Exercise: Nub (Unique) Index   <<   >>


  Morten, vecdb application, 2016-09-28:

   t  ← '/zero/one/two/three/four/five/six/seven/eight/nine/ten'
   t ,← '/eleven/one dozen/thirteen/fourteen/fifteen'
   t  ← {1↓¨(⍵=⊃⍵)⊂⍵} t
   t
┌────┬───┬───┬─────┬────┬────┬───┬─────┬   ┬───────┐
│zero│one│two│three│four│five│six│seven│...│fifteen│
└────┴───┴───┴─────┴────┴────┴───┴─────┴   ┴───────┘

   x ← t[ ? 5e6 ⍴ ≢t ]

Derive a faster computation for ∪x .   Hint: ↑x has been sped up in v15.0.