usr/src/cmd/lex/lib/yyless.c

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 = x;
while (lastch > ptr)
        yyunput(*--lastch);
*lastch = 0;
if (ptr >yytext)
        yyprevious = *--lastch;
yyleng = ptr-yytext;
}