Cubicle 1.1.2 documentation and source : Iheap.filter

let filter s filt cmp = 
  let j = ref 0 in
  let lim = Vec.size s.heap in
  for i = 0 to lim - 1 do
    if filt (Vec.get s.heap i) then begin
      Vec.set s.heap !j (Vec.get s.heap i);
      Vec.set s.indices (Vec.get s.heap i) !j;
      incr j;
    end
    else Vec.set s.indices (Vec.get s.heap i) (-1);
  done;
  Vec.shrink s.heap (lim - !j);
  for i = (lim / 2) - 1 downto 0 do
    percolate_down cmp s i
  done