Set the boolean b to true if the set x contains the element e, false otherwise.
b = x.find(e) != x.end();
b = x.Contains(e);
var b = x.contains(e);
b = x(e)
b := x[e]
_, b := x[e]
import Data.Set (member)
b = e `member` x
let b = x.has(e);
boolean b = x.contains(e);
(setf b (not (null (member e x))))
b := e in x;
$b = $x{$e};
b = e in x
b = x.include? e
let b = x.contains(&e);
No security, no password. Other people might choose the same nickname.