yyless.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

/*	@(#)yyless.c	4.1	12/25/82	*/

yyless(x)
{
extern char yytext[];
register char *lastch, *ptr;
extern int yyleng;
extern int yyprevious;
lastch = yytext+yyleng;
if (x>=0 && x <= yyleng)
	ptr = x + yytext;
else
	ptr = (char *)x;
while (lastch > ptr)
	yyunput(*--lastch);
*lastch = 0;
if (ptr >yytext)
	yyprevious = *--lastch;
yyleng = ptr-yytext;
}