OCaml: new_line equivalent before 3.11

Question

I'm trying to compile Libra toolkit on a machine running Ubuntu Hardy with OCaml 3.10, I can't upgrade the OS nor update OCaml, and I don't know anything about OCaml. There is only one line that gives me an unbound value error because it uses the new_line function, which was introduced in OCaml 3.11 (http://caml.inria.fr/pub/docs/manual-ocaml/libref/Lexing.html), could someone tell me how to change it to be compatible with OCaml 3.10? It's the line near the end of this code:

{
open MnParseTypes;;
open MnParser;;
(* Raised when parsing ends *)
exception Eof;;

module L = Lexing
let linenum lexbuf = lexbuf.L.lex_curr_p.L.pos_lnum

let line = ref 1;;

let keywords = Hashtbl.create 10
let _ = 
  List.iter2 (Hashtbl.add keywords)
    ["mn"; "features"; "tree"; "table"; "w"; "eof"]
    [Tmn; Tfeatures; Ttree; Ttable; Tweight; EOF];;
}

let digits = ['0'-'9']+
let identifier = ['a'-'z' 'A'-'Z']+

rule lexer = parse
(* eat blank characters *)
    [' ' '\t'] {lexer lexbuf}
(* | "Feature list:" {lexer lexbuf} *)
  | '{' {Tlbrace}
  | '}' {Trbrace}
  | '(' {Tlparen}
  | ')' {Trparen}
  | ('-')? "inf" {Tfloat( float_of_string(L.lexeme lexbuf))}
  | identifier {
      let x = String.lowercase (Lexing.lexeme lexbuf) in
      try Hashtbl.find keywords x
      with Not_found -> 
        failwith((Lexing.lexeme lexbuf) 
          ^ ": unknown identifier on line " ^ string_of_int (linenum lexbuf))}
  | digits {Tint (int_of_string (L.lexeme lexbuf))}
  | ('-')? digits ('.' digits)? (['e' 'E'] ['+' '-']? digits)? 
      {Tfloat( float_of_string(L.lexeme lexbuf))}
  | '+' 'v' (digits as var) '_' (digits as value) 
      {Tcond(true, int_of_string var, int_of_string value)}
  | '-' 'v' (digits as var) '_' (digits as value) 
      {Tcond(false, int_of_string var, int_of_string value)}
  | 'v' (digits as var) '_' (digits as value) 
      {Tvar( int_of_string var, int_of_string value)}
  | ['\n' '\r']+ {L.new_line lexbuf; TEOL}   (* THIS GIVES THE ERROR *)
  | eof {EOF}
  | _ {failwith((L.lexeme lexbuf) ^ 
       ": mistake on line " ^ string_of_int lexbuf.L.lex_curr_p.L.pos_lnum)}

Answer 1

In the directory of the OCaml sources (from SVN or a relase tarball), the source of the module Foo of the standard library will be in stdlib/foo.{ml,mli} (.mli is the interface file, .ml the implementation file). Looking at stdlib/lexing.ml gives you:

let new_line lexbuf =
  let lcp = lexbuf.lex_curr_p in
  lexbuf.lex_curr_p <- { lcp with
    pos_lnum = lcp.pos_lnum + 1;
    pos_bol = lcp.pos_cnum;
  }

You can implement this in your code as well, using open Lexing to have the field names in scope, or using lexbuf.Lexing.lex_curr_p, and { lcp with Lexing.pos_lnum = lcp.Lexing.pos_lnum ... instead.

Edit: as you probably don't plan to hack the OCaml code yourself, let's give you the full thing:

let new_line lexbuf =
  let lcp = lexbuf.Lexing.lex_curr_p in
  lexbuf.Lexing.lex_curr_p <- { lcp with
    Lexing.pos_lnum = lcp.Lexing.pos_lnum + 1;
    Lexing.pos_bol = lcp.Lexing.pos_cnum;
  }

add this at the top of the file that uses new_line (if it says Lexing.new_line, turn it into new_line), and you should be fine.

Answer 2

You can implement new_line yourself but I think upgrading OCaml would be better. I know that you said you can't upgrade the OS but installing the newer version of Ocaml can be done in your home directory without the need of any superuser privilege. OPAM is a packet manager for OCaml that makes it very easy to install the latest version of OCaml.