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%{
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#include	"grep.h"
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%}
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%union
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{
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	int	val;
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	char*	str;
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	Re2	re;
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}
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%type	<re>	expr prog
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%type	<re>	expr0 expr1 expr2 expr3 expr4
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%token	<str>	LCLASS
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%token	<val>	LCHAR
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%token		LLPAREN LRPAREN LALT LSTAR LPLUS LQUES
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%token		LBEGIN LEND LDOT LBAD LNEWLINE
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%%
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prog:	/* empty */
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	{
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		yyerror("empty pattern");
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	}
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|	expr newlines
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	{
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		$$.beg = ral(Tend);
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		$$.end = $$.beg;
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		$$ = re2cat(re2star(re2or(re2char(0x00, '\n'-1), re2char('\n'+1, 0xff))), $$);
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		$$ = re2cat($1, $$);
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		$$ = re2cat(re2star(re2char(0x00, 0xff)), $$);
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		topre = $$;
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	}
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expr:
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	expr0
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|	expr newlines expr0
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	{
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		$$ = re2or($1, $3);
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	}
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expr0:
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	expr1
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|	LSTAR { literal = 1; } expr1
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	{
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		$$ = $3;
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	}
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expr1:
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	expr2
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|	expr1 LALT expr2
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	{
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		$$ = re2or($1, $3);
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	}
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expr2:
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	expr3
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|	expr2 expr3
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	{
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		$$ = re2cat($1, $2);
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	}
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expr3:
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	expr4
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|	expr3 LSTAR
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	{
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		$$ = re2star($1);
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	}
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|	expr3 LPLUS
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	{
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		$$.beg = ral(Talt);
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		patchnext($1.end, $$.beg);
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		$$.beg->alt = $1.beg;
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		$$.end = $$.beg;
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		$$.beg = $1.beg;
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	}
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|	expr3 LQUES
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	{
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		$$.beg = ral(Talt);
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		$$.beg->alt = $1.beg;
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		$$.end = $1.end;
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		appendnext($$.end,  $$.beg);
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	}
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expr4:
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	LCHAR
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	{
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		$$.beg = ral(Tclass);
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		$$.beg->lo = $1;
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		$$.beg->hi = $1;
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		$$.end = $$.beg;
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	}
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|	LBEGIN
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	{
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		$$.beg = ral(Tbegin);
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		$$.end = $$.beg;
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	}
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|	LEND
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	{
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		$$.beg = ral(Tend);
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		$$.end = $$.beg;
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	}
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|	LDOT
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	{
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		$$ = re2class("^\n");
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	}
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|	LCLASS
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	{
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		$$ = re2class($1);
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	}
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|	LLPAREN expr1 LRPAREN
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	{
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		$$ = $2;
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	}
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newlines:
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	LNEWLINE
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|	newlines LNEWLINE
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%%
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void
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yyerror(char *e, ...)
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{
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	va_list args;
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	fprint(2, "grep: ");
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	if(filename)
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		fprint(2, "%s:%ld: ", filename, lineno);
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	else if (pattern)
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		fprint(2, "%s: ", pattern);
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	va_start(args, e);
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	vfprint(2, e, args);
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	va_end(args);
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	fprint(2, "\n");
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	exits("syntax");
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}
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long
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yylex(void)
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{
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	char *q, *eq;
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	int c, s;
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	if(peekc) {
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		s = peekc;
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		peekc = 0;
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		return s;
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	}
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	c = getrec();
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	if(literal) {
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		if(c != 0 && c != '\n') {
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			yylval.val = c;
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			return LCHAR;
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		}
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		literal = 0;
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	}
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	switch(c) {
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	default:
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		yylval.val = c;
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		s = LCHAR;
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		break;
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	case '\\':
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		c = getrec();
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		yylval.val = c;
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		s = LCHAR;
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		if(c == '\n')
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			s = LNEWLINE;
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		break;
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	case '[':
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		goto getclass;
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	case '(':
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		s = LLPAREN;
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		break;
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	case ')':
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		s = LRPAREN;
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		break;
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	case '|':
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		s = LALT;
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		break;
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	case '*':
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		s = LSTAR;
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		break;
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	case '+':
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		s = LPLUS;
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		break;
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	case '?':
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		s = LQUES;
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		break;
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	case '^':
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		s = LBEGIN;
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		break;
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	case '$':
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		s = LEND;
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		break;
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	case '.':
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		s = LDOT;
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		break;
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	case 0:
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		peekc = -1;
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	case '\n':
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		s = LNEWLINE;
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		break;
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	}
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	return s;
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getclass:
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	q = u.string;
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	eq = q + nelem(u.string) - 5;
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	c = getrec();
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	if(c == '^') {
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		q[0] = '^';
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		q[1] = '\n';
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		q[2] = '-';
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		q[3] = '\n';
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		q += 4;
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		c = getrec();
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	}
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	for(;;) {
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		if(q >= eq)
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			error("class too long");
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		if(c == ']' || c == 0)
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			break;
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		if(c == '\\') {
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			*q++ = c;
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			c = getrec();
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			if(c == 0)
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				break;
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		}
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		*q++ = c;
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		c = getrec();
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	}
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	*q = 0;
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	if(c == 0)
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		return LBAD;
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	yylval.str = u.string;
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	return LCLASS;
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}