1 files changed, 152 insertions, 0 deletions
diff --git a/c++/core/tree.h b/c++/core/tree.h
new file mode 100644
index 0000000..6ffd1f0
--- /dev/null
+++ b/c++/core/tree.h
@@ -0,0 +1,152 @@
+#pragma once
+
+#include <variant>
+#include <vector>
+
+#include "error.h"
+
+namespace saw {
+template<typename T>
+class tree_or;
+
+template<typename T>
+class tree final {
+private:
+	std::vector<tree_or<T>> children_;
+public:
+	tree() = default;
+	~tree() = default;
+
+	error_or<std::size_t> add(T leaf) {
+		std::size_t index = size();
+		try {
+			children_.push_back(std::move(leaf));
+		}catch(const std::exception& e){
+			(void)e;
+
+			return make_error<err::critical>();
+		}
+
+		return index;
+	}
+
+	error_or<std::size_t> add() {
+		std::size_t index = size();
+		try {
+			children_.push_back(tree{});
+		}catch(const std::exception& e){
+			(void)e;
+
+			return make_error<err::critical>();
+		}
+
+		return index;
+	}
+
+	std::size_t size() const {
+		return children_.size();
+	}
+
+	tree_or<T>& at(std::size_t i){
+		return children_.at(i);
+	}
+
+	const tree_or<T>& at(std::size_t i) const {
+		return children_.at(i);
+	}
+};
+
+template<typename T>
+class tree_or final {
+private:
+	using type = std::variant<tree<T>,T>;
+	type tov_;
+
+	friend class tree<T>;
+public:
+	tree_or():tov_{tree<T>{}}{}
+
+	tree_or(tree<T> nd):tov_{std::move(nd)}{}
+
+	tree_or(T val):tov_{std::move(val)}{}
+
+	template<typename NT>
+	bool is() const {
+		return std::holds_alternative<NT>(tov_);
+	}
+
+	bool is_tree() const {
+		return std::holds_alternative<tree>(tov_);
+	}
+
+	bool is_value() const {
+		return std::holds_alternative<T>(tov_);
+	}
+
+	template<typename NT>
+	NT& get() {
+		return std::get<NT>(tov_);
+	}
+	
+	template<typename NT>
+	const NT& get() const {
+		return std::get<NT>(tov_);
+	}
+
+	tree<T>& get_tree(){
+		return std::get<tree>(tov_);
+	}
+
+	const tree<T>& get_tree() const {
+		return std::get<tree>(tov_);
+	}
+
+	T& get_value(){
+		return std::get<T>(tov_);
+	}
+
+	const T& get_value() const {
+		return std::get<T>(tov_);
+	}
+
+	template<typename NT>
+	error_or<NT> extract(){
+		if(!is<NT>()){
+			return make_error<err::invalid_state>();
+		}
+		
+		NT nd = std::move(std::get<NT>(tov_));
+		tov_ = tree<T>{};
+
+		return nd;
+	}
+	
+	template<typename NT>
+	error_or<NT> replace(type nd){
+		auto eon = extract<NT>();
+		if(eon.is_error()){
+			return eon;
+		}
+
+		tov_ = std::move(nd);
+
+		return eon;
+	}
+
+	error_or<tree<T>> extract_tree() {
+		return extract<tree<T>>();
+	}
+
+	error_or<tree<T>> replace_tree(type nd){
+		return replace<tree<T>>(std::move(nd));
+	}
+
+	error_or<T> extract_value() {
+		return extract<T>();
+	}
+
+	error_or<T> replace_value(type nd){
+		return replace<T>(std::move(nd));
+	}
+};
+}