+// ugh, c&p
+template<typename T> void
+vector_sort (vector<T> &v, int (*compare) (T const &, T const &),
+ vsize lower=VPOS, vsize upper=VPOS)
+{
+ if (lower == VPOS)
+ {
+ lower = 0;
+ upper = v.size () - 1;
+ }
+ if (upper == VPOS || lower >= upper)
+ return;
+ swap (v[lower], v[(lower + upper) / 2]);
+ vsize last = lower;
+ for (vsize i = lower +1; i <= upper; i++)
+ if (compare (v[i], v[lower]) < 0)
+ swap (v[++last], v[i]);
+ swap (v[lower], v[last]);
+ vector_sort (v, compare, lower, last - 1);
+ vector_sort (v, compare, last + 1, upper);