open Printf

let gen_stream n =
  let rec gs i n =
    if i = n then begin
      printf "making last element of the stream\n"; 
      flush stdout;
      [< 'n >]
    end
    else begin
      if i mod 1000 = 0 then begin
	printf "making next element of the stream: %d\n" i; 
	flush stdout
      end;
      [< 'i; (gs (i+1) n) >] 
    end 
  in
  gs 1 n
	
let rec print_list = function
    []   -> printf "[]\n"
  | h::t -> printf "%d::" h; 
            print_list t

let rec parse_stream s =
  match s with parser
    [< 'i; s' >] -> begin 
      
      if i mod 1000 = 0 then begin
	printf "picked element %d\n" i; 
	flush stdout
      end; 
      
      i::(parse_stream s')
    end
  | [< >] -> (printf "end\n"; flush stdout; [])

let rec parse_stream' s =
  match s with parser
    [< 'i; tail = parse_stream' >] -> begin 
      
      if i mod 1000 = 0 then begin
	printf "picked element %d\n" i; 
	flush stdout
      end; 
      
      i::tail
    end
  | [< >] -> (printf "end\n"; flush stdout; [])

let _ = 
  print_list (parse_stream' (gen_stream 700000))