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  1. #include <iostream>
  2.  
  3. using namespace std;
  4.  
  5. class ShapeVisitor;
  6.  
  7. struct Shape {
  8.     virtual void accept(ShapeVisitor& v) = 0;
  9.     virtual bool overlaps(Shape& other) = 0;
  10. };
  11.  
  12. class Circle;
  13. class Square;
  14.  
  15. struct ShapeVisitor {
  16.     virtual void visitCircle(Circle& c) = 0;
  17.     virtual void visitSquare(Square& s) = 0;
  18. };
  19.  
  20. bool checkOverlap(Square& s, Circle& c) {
  21.     cout << "Checking if square overlaps circle" << endl;
  22.     return false;
  23. }
  24. bool checkOverlap(Square& a, Square& b) {
  25.     cout << "Checking if square overlaps square" << endl;
  26.     return false;
  27. }
  28. bool checkOverlap(Circle& a, Circle& b) {
  29.     cout << "Checking if circle overlaps circle" << endl;
  30.     return false;
  31. }
  32.  
  33. class Square : public Shape {
  34.     struct OverlapVisitor : public ShapeVisitor {
  35.         OverlapVisitor(Square& _my) : result(false), my(_my) {}
  36.         virtual void visitCircle(Circle& c) {
  37.             result = checkOverlap(my, c);
  38.         }
  39.         virtual void visitSquare(Square& s) {
  40.             result = checkOverlap(my, s);
  41.         }
  42.         bool result;
  43.         Square& my;
  44.     };
  45. public:
  46.     virtual void accept(ShapeVisitor& v) {
  47.         v.visitSquare(*this);
  48.     }
  49.     virtual bool overlaps(Shape& other) {
  50.         OverlapVisitor v(*this);
  51.         other.accept(v);
  52.         return v.result;
  53.     }
  54. };
  55.  
  56. class Circle : public Shape {
  57.     struct OverlapVisitor : public ShapeVisitor {
  58.         OverlapVisitor(Circle& _my) : result(false), my(_my) {}
  59.         virtual void visitCircle(Circle& c) {
  60.             result = checkOverlap(my, c);
  61.         }
  62.         virtual void visitSquare(Square& s) {
  63.             result = checkOverlap(s, my);
  64.         }
  65.         bool result;
  66.         Circle& my;
  67.     };
  68. public:
  69.     virtual void accept(ShapeVisitor& v) {
  70.         v.visitCircle(*this);
  71.     }
  72.     virtual bool overlaps(Shape& other) {
  73.         OverlapVisitor v(*this);
  74.         other.accept(v);
  75.         return v.result;
  76.     }
  77. };
  78.  
  79. int main() {
  80.     Square s;
  81.     Circle c;
  82.     s.overlaps(c);
  83.     s.overlaps(s);
  84.     c.overlaps(s);
  85.     c.overlaps(c);
  86.     return 0;
  87. }
Success #stdin #stdout 0s 2856KB
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stdin 
Standard input is empty
stdout 
Checking if square overlaps circle
Checking if square overlaps square
Checking if square overlaps circle
Checking if circle overlaps circle
https://ideone.com/Q2x90D
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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