cfg accepting

Language/public/ContextFreeAutomata.hpp

@@ -15,11 +15,79 @@ namespace tp {
 			ualni num = 0; // state to shift (shift action) or pop count (reduce action)
 		};
 
-		Buffer2D<Action> mTable;
+	public:
+		struct StackItem {
+			ualni state = 0;
+			tAlphabetType symbol;
+			Buffer<StackItem*> leafs;
+		};
+
+		struct AcceptResult {
+			bool accepted = false;
+			ualni advancedIdx = 0;
+			const StackItem* ast = nullptr;
+		};
 
 	public:
 		ContextFreeAutomata() = default;
 
+		AcceptResult accept(const tAlphabetType* stream, ualni size) {
+			mCurrentState = mStartState;
+			mStack.append(&mItems.append({ mCurrentState, {}, {} }));
+
+			ualni advancedIdx = 0;
+			while (advancedIdx < size) {
+				tAlphabetType& symbol = *(stream + advancedIdx);
+
+				const Action& action = mTable.get({ ualni(symbol), mCurrentState });
+
+				switch (action.type) {
+					case Action::TRAP: return { false, advancedIdx, nullptr };
+					case Action::REDUCE:
+						{
+							StackItem* newItem = &mItems.append({});
+							for (auto iter : Range<ualni>(action.num)) {
+								newItem->leafs.append(mStack.last());
+								mCurrentState = mStack.last()->state;
+								mStack.pop();
+							}
+
+							if (!mStack.size()) {
+								if (advancedIdx == size) {
+									return { true, advancedIdx, newItem };
+								} else {
+									return { false, advancedIdx, {} };
+								}
+							}
+
+							mStack.append(&mItems.append({ mCurrentState, {}, {} }));
+							break;
+						}
+					case Action::SHIFT:
+						{
+							mStack.last()->symbol = symbol;
+							mStack.append(&mItems.append({ mCurrentState, {}, {} }));
+							mCurrentState = action.num;
+							break;
+						}
+				}
+
+				advancedIdx++;
+			}
+
+			return { false, advancedIdx, nullptr };
+		}
+
+	public:
 		void construct(const FiniteStateAutomation<tAlphabetType, tStateType>& automata) {}
+
+	private:
+		Buffer2D<Action> mTable;
+
+		Buffer<StackItem> mItems;
+		Buffer<StackItem*> mStack;
+
+		ualni mStartState = 0;
+		ualni mCurrentState = 0;
 	};
 }