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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. class Visitor;
  8.  
  9. class Node
  10. {
  11. public:
  12.   vector<Node*> children;
  13.   virtual ~Node() = default;
  14.   virtual void accept(Visitor&);
  15. };
  16.  
  17. class ANode : public Node
  18. {
  19. public:
  20.   virtual void accept(Visitor&);
  21.  
  22. };
  23. class BNode : public Node
  24. {
  25. public:
  26.   virtual void accept(Visitor&);
  27. };
  28. class CNode : public Node
  29. {
  30. public:
  31.   virtual void accept(Visitor&);
  32. };
  33.  
  34. //-- try inheritance
  35.  
  36. class SubBNode: public BNode
  37. {
  38. public:
  39.   virtual void accept(Visitor&);
  40. };
  41.  
  42. //--
  43.  
  44. class Visitor 
  45. {
  46.   public:
  47.   virtual void visit(Node& n);
  48.   virtual void visit(ANode& n);
  49.   virtual void visit(BNode& n);
  50.   virtual void visit(CNode& n);
  51.   virtual void visit(SubBNode& n);
  52. };
  53.  
  54.  
  55. //---------------------------------------------
  56.  
  57. void Node::accept(Visitor& v){
  58.   cout << __PRETTY_FUNCTION__ << endl;
  59.   v.visit(*this);
  60. }
  61. void ANode::accept(Visitor& v){
  62.   cout << __PRETTY_FUNCTION__ << endl;
  63.   v.visit(*this);
  64. }
  65. void BNode::accept(Visitor& v){
  66.   cout << __PRETTY_FUNCTION__ << endl;
  67.   v.visit(*this);
  68. }
  69. void CNode::accept(Visitor& v){
  70.   cout << __PRETTY_FUNCTION__ << endl;
  71.   v.visit(*this);
  72. }
  73. void SubBNode::accept(Visitor& v){
  74.   cout << __PRETTY_FUNCTION__ << endl;
  75.   v.visit(*this);
  76. }
  77. // -----
  78. void Visitor::visit(Node& n){
  79.   cout << __PRETTY_FUNCTION__ << "\t\tDEFAULT" << endl;
  80. }
  81. void Visitor::visit(ANode& n){
  82.   cout << __PRETTY_FUNCTION__ << "\t\tDEFAULT" << endl;
  83. }
  84. void Visitor::visit(BNode& n){
  85.   cout << __PRETTY_FUNCTION__ << "\t\tDEFAULT" << endl;
  86. }
  87. void Visitor::visit(CNode& n){
  88.   cout << __PRETTY_FUNCTION__ << "\t\tDEFAULT" << endl;
  89. }
  90. void Visitor::visit(SubBNode& n){
  91.   cout <<  __PRETTY_FUNCTION__ << "\t\tDEFAULT" << endl;
  92. }
  93.  
  94. template <typename F>
  95. class FunctorVisitor : public Visitor
  96. {
  97. public:
  98.     explicit FunctorVisitor(F& f) : f(f) {}
  99.  
  100.     virtual void visit(Node& n) override { f(n);}
  101.     virtual void visit(ANode& n) override { f(n);}
  102.     virtual void visit(BNode& n) override { f(n);}
  103.     virtual void visit(CNode& n) override { f(n);}
  104.     virtual void visit(SubBNode& n) override { f(n);}
  105. private:
  106.     F& f;
  107. };
  108.  
  109.  
  110. class CountVisitor
  111. {
  112. public:
  113.     void operator() (const Node& n) const {
  114.         cout << __PRETTY_FUNCTION__ << "\t\tDefault" << endl;
  115.     }
  116.     void operator() (const BNode& n) {
  117.         count++;
  118.         cout << __PRETTY_FUNCTION__ << "\t\tSPECIAL" << endl;
  119.     }
  120.  
  121.     int count = 0;
  122.     void print() const {
  123.         cout << "CountVisitor Found Bs: "<< count << endl;
  124.     }
  125. };
  126.  
  127. // ====================================================
  128.  
  129. int main() {
  130.     cout << "======FLAT TEST======" << endl;
  131.  
  132.     Node n;
  133.     ANode a;
  134.     BNode b1;
  135.     CNode c;
  136.     BNode b2;
  137.     SubBNode subB;
  138.  
  139.     vector<Node*> nodes = { &n, &a, &b1, &c, &b2, &subB };
  140.  
  141.     cout << "--DEFAULT--" << endl;
  142.     Visitor v1;
  143.     for( Node* n : nodes ){
  144.         n->accept(v1);
  145.     }
  146.  
  147.     cout << "--COUNT--" << endl;
  148.     CountVisitor cv1;
  149.     FunctorVisitor<CountVisitor> d(cv1);
  150.     for (Node* n : nodes){
  151.         n->accept(d);
  152.     }
  153.     cv1.print();
  154. }
  155.  
Success #stdin #stdout 0s 16072KB
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stdout
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======FLAT TEST======
--DEFAULT--
virtual void Node::accept(Visitor&)
virtual void Visitor::visit(Node&)		DEFAULT
virtual void ANode::accept(Visitor&)
virtual void Visitor::visit(ANode&)		DEFAULT
virtual void BNode::accept(Visitor&)
virtual void Visitor::visit(BNode&)		DEFAULT
virtual void CNode::accept(Visitor&)
virtual void Visitor::visit(CNode&)		DEFAULT
virtual void BNode::accept(Visitor&)
virtual void Visitor::visit(BNode&)		DEFAULT
virtual void SubBNode::accept(Visitor&)
virtual void Visitor::visit(SubBNode&)		DEFAULT
--COUNT--
virtual void Node::accept(Visitor&)
void CountVisitor::operator()(const Node&) const		Default
virtual void ANode::accept(Visitor&)
void CountVisitor::operator()(const Node&) const		Default
virtual void BNode::accept(Visitor&)
void CountVisitor::operator()(const BNode&)		SPECIAL
virtual void CNode::accept(Visitor&)
void CountVisitor::operator()(const Node&) const		Default
virtual void BNode::accept(Visitor&)
void CountVisitor::operator()(const BNode&)		SPECIAL
virtual void SubBNode::accept(Visitor&)
void CountVisitor::operator()(const BNode&)		SPECIAL
CountVisitor Found Bs: 3
https://ideone.com/ABSZbj
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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