set letters="ABCDEFGHIJKLMNOPQRSTUVWXYZ"::split();

func caesar(text,shift:number=1){
	set res:string="";
	for(i=0;?text-1;1){
		set t=text::at(i);
		set n=(letters::find(t::upper())+shift)%?letters;
		while(n<0){
			n=?letters+n;
		}
		set l=letters[n];
		(t::upper()==t)|=>l=l::lower()
		res+=l;
	}
	send res;
}

func decode(text,shift:number=1){
	set res:string="";
	for(i=0;?text-1;1){
		set t=text::at(i);
		set n=(letters::find(t::upper())-shift)%?letters;
		while(n<0){
			n=?letters+n;
		}
		set l=letters[n];
		(t::upper()==t)|=>l=l::lower()
		res+=l;
	}
	send res;
}

set e=caesar("Hi",20);
set d=decode(e,20);

log(e);
log(d);