/*	parser for yacc output	*/

void *yyv[YYMAXDEPTH];	/*where the values are stored.  */
short yychar = -1; /* current input token number */
short yynerrs = 0;  /* number of errors */
short yyerrflag = 0;  /* error recovery flag */

Boolean yyparse(void) {

	short yys[YYMAXDEPTH];
	short yyj, yym;
	register TREE**yypvt;
	register short  *yyps, yyn;
	register TREE **yypv;
	register short *yyxi;

	yystate = 0;
	yychar = -1;
	yynerrs = 0;
	yyerrflag = 0;
	yyps= &yys[-1];
	yypv= (void *) &yyv[-1];

 yystack:    /* put a state and value onto the stack */

	if( yydebug  ) fprintf(obuf, "state %d, char 0%d\n", yystate, yychar );
	if( ++yyps> &yys[YYMAXDEPTH-1] ) {
		yyerror( "yacc stack overflow" );
		return(1);
		}
	*yyps = yystate;
	++yypv;
	*yypv = yyval;
 yynewstate:
	yyn = yypact[yystate];
	if( yyn<= YYFLAG ) goto yydefault; /* simple state */
	if( yychar<0 ) if( (yychar=yylex())<0 ) yychar=0;
	if( (yyn += yychar)<0 || yyn >= YYLAST ) goto yydefault;
	if( yychk[ yyn=yyact[ yyn ] ] == yychar ){ /* valid shift */
		yychar = -1;
		yyval = yylval;
		yystate = yyn;
		if( yyerrflag > 0 ) --yyerrflag;
		goto yystack;
		}
 yydefault:	/* default state action */
	if( (yyn=yydef[yystate]) == -2 ) {
		if( yychar<0 ) if( (yychar=yylex())<0 ) yychar = 0;
		/* look through exception table */
		for( yyxi=yyexca; (*yyxi!= (-1)) || (yyxi[1]!=yystate) ; yyxi += 2 ) ; /* VOID */
		while( *(yyxi+=2) >= 0 ){
			if( *yyxi == yychar ) break;
			}
		if( (yyn = yyxi[1]) < 0 ) return(0);   /* accept */
		}
	if( yyn == 0 ){ /* error */
		/* error ... attempt to resume parsing */
		switch( yyerrflag ){
		case 0:   /* brand new error */
			yyerror( "syntax error" );
yyerrlab:
			++yynerrs;
		case 1:
		case 2: /* incompletely recovered error ... try again */
			yyerrflag = 3;
			/* find a state where "error" is a legal shift action */
			
				 yyn = yypact[*yyps] + YYERRCODE;
				 if( yyn>= 0 && yyn < YYLAST && yychk[yyact[yyn]] == YYERRCODE ){
					 yystate = yyact[yyn];  /*simulate a shift of "error" */
					 goto yystack;
					 }
/*				 yyn = yypact[*yyps];
  the current yyps has no shift onn "error", pop stack 
			puts("EXPRESSION IS INCOMPLETE");
			   if( yydebug ) printf( "error recovery pops state %d, uncovers %d\n", *yyps, yyps[-1] );
			   --yyps;
			   --yypv;
			   }*/
/* there is no state on the stack with an error shift ... abort */
yyabort:
			return(1);

		case 3:  /* no shift yet; clobber input char */
			if( yydebug ) printf( "error recovery discards char %d\n", yychar );
			if( yychar == 0 ) goto yyabort; /* don't discard EOF, quit */
			yychar = -1;
			goto yynewstate;   /* try again in the same state */
			}
		}

	/* reduction by production yyn */
		if( yydebug ) fprintf(obuf,"reduce %d\n",yyn);
		yyps -= yyr2[yyn];
		yypvt = yypv;
		yypv -= yyr2[yyn];
		yyold = yyval;
		yyval = yypv[1];
		yym=yyn;
			/* consult goto table to find next state */
		yyn = yyr1[yyn];
		yyj = yypgo[yyn] + *yyps + 1;
		if( yyj>=YYLAST || yychk[ yystate = yyact[yyj] ] != -yyn )
			yystate = yyact[yypgo[yyn]];
		switch(yym){
			$A
			}
		goto yystack;
		}