yaccpar

unix v7是最后一个广泛发布的研究型UNIX版本

#
# define YYFLAG -1000
# define YYERROR goto yyerrlab
# define YYACCEPT return(0)
# define YYABORT return(1)

/*	parser for yacc output	*/

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

yyparse() {

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

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

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

	if( yydebug  ) printf( "state %d, char 0%o\n", yystate, yychar );
		if( ++yyps> &yys[YYMAXDEPTH] ) { 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 */

			while ( yyps >= yys ) {
			   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 */

			   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 ) printf("reduce %d\n",yyn);
		yyps -= yyr2[yyn];
		yypvt = yypv;
		yypv -= yyr2[yyn];
		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;  /* stack new state and value */

	}