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  1. //chaining comparison object
  2. template<class T>
  3. class comparison {
  4.     const bool result;
  5.     const T& last;
  6. public:
  7.     comparison(const T& l, bool r=true) :result(r), last(l) {}
  8.     operator bool() const {return result;}
  9.     comparison operator<(const T& rhs) const {return comparison(rhs, (result && last<rhs));}
  10.     comparison operator<=(const T& rhs) const {return comparison(rhs, (result && last<=rhs));}
  11.     comparison operator>(const T& rhs) const {return comparison(rhs, (result && last>rhs));}
  12.     comparison operator>=(const T& rhs) const {return comparison(rhs, (result && last>=rhs));}
  13. };
  14.  
  15. //random object that has operator chaining built in
  16. struct a {
  17.     int val;
  18.     comparison<a> operator<(const a& rhs) const {return comparison<a>(rhs, val<rhs.val);}
  19.     comparison<a> operator<=(const a& rhs) const {return comparison<a>(rhs, val<=rhs.val);}
  20.     comparison<a> operator>(const a& rhs) const {return comparison<a>(rhs, val>rhs.val);}
  21.     comparison<a> operator>=(const a& rhs) const {return comparison<a>(rhs, val>=rhs.val);}
  22. };
  23.  
  24. #include <iostream>
  25. int main() {
  26.     a v0 = {0};
  27.     a v1 = {1};
  28.     a v2 = {2};
  29.     //testing of chained comparisons with builtin
  30.     std::cout << (v0<v1<v2) << '\n';
  31.     std::cout << (v0<v1>v2) << '\n';
  32.     std::cout << (v0>v1<v2) << '\n';
  33.     std::cout << (v0>v1>v2) << '\n';
  34.     //testing of chained comparisons with int
  35.     std::cout << (comparison<int>(0)<1<2) << '\n';
  36.     std::cout << (comparison<int>(0)<1>2) << '\n';
  37.     std::cout << (comparison<int>(0)>1<2) << '\n';
  38.     std::cout << (comparison<int>(0)>1>2) << '\n';
  39. }
  40.  
Success #stdin #stdout 0s 2884KB
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https://ideone.com/awrmK
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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