> > The "tdelete-duplicates" uses a hash-table to store already seen elements: > if the element is in the hash table, just filter it out. If it is not, we > do: (hash-set! already-seen element #t). That should be constant timeish. > I understand how that works for the usual eq? / eqv? / equal? equality relations, but how could that work for *arbitrary* equivalence relations? If you passed a case-insensitive string comparison function to tdelete-duplicates, storing already seen elements in a hash table wouldn't help because two "equal" strings could have different hash codes.
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