Add commit 43aab01 of BenHanson/lexertl14 from github

YACReaderLibrary/lexertl/parser/tree/selection_node.hpp

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+// selection_node.hpp
+// Copyright (c) 2005-2018 Ben Hanson (http://www.benhanson.net/)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file licence_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+#ifndef LEXERTL_SELECTION_NODE_HPP
+#define LEXERTL_SELECTION_NODE_HPP
+
+#include "node.hpp"
+
+namespace lexertl
+{
+namespace detail
+{
+template<typename id_type>
+class basic_selection_node : public basic_node<id_type>
+{
+public:
+    using node = basic_node<id_type>;
+    using bool_stack = typename node::bool_stack;
+    using const_node_stack = typename node::const_node_stack;
+    using node_ptr_vector = typename node::node_ptr_vector;
+    using node_stack = typename node::node_stack;
+    using node_type = typename node::node_type;
+
+    basic_selection_node(observer_ptr<node> left_, observer_ptr<node> right_) :
+        node(left_->nullable() || right_->nullable()),
+        _left(left_),
+        _right(right_)
+    {
+        _left->append_firstpos(node::_firstpos);
+        _right->append_firstpos(node::_firstpos);
+        _left->append_lastpos(node::_lastpos);
+        _right->append_lastpos(node::_lastpos);
+    }
+
+    virtual ~basic_selection_node() override
+    {
+    }
+
+    virtual node_type what_type() const override
+    {
+        return node::SELECTION;
+    }
+
+    virtual bool traverse(const_node_stack &node_stack_,
+        bool_stack &perform_op_stack_) const override
+    {
+        perform_op_stack_.push(true);
+
+        switch (_right->what_type())
+        {
+        case node::SEQUENCE:
+        case node::SELECTION:
+        case node::ITERATION:
+            perform_op_stack_.push(false);
+            break;
+        default:
+            break;
+        }
+
+        node_stack_.push(_right);
+        node_stack_.push(_left);
+        return true;
+    }
+
+private:
+    observer_ptr<node> _left;
+    observer_ptr<node> _right;
+
+    virtual void copy_node(node_ptr_vector &node_ptr_vector_,
+        node_stack &new_node_stack_, bool_stack &perform_op_stack_,
+        bool &down_) const override
+    {
+        if (perform_op_stack_.top())
+        {
+            observer_ptr<node> rhs_ = new_node_stack_.top();
+
+            new_node_stack_.pop();
+
+            observer_ptr<node> lhs_ = new_node_stack_.top();
+
+            node_ptr_vector_.emplace_back
+                (std::make_unique<basic_selection_node>(lhs_, rhs_));
+            new_node_stack_.top() = node_ptr_vector_.back().get();
+        }
+        else
+        {
+            down_ = true;
+        }
+
+        perform_op_stack_.pop();
+    }
+
+    // No copy construction.
+    basic_selection_node(const basic_selection_node &) = delete;
+    // No assignment.
+    const basic_selection_node &operator =
+        (const basic_selection_node &) = delete;
+};
+}
+}
+
+#endif