public Compound(Istmt first, Istmt second)
{
this.first = first;
this.second = second;
}
public If(Exp e, Istmt t, Istmt el)
{
this.e = e;
this.thenS = t;
this.elseS = el;
}
public void oneStep()
{
Istmt s = stk.pop();
s.execute(this);
}
