let identifier x =
let range a c b = a <= c && c <= b in
let buffer = Buffer.create 80 in
for i=0 to String.length x - 1 do
let c = x.[i] in
if range 'a' c 'z'
|| range 'A' c 'Z'
|| (i > 0 && range '0' c '9')
|| c = '_'
then
Buffer.add_char buffer c ;
done ;
Buffer.contents buffer