errorFmtFunc = f
}

// uniq swaps away duplicate elements in data, returning the size of the
// unique set. data is expected to be pre-sorted, and the resulting set in
// the range [0:size] will remain in sorted order. Uniq, following a
// sort.Sort call, can be used to prepare arbitrary inputs for use as sets.
func uniq(data sort.Interface) (size int) {
	p, l := 0, data.Len()
	if l <= 1 {
		return l
	}