(* preventively allocate the space for the following elements *)
let nlen = ((i - offset + 1) lsl 1) + 1 in
let narray = Array.create nlen a.dummy in
(* preventively allocate the space for the following elements *)
let nlen = ((i - offset + 1) lsl 1) + 1 in
let narray = Array.create nlen a.dummy in