C++ 表达式树遍历以就地将表达式更改为 NNF

我想将表达式转换为否定范式。为此，我有一个使用智能指针的二叉表达式树。问题在于，当双否定出现在二进制表达式中时，删除双否定不起作用，尽管函数removeDoubleNot()是在正确的时间调用的。因此，例如 ¬(A∨¬B( 变为 ¬A∧¬¬B 而不是 ¬A∧B，但它仅适用于 ¬¬B。我认为错误在evaluate()但我还找不到它。也许递归是错误的？

// It is assumed that all Expressions are valid
std::shared_ptr<Expression> NNF::removeDoubleNot(std::shared_ptr<Not> expr) {
// Left is a Not -> remove both Nots
if (auto node = dynamic_cast<Not *>(expr->getLeft().get()))
return node->getLeft();
return expr;
}
std::shared_ptr<Expression> NNF::applyDeMorgan(std::shared_ptr<Not> expr) {
// And
if (auto node = dynamic_cast<And *>(expr->getLeft().get())) {
auto newLeft = std::make_shared<Not>(node->getLeft());
auto newRight = std::make_shared<Not>(node->getRight());
return std::make_shared<Or>(newLeft, newRight);
}
// Or
if (auto node = dynamic_cast<Or *>(expr->getLeft().get())) {
auto newLeft = std::make_shared<Not>(node->getLeft());
auto newRight = std::make_shared<Not>(node->getRight());
return std::make_shared<And>(newLeft, newRight);
}
return expr;
}
std::shared_ptr<Expression> NNF::removeImplication(const std::shared_ptr<Implication> &expr) {
auto newLeft = std::make_shared<Not>(expr->getLeft());
auto newRight = expr->getRight();
return std::make_shared<Or>(newLeft, newRight);
}
std::shared_ptr<Expression> NNF::moveNegationInwards(const std::shared_ptr<Not> &notExpr) {     
expr = applyDeMorgan(node);
if (auto node = std::dynamic_pointer_cast<Not>(expr))
expr = removeDoubleNot(node);
return expr;
}
std::shared_ptr<Expression> NNF::evaluate(std::shared_ptr<Expression> expr) {
if (expr == nullptr)
return nullptr;
// Implication
if(auto node = std::dynamic_pointer_cast<Implication>(expr)){
auto ret = removeImplication(node);
evaluate(ret->getLeft());
evaluate(ret->getRight());
return ret;
}
// Other binary than implication
if(auto node = dynamic_cast<Binary*>(expr.get())){
evaluate(node->getLeft());
evaluate(node->getRight());
return expr;
}
// Not
if(auto node = std::dynamic_pointer_cast<Not>(expr)) {
auto ret =  moveNegationInwards(node);
evaluate(ret->getLeft());
evaluate(ret->getRight());
return ret;
}
return expr;
}