YYParse.cod

(* Yacc parser template (TP Yacc V3.0), V1.2 6-17-91 AG *)

(* global definitions: *)
%%

var yylval : YYSType;

function yylex : Integer; forward;

function yyparse : Integer;

var yystate, yysp, yyn : Integer;
    yys : array [1..yymaxdepth] of Integer;
    yyv : array [1..yymaxdepth] of YYSType;
    yyval : YYSType;

procedure yyaction ( yyruleno : Integer );
  (* local definitions: *)
%%
begin
  (* actions: *)
  case yyruleno of
%%
  end;
end(*yyaction*);

(* parse table: *)
%%

const _error = 256; (* error token *)

function yyact(state, sym : Integer; var act : Integer) : Boolean;
  (* search action table *)
  var k : Integer;
  begin
    k := yyal[state];
    while (k<=yyah[state]) and (yya[k].sym<>sym) do inc(k);
    if k>yyah[state] then
      yyact := false
    else
      begin
        act := yya[k].act;
        yyact := true;
      end;
  end(*yyact*);

function yygoto(state, sym : Integer; var nstate : Integer) : Boolean;
  (* search goto table *)
  var k : Integer;
  begin
    k := yygl[state];
    while (k<=yygh[state]) and (yyg[k].sym<>sym) do inc(k);
    if k>yygh[state] then
      yygoto := false
    else
      begin
        nstate := yyg[k].act;
        yygoto := true;
      end;
  end(*yygoto*);

label parse, next, error, errlab, shift, reduce, accept, abort;

begin(*yyparse*)

  (* initialize: *)

  yystate := 0; yychar := -1; yynerrs := 0; yyerrflag := 0; yysp := 0;

{$ifdef yydebug}
  yydebug := true;
{$else}
  yydebug := false;
{$endif}

parse:

  (* push state and value: *)

  inc(yysp);
  if yysp>yymaxdepth then
    begin
      yyerror('yyparse stack overflow');
      goto abort;
    end;
  yys[yysp] := yystate; yyv[yysp] := yyval;

next:

  if (yyd[yystate]=0) and (yychar=-1) then
    (* get next symbol *)
    begin
      yychar := yylex; if yychar<0 then yychar := 0;
    end;

  if yydebug then writeln('state ', yystate, ', char ', yychar);

  (* determine parse action: *)

  yyn := yyd[yystate];
  if yyn<>0 then goto reduce; (* simple state *)

  (* no default action; search parse table *)

  if not yyact(yystate, yychar, yyn) then goto error
  else if yyn>0 then                      goto shift
  else if yyn<0 then                      goto reduce
  else                                    goto accept;

error:

  (* error; start error recovery: *)

  if yyerrflag=0 then yyerror('syntax error');

errlab:

  if yyerrflag=0 then inc(yynerrs);     (* new error *)

  if yyerrflag<=2 then                  (* incomplete recovery; try again *)
    begin
      yyerrflag := 3;
      (* uncover a state with shift action on error token *)
      while (yysp>0) and not ( yyact(yys[yysp], _error, yyn) and
                               (yyn>0) ) do
        begin
          if yydebug then
            if yysp>1 then
              writeln('error recovery pops state ', yys[yysp], ', uncovers ',
                      yys[yysp-1])
            else
              writeln('error recovery fails ... abort');
          dec(yysp);
        end;
      if yysp=0 then goto abort; (* parser has fallen from stack; abort *)
      yystate := yyn;            (* simulate shift on error *)
      goto parse;
    end
  else                                  (* no shift yet; discard symbol *)
    begin
      if yydebug then writeln('error recovery discards char ', yychar);
      if yychar=0 then goto abort; (* end of input; abort *)
      yychar := -1; goto next;     (* clear lookahead char and try again *)
    end;

shift:

  (* go to new state, clear lookahead character: *)

  yystate := yyn; yychar := -1; yyval := yylval;
  if yyerrflag>0 then dec(yyerrflag);

  goto parse;

reduce:

  (* execute action, pop rule from stack, and go to next state: *)

  if yydebug then writeln('reduce ', -yyn);

  yyflag := yyfnone; yyaction(-yyn);
  dec(yysp, yyr[-yyn].len);
  if yygoto(yys[yysp], yyr[-yyn].sym, yyn) then yystate := yyn;

  (* handle action calls to yyaccept, yyabort and yyerror: *)

  case yyflag of
    yyfaccept : goto accept;
    yyfabort  : goto abort;
    yyferror  : goto errlab;
  end;

  goto parse;

accept:

  yyparse := 0; exit;

abort:

  yyparse := 1; exit;

end(*yyparse*);