implement Sleep; include "sys.m";sys: Sys; include "draw.m"; Sleep: module{	init: fn(ctxt: ref Draw->Context, argv: list of string);}; init(nil: ref Draw->Context, argv: list of string){	sys = load Sys Sys->PATH;	if(sys == nil || argv == nil)		return;	argv = tl argv;	if(argv != nil && isvalid(hd argv)){		t := int hd argv;		if(t > 16r7fffffff / 1000)			t = 16r7fffffff / 1000;		sys->sleep(t * 1000);	} else {		sys->fprint(sys->fildes(2), "usage: sleep time\n");		raise "fail:usage";	}} isvalid(t: string): int{	l := len t;	if(l > 0 && (t[0] == '-' || t[0] == '+'))		x := 1;	else		x = 0;	ok := 0;	while(x < l) {		d := t[x];		if(d < '0' || d > '9')			return 0;		ok = 1;		x++;	}	return ok;}