Since Ocaml 3.08
The position information on scanning the input text is recorded in the lexbuf which has a field lex_curr_p of the type position:
type position = {
pos_fname : string; (* file name *)
pos_lnum : int; (* line number *)
pos_bol : int; (* the offset of the beginning of the line *)
pos_cnum : int; (* the offset of the position *)
} The value of pos_bol field is the number of characters between the beginning of the file and the beginning of the line while the value of pos_cnum field is the number of characters between the beginning of the file and the position.
The lexing engine manages only the pos_cnum field of lexbuf.lex_curr_p with the number of characters read from the start of lexbuf. So you are reponsible for the other fields to be accurate. Typically, whenever the lexer meets a newline character, the action contains a call to the following function:
let incr_linenum lexbuf =
let pos = lexbuf.Lexing.lex_curr_p in
lexbuf.Lexing.lex_curr_p <- { pos with
Lexing.pos_lnum = pos.Lexing.pos_lnum + 1;
Lexing.pos_bol = pos.Lexing.pos_cnum;
}
;;