Uniq←{
  0=⍴⍴⍵:,⍵
  X←⍵
  c←{⊂⍵}⌸ ⍺⍺ ⍵
  ⍵ ⌷⍨⊂ {⍵[⍋⍵]} ∊ {1≥≢⍵:⍵ ⋄ (⊃⍵)⍪∇ ⍵⌿⍨(X⌷⍨⊂⍵)≢⍤¯1 999⊢(X⌷⍨⊃⍵)}¨ c
}

   cluster ← {((1,2≠/s)/s←⍵[⍋⍵])⍸⍵}

   hd← {⍳⍨ ⍉cluster⍤1⍉ ⍵}         hz← {⍳⍨ ⍉cluster⍤1⍉ |⍵} Tol (2×⎕ct)

   hd Uniq UD 0 rand 666          hz Uniq UD 0j1 rand 666
1                              1
   hd Uniq UT 0                   hz Uniq UT 0j1
1                              1