Write 1-line models of the extended
member ← {(≢⍵)>⍵⍳⍺} unique ← {⍵ ⌿⍨ (⍳≢⍵)=⍵⍳⍵} without ← {⍺ ⌿⍨ ~(⍺⍳⍺)∊,⍺⍳⍵} intersect ← {⍺ ⌿⍨ (⍺⍳⍺)∊,⍺⍳⍵} union ← {⍺⍪(↑,⊂⍤(¯1+⍴⍴⍺)⊢⍵) without ⍺}