/** Boucle while, while ( Exp !=0) { Exp }. */
public class ExpWhile extends Exp{
  public Exp e1, e2;
  public ExpWhile(Exp e1, Exp e2) { super(e1, e2); this.e1 = e1; this.e2 = e2; }
  public Integer eval(){
    Integer res = -1;
    while (e1.eval() != 0) res = e2.eval();
    return res;
  }
  public void accept(AstVisitor v) { v.visit(this); }
}