let string_to_sort s =
try begin
match (String.get s 0) with (* Depending on the first letter *)
| 'a' -> Alpha
| 'g' -> let regexp = Str.regexp "grade\\([0-9\\.]*\\)" in
if (Str.string_match regexp s 0) then
let gadd = pa_of_string (Str.matched_group 1 s) in Grade gadd
else No_order
| 't' -> let regexp = Str.regexp "team\\([0-9\\.]*\\)" in
if (Str.string_match regexp s 0) then
let tadd = pa_of_string (Str.matched_group 1 s) in Team tadd
else No_order
| _ -> No_order
end with _ -> No_order