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  1. #include <utility> // move
  2. #include <iostream>
  3.  
  4. using std::move;
  5. using std::ostream;
  6.  
  7. struct Matrix {
  8.     int d; /* = 0, not yet implemented in gcc-4.7.0 */
  9.     Matrix(int e) : d{e} {}
  10.  
  11. // construction, copy, assign
  12.     Matrix() = default;
  13.     Matrix(const Matrix&) = default;
  14.     Matrix& operator=(const Matrix&) = default;
  15.  
  16. // move, move-assign (no no magic in this example)
  17.     Matrix(Matrix&&) = default;
  18.     //Matrix& operator=(Matrix&&) = default;
  19.     Matrix& operator=(Matrix&& o) { swap(*this,o); return *this; };
  20.  
  21. // friendly STL helper
  22.     friend void swap(Matrix& a, Matrix& b) /* noexcept */ { std::swap(a.d, b.d); }
  23.  
  24. // imm ops
  25.     void operator+=(const Matrix& o) { d+=o.d; }
  26.     void operator*=(const Matrix& o) { d*=o.d; }
  27.  
  28. // 2ary ops
  29.     friend Matrix operator+(const Matrix &a, Matrix &&b     ) { b+=a; return move(b); }
  30.     friend Matrix operator+(Matrix &&a,      const Matrix &b) { a+=b; return move(a); }
  31.     friend Matrix operator+(const Matrix &a, Matrix v)        { v+=a; return v; }
  32.     friend Matrix operator+(Matrix &&a,      Matrix &&b)      { a+=b; return move(a); }
  33.  
  34.     friend Matrix operator*(const Matrix &a, Matrix &&b     ) { b*=a; return move(b); }
  35.     friend Matrix operator*(Matrix &&a,      const Matrix &b) { a*=b; return move(a); }
  36.     friend Matrix operator*(const Matrix &a, Matrix v)        { v*=a; return v; }
  37.     friend Matrix operator*(Matrix &&a,      Matrix &&b)      { a*=b; return move(a); }
  38.  
  39. // demo helper
  40.     friend ostream& operator<<(ostream&os, const Matrix& m)
  41.     { return os << m.d; }
  42.  
  43. };
  44.  
  45.  
  46. int main()
  47. {
  48.     Matrix a{2},b{3},c{4},d{5};
  49.     Matrix x = a*b + c*d; // 2*3+4*5 = 6+20 = 26
  50.  
  51.     std::cout << x << std::endl;
  52. }
  53.  
Success #stdin #stdout 0s 2828KB
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Standard input is empty
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26
https://ideone.com/KqPjw
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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