@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ExpressionNode that = (ExpressionNode) o;

        if (left != null ? !left.equals(that.left) : that.left != null) return false;
        if (right != null ? !right.equals(that.right) : that.right != null) return false;
        if (token != null ? !token.equals(that.token) : that.token != null) return false;

        return true;
    }