Strategy of `StructureOptimizer`.

According to the meaning of logical nodes(discussed in #15 ), the AST should be optimized by removing some non-terminal nodes. Code fragment implemented the strategy is as follow:

  SharedPtrNodeContainer optimized_children;
  for (auto child : node->children_) {
    child->Accept(this);
    // decide expand or not.
    bool child_is_logic_and =
        child->GetID() == kNonTermianlClassName.at(NonTerminalType::LOGIC_AND);
    bool child_is_logic_xor =
        child->GetID() == kNonTermianlClassName.at(NonTerminalType::LOGIC_XOR);
    bool child_is_logic_or =
        child->GetID() == kNonTermianlClassName.at(NonTerminalType::LOGIC_OR);
    bool equivalent = false;
    // 1. equivalent if they have the same id.
    if (node->GetID() == child->GetID()) {
      equivalent = true;
    }
    // 2. when child is one of (`LogicAnd`, `LogicXor`, `LogicOr`), and
    // child->GetSizeOfChildren() equals to 1, remove the child.
    if ((child_is_logic_and || child_is_logic_xor || child_is_logic_or)
        && child->GetSizeOfChildren() == 1) {
      equivalent = true;
    }
    // remove non-terminal based on `equivalent`.
    if (equivalent) {
      // same non-terminal nodes.
      optimized_children.insert(
          optimized_children.end(),
          children_of_child_.begin(), children_of_child_.end());
    } else {
      optimized_children.push_back(child);
    }
  }

And node type transformation:

void StructureOptimizer::ProcessNode(
    LogicXor::SharedPtr node) {
  RemoveDuplicatedNodes(node);
  // transfrom to `LogicAnd` when there's only one child.
  if (node->GetSizeOfChildren() == 1) {
    NodeTypeModifier<LogicAnd>::ChangeNonTerminalType(node);
  }
}

void StructureOptimizer::ProcessNode(
    LogicOr::SharedPtr node) {
  RemoveDuplicatedNodes(node);
  // transfrom to `LogicAnd` when there's only one child.
  if (node->GetSizeOfChildren() == 1) {
    NodeTypeModifier<LogicAnd>::ChangeNonTerminalType(node);
  }
}

huntzhan / clidoc

Strategy of `StructureOptimizer`. #18