STV.aplf

 res←STV ballot;votes;table;voters;max;eliminated
  ⍝ Perform the Single Transferrable Vote logic
  ⍝ Currently supports only one winner

  ⍝ Tally the primary votes per candidate
  votes←⊃+/ballot[;1]×1=ballot[;2]

  ⍝ Generate tally table to show in results
  table←↑[1](⍳⍴votes)(votes)
  res←⊂(table[;2]≠0)⌿table

  ⍝ Tally the number of active voters, i.e. who have at least one vote >0
  voters←+/ballot[;1]×⊃∨/¨0<ballot[;2]

  max←⌈/votes

  ⍝ Check if we have a winner
  :If voters≤2×max
    ⍝ Check if there is a unique winner
    :If 1=+/votes=max
      res←res,votes⍳max
    :EndIf
    →0
  :EndIf

  ⍝ Eliminate the elements with the least (or zero) votes
  eliminated←((votes=0)∨votes=⌊/(0≠votes)/votes)/⍳⍴votes

  ⍝ Repeatedly delete eliminated first preferences
  ballot[;2]←{0⌈⍵-(⍵⍳¨1)∊,eliminated}⍣≡ballot[;2]

  ⍝ Recurse
  res←res,STV ballot