private Variable(vBase v) { x = v; }
public Variable(string s) { x = new vString(s); }
public Variable(function f) { x = new vFunction(f); }
public Variable(int i) { x = new vInt(i); }
public Variable(bool b) { x = new vInt(b ? 1 : 0); }
public void substitution(Variable v) { x = x.substitution(v); }
public Variable() { x = new vObject(); }
public void assignment(Variable v) { x = v.x.clone(); }