xref: /original-bsd/old/yacc/old.yaccpar (revision 334a33f4)
1#ifndef lint
2static char yaccpar_sccsid[] = "@(#)old.yaccpar	4.1	(Berkeley)	02/11/83";
3#endif not lint
4
5#
6# define YYFLAG -1000
7# define YYERROR goto yyerrlab
8# define YYACCEPT return(0)
9# define YYABORT return(1)
10
11/*	parser for yacc output	*/
12
13#ifdef YYDEBUG
14int yydebug = 0; /* 1 for debugging */
15#endif
16YYSTYPE yyv[YYMAXDEPTH]; /* where the values are stored */
17int yychar = -1; /* current input token number */
18int yynerrs = 0;  /* number of errors */
19short yyerrflag = 0;  /* error recovery flag */
20
21yyparse() {
22
23	short yys[YYMAXDEPTH];
24	short yyj, yym;
25	register YYSTYPE *yypvt;
26	register short yystate, *yyps, yyn;
27	register YYSTYPE *yypv;
28	register short *yyxi;
29
30	yystate = 0;
31	yychar = -1;
32	yynerrs = 0;
33	yyerrflag = 0;
34	yyps= &yys[-1];
35	yypv= &yyv[-1];
36
37 yystack:    /* put a state and value onto the stack */
38
39#ifdef YYDEBUG
40	if( yydebug  ) printf( "state %d, char 0%o\n", yystate, yychar );
41#endif
42		if( ++yyps> &yys[YYMAXDEPTH] ) { yyerror( "yacc stack overflow" ); return(1); }
43		*yyps = yystate;
44		++yypv;
45		*yypv = yyval;
46
47 yynewstate:
48
49	yyn = yypact[yystate];
50
51	if( yyn<= YYFLAG ) goto yydefault; /* simple state */
52
53	if( yychar<0 ) if( (yychar=yylex())<0 ) yychar=0;
54	if( (yyn += yychar)<0 || yyn >= YYLAST ) goto yydefault;
55
56	if( yychk[ yyn=yyact[ yyn ] ] == yychar ){ /* valid shift */
57		yychar = -1;
58		yyval = yylval;
59		yystate = yyn;
60		if( yyerrflag > 0 ) --yyerrflag;
61		goto yystack;
62		}
63
64 yydefault:
65	/* default state action */
66
67	if( (yyn=yydef[yystate]) == -2 ) {
68		if( yychar<0 ) if( (yychar=yylex())<0 ) yychar = 0;
69		/* look through exception table */
70
71		for( yyxi=yyexca; (*yyxi!= (-1)) || (yyxi[1]!=yystate) ; yyxi += 2 ) ; /* VOID */
72
73		while( *(yyxi+=2) >= 0 ){
74			if( *yyxi == yychar ) break;
75			}
76		if( (yyn = yyxi[1]) < 0 ) return(0);   /* accept */
77		}
78
79	if( yyn == 0 ){ /* error */
80		/* error ... attempt to resume parsing */
81
82		switch( yyerrflag ){
83
84		case 0:   /* brand new error */
85
86			yyerror( "syntax error" );
87		yyerrlab:
88			++yynerrs;
89
90		case 1:
91		case 2: /* incompletely recovered error ... try again */
92
93			yyerrflag = 3;
94
95			/* find a state where "error" is a legal shift action */
96
97			while ( yyps >= yys ) {
98			   yyn = yypact[*yyps] + YYERRCODE;
99			   if( yyn>= 0 && yyn < YYLAST && yychk[yyact[yyn]] == YYERRCODE ){
100			      yystate = yyact[yyn];  /* simulate a shift of "error" */
101			      goto yystack;
102			      }
103			   yyn = yypact[*yyps];
104
105			   /* the current yyps has no shift onn "error", pop stack */
106
107#ifdef YYDEBUG
108			   if( yydebug ) printf( "error recovery pops state %d, uncovers %d\n", *yyps, yyps[-1] );
109#endif
110			   --yyps;
111			   --yypv;
112			   }
113
114			/* there is no state on the stack with an error shift ... abort */
115
116	yyabort:
117			return(1);
118
119
120		case 3:  /* no shift yet; clobber input char */
121
122#ifdef YYDEBUG
123			if( yydebug ) printf( "error recovery discards char %d\n", yychar );
124#endif
125
126			if( yychar == 0 ) goto yyabort; /* don't discard EOF, quit */
127			yychar = -1;
128			goto yynewstate;   /* try again in the same state */
129
130			}
131
132		}
133
134	/* reduction by production yyn */
135
136#ifdef YYDEBUG
137		if( yydebug ) printf("reduce %d\n",yyn);
138#endif
139		yyps -= yyr2[yyn];
140		yypvt = yypv;
141		yypv -= yyr2[yyn];
142		yyval = yypv[1];
143		yym=yyn;
144			/* consult goto table to find next state */
145		yyn = yyr1[yyn];
146		yyj = yypgo[yyn] + *yyps + 1;
147		if( yyj>=YYLAST || yychk[ yystate = yyact[yyj] ] != -yyn ) yystate = yyact[yypgo[yyn]];
148		switch(yym){
149			$A
150		}
151		goto yystack;  /* stack new state and value */
152
153	}
154