# Structure Location

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    (* Location -- error reporting for mosmllex and mosmlyac               *)
    (* Based on src/compiler/location from the Caml Light 0.6 distribution *)

    datatype Location =  (* Source file positions                            *)
        Loc of int       (* Position of the first character                  *)
             * int       (* Position of the character following the last one *)

    val errLocation : string * BasicIO.instream * Lexing.lexbuf -> Location
                      -> unit
    val errMsg      : string * BasicIO.instream * Lexing.lexbuf -> Location
                      -> string -> 'a
    val errPrompt   : string -> unit;
    val nilLocation : Location
    val getCurrentLocation : unit -> Location
    val mkLoc : 'a -> Location * 'a
    val xLR   : Location * 'a -> Location
    val xL    : Location * 'a -> int
    val xR    : Location * 'a -> int
    val xxLR  : Location * 'a -> Location * 'b -> Location
    val xxRL  : Location * 'a -> Location * 'b -> Location

    (*
       These functions support error reporting in lexers and parsers
       generated with mosmllex and mosmlyac.  The directory
       mosml/examples/lexyacc/ contains an example of their use.

       [errLocation (file, stream, lexbuf) loc] prints the part of the lexer
       input which is indicated by location loc.

       If file <> "" then it is assumed to be the name of the file from
       which the lexer reads, the stream is assumed to be an open input
       stream associated with this file, and lexbuf is the lexer buffer
       used to read from the stream.  Under MS DOS (and presumably
       Windows, OS/2, and MacOS), the stream must have been opened in
       binary mode (with Nonstdio.open_in_bin), or else the positioning in
       the file will be wrong (due to the translation of CRLF into
       newline in text files).

       If file = "" then the lexer is assumed to read from some source
       other than a stream, and the lexbuf (rather than the instream) is
       used to obtain the location indicated, if possible.  In this case
       the stream is immaterial; it will not be used.

       [errMsg (file, stream, lexbuf) loc msg] calls errLocation to print
       the indicated part of the lexer input, then prints the error
       message msg and raises exception Fail.

       [errPrompt msg] prints "! ", the string msg, and a newline on
       standard output.

       [nilLocation] is the undefined location.

       [getCurrentLocation ()] can be called within the semantic action
       part of a grammar rule (only) and returns the location of the
       string matching the left-hand side of the rule.

       [mkLoc a] can be called within the semantic action part of a
       grammar rule (only), and returns a pair (loc, a) of the current
       location and the value a.  This is typically used to decorate
       abstract syntax tree nodes with location information, for use in
       subsequent error reports.

       [xLR loc_a] returns the location of the decorated value loc_a.

       [xL loc_a] returns the left end position of loc_a.

       [xR loc_a] returns the right end position of loc_a.

       [xxLR loc_a loc_b] returns the location extending from the left end
       of loc_a to the right end of loc_b.

       [xxRL loc_a loc_b] returns the location extending from the right end
       of loc_a to the left end of loc_b.
    *)

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Moscow ML 2.00