(* Simple lexer for the Mini-ML language *)

(* Error reporting *)

type message = string

exception Error of message Region.reg

(* Tokeniser *)

(* The call [get_token ~log] evaluates in a lexer (a.k.a
   tokeniser or scanner) whose type is [Lexing.lexbuf -> Token.t].

     The argument [log] is a logger. As its type shows and suggests,
   it is a pair made of an output channel and a printer for
   tokens. The lexer would use any logger to print the recognised
   tokens to the given channel. If no logger is given to [get_token],
   no printing takes place while the lexer runs.

     The call [reset ~file ~line ~offset buffer] modifies in-place the
   lexing buffer [buffer] so the lexing engine records that the file
   associated with [buffer] is named [file], the current line is
   [line] and the offset on that line is [offset]. This function is
   useful when lexing a file that has been previously preprocessed by
   the C preprocessor, in which case the argument [file] is the name
   of the file that was preprocessed, _not_ the preprocessed file (of
   which the user is not normally aware). By default, the [line]
   argument is [1].
*)

type logger = out_channel * (out_channel -> Token.t -> unit)

val get_token  : ?log:logger -> Lexing.lexbuf -> Token.t
val reset      : ?file:string -> ?line:int -> ?offset:int -> Lexing.lexbuf -> unit
val reset_file : file:string ->  Lexing.lexbuf -> unit

(* Debugging *)

type file_path = string

val iter :
  (Lexing.lexbuf -> out_channel -> Token.t -> unit) -> file_path option -> unit

val trace        : file_path option -> unit
val prerr        : kind:string -> message Region.reg -> unit
val format_error : kind:string -> message Region.reg -> string
val output_token : Lexing.lexbuf -> out_channel -> Token.t -> unit