anchor.diff:                  else
                       fst children.[0]
   
  -            let rootPage = writeOneLayerOfParentPages pageAfterLeaves boundaryAfterLeaves (List.rev (List.ofSeq leaves))
  +            let rootPage = writeOneLayerOfParentPages pageAfterLeaves boundaryAfterLeaves leaves
   
               pageManager.End(token, rootPage)
               rootPage
  
positive.code:         // maybe more than one level of them.
          // keep writing until we have written a level which has only one node,
          // which is the root node.
          if leaves.Count > 0 then
              let firstLeaf = fst leaves.[0]
              let lastLeaf = fst leaves.[leaves.Count-1]
  
              let writeParentNodes children startingPageNumber startingBoundaryPageNumber =
                  // 2 for the page type and flags
  
negative.code:             let LEAF_PAGE_OVERHEAD = 2 + 4 + 2 + 4
              let OFFSET_COUNT_PAIRS = 6
  
              let flushLeaf st isRootPage = 
                  pb.PutInt16At (OFFSET_COUNT_PAIRS, st.keys.Length)
                  let thisPageNumber = st.nextPage
                  let (nextN,nextB) = 
                      if (not isRootPage) && (thisPageNumber = st.boundaryPage) then
                          pb.SetPageFlag FLAG_BOUNDARY_NODE
                          let newRange = pageManager.GetRange(token)
                          // assert pb.Position <= (pageSize - 4)
                          pb.SetLastInt32(fst newRange)
                          newRange
                      else
                          (thisPageNumber + 1, st.boundaryPage)
                  pb.Flush(fs)
                  pb.Reset()
                  if nextN <> (thisPageNumber+1) then utils.SeekPage(fs, pageSize, nextN)
                  {keys=[]; nextPage=nextN; boundaryPage=nextB; leaves=(thisPageNumber,List.head st.keys)::st.leaves}
  
              let folder st (pair:(byte[]*Stream)) = 
                  let (k,v) = pair
                  // assert k <> null
                  // but v might be null (a tombstone)
  
  