Acute Accent (˝)

𝔽˝ 𝕩: Insert

Fold over 𝕩 with 𝔽 from right to left i.e. Insert 𝔽 between the major cells of 𝕩.

       a ← 3‿3 ⥊ ↕9

       +˝ a
⟨ 9 12 15 ⟩

       0‿1‿2 + 3‿4‿5 + 6‿7‿8
⟨ 9 12 15 ⟩

𝕨 𝔽˝ 𝕩: Insert With initial

Monadic insert, but use 𝕨 as initial right argument.

If

       b ← 3‿3 ⥊ ↕9

       1‿1‿1 +˝ b
⟨ 10 13 16 ⟩

       1 +˝ b
⟨ 10 13 16 ⟩

       0‿1‿2 + 3‿4‿5 + 6‿7‿8 + 1‿1‿1
⟨ 10 13 16 ⟩