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  1. #include <iostream>
  2.  
  3. struct foo {
  4.  
  5.    struct IncrementMinder
  6.    {
  7.       IncrementMinder(foo* fPtr) : fPtr_(fPtr) {}
  8.       ~IncrementMinder() { ++(*fPtr_); }
  9.       foo* fPtr_;
  10.    };
  11.  
  12.    foo(int val) : value(val) {}
  13.  
  14.    // Not correct.
  15.    // const foo& operator++(int) {
  16.    foo operator++(int) {
  17.       IncrementMinder minder(this);
  18.       return *this;
  19.       // Destructor of minder takes care of ++(*this)
  20.    }
  21.  
  22.    foo& operator++() {
  23.       ++value;
  24.       return *this;
  25.    }
  26.  
  27.    operator int() {
  28.       return 0;
  29.    }
  30.  
  31.    int value;
  32.  
  33.  
  34. } bar{20};
  35.  
  36. void f(const foo& bar) { std::cout << "bar.value: " << bar.value << "\n"; }
  37.  
  38. int main()
  39. {
  40.    f(bar);
  41.  
  42.    std::cout << "Using post-increment...\n";
  43.  
  44.    f(bar++);
  45.    f(bar);;
  46.  
  47.    std::cout << "Using pre-increment...\n";
  48.  
  49.    f(++bar);
  50.    f(bar);
  51. }
  52.  
Success #stdin #stdout 0s 15232KB
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Standard input is empty
stdout
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bar.value: 20
Using post-increment...
bar.value: 20
bar.value: 21
Using pre-increment...
bar.value: 22
bar.value: 22
https://ideone.com/LrnTGy
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
secret

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