(* The lexer generator. Command-line parsing and expansion of abbreviations *) local open Lexing Parsing Miscsys;open Syntax Scanner Grammar Lexgen Output;open Fnlibin(* Lexer of stream *) fun createLexerStream (is : BasicIO.instream) =  Lexing.createLexer (fn buff => fn n => Nonstdio.buff_input is buff 0 n); fun expandRe defining name ls =    let fun expRe (Name s) =	    (lookup s ls	     handle Subscript => 		 (output(std_err, 			 if defining andalso s = name then 			     "Illegal recursive let-definition: "			 else "Undefined let-name: ");		  output(std_err, s); output(std_err,"\n\n");		  flush_out std_err;		  BasicIO.exit 2))	  | expRe (Sequence(r1,r2))     = Sequence (expRe r1, expRe r2)	  | expRe (Alternative (r1,r2)) = Alternative (expRe r1, expRe r2)	  | expRe (Repetition r)        = Repetition (expRe r)	  | expRe x                     = x    in expRe end fun expandLet (name, re) ls =     (name, expandRe true name ls re) :: ls  fun expandRule ls (name,rl) =    (name, List.map (fn (r, loc) => (expandRe false name ls r, loc)) rl) fun main () =  let val () =        if Vector.length command_line <> 2 then          (output(std_err, "Usage: mosmllex <input file>\n");           flush_out std_err;           BasicIO.exit 2)        else ()      val source_name = Vector.sub(command_line, 1)      val dest_name =        if Filename.check_suffix source_name ".lex" then          Filename.chop_suffix source_name ".lex" ^ ".sml"        else          source_name ^ ".sml"       val () = (is := open_in_bin source_name)      val () = (os := open_out dest_name)      val lexbuf =        createLexerStream (!is)      val Lexdef(header,lets,rules) =        lexer_definition Scanner.main lexbuf        handle          ParseError x =>            (output(std_err, "Syntax error around char ");             output(std_err, makestring (getLexemeStart lexbuf));             output(std_err, ".\n"); flush_out std_err;             BasicIO.exit 2)        | Scan_aux.Lexical_error s =>            (output(std_err, "Lexical error around char ");             output(std_err, makestring (getLexemeStart lexbuf));             output(std_err, ": ");             output(std_err, s);             output(std_err, ".\n"); flush_out std_err;             BasicIO.exit 2)      val nlets = foldL expandLet [] lets      val nrules = List.map (expandRule nlets) rules      val dfa as (init, states, acts) = make_dfa nrules   in    output_lexdef header dfa;    close_in (!is);    close_out (!os);    BasicIO.exit 0  end; val () = Printexc.f main ();end