vniquify(expressionlist) → expressionlist
The subroutine zniquify takes an array of expressions as argument and returns a copy in which all duplicates have been removed. The items not removed occur in the same order as in the original array.
zniquify runs in quadratic time for lists up to length 10 and n*log n time for larger lists. Keeping the entries in the original order requires a little extra time that makes the quadratic faster on small lists. However, the quadratic dominates on larger lists. Hence the conditional. Compare to uniquify and vniquify.