#include <lib9.h>#include "regexp.h" /* substitute into one string using the matches from the last regexec() */extern	voidregsub(char *sp,	/* source string */	char *dp,	/* destination string */	Resub *mp,	/* subexpression elements */	int ms)		/* number of elements pointed to by mp */{	char *ssp;	int i; 	while(*sp != '\0'){		if(*sp == '\\'){			switch(*++sp){			case '0':			case '1':			case '2':			case '3':			case '4':			case '5':			case '6':			case '7':			case '8':			case '9':				i = *sp-'0';				if(mp[i].s.sp != 0 && mp!=0 && ms>i)					for(ssp = mp[i].s.sp;					     ssp < mp[i].e.ep;					     ssp++)						*dp++ = *ssp;				break;			case '\\':				*dp++ = '\\';				break;			case '\0':				sp--;				break;			default:				*dp++ = *sp;				break;			}		}else if(*sp == '&'){							if(mp[0].s.sp != 0 && mp!=0 && ms>0)			if(mp[0].s.sp != 0)				for(ssp = mp[0].s.sp;				     ssp < mp[0].e.ep; ssp++)					*dp++ = *ssp;		}else			*dp++ = *sp;		sp++;	}	*dp = '\0';}