在 C++ 中平均一組復數的正確方法是什么？

Question

我繼承了一些需要平均一些復數的 C++ 代碼。 給定一個集合，它將那些傳遞條件的值添加到累加器，然后除以添加的值的數量。

使用 gcc（當前為 gcc 8）如果我使用獨立operator/ ，我會得到template argument deduction/substitution failed ，但它與std::complex::operator/=一起工作正常。 這種細微差別對於后續維護者來說似乎很脆弱。

那么獲得復數平均值的正確方法是什么？

該語言僅部分支持復數除以整數類型是否合理？

std::complex<double> A[32] = { /* initialization left to the reader */ };
int count = 0;

std::complex<double> sum;
for (auto i = 0; i < 32; ++i) {
   if ( i % 2 ) { // arbitrary condition, not important
      sum += A[i];
      ++count;
   }
}

auto avg = sum / count; // this is ambiguous
sum /= count;           // this is not

（代表性錯誤，好奇）

main.cpp: In function ‘int main()’:
main.cpp:16:16: error: no match for ‘operator/’ (operand types are ‘std::complex<double>’ and ‘int’)
 auto avg = sum / count; // this is ambiguous
            ~~~~^~~~~~~
In file included from main.cpp:2:0:
/usr/include/c++/7/complex:434:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const _Tp&, const std::complex<_Tp>&)
     operator/(const _Tp& __x, const complex<_Tp>& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:434:5: note:   template argument deduction/substitution failed:
main.cpp:16:18: note:   mismatched types ‘const std::complex<_Tp>’ and ‘int’
 auto avg = sum / count; // this is ambiguous
                  ^~~~~
In file included from main.cpp:2:0:
/usr/include/c++/7/complex:425:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const std::complex<_Tp>&, const _Tp&)
     operator/(const complex<_Tp>& __x, const _Tp& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:425:5: note:   template argument deduction/substitution failed:
main.cpp:16:18: note:   deduced conflicting types for parameter ‘const _Tp’ (‘double’ and ‘int’)
 auto avg = sum / count; // this is ambiguous
                  ^~~~~
In file included from main.cpp:2:0:
/usr/include/c++/7/complex:416:5: note: candidate: template<class _Tp> std::complex<_Tp> std::operator/(const std::complex<_Tp>&, const std::complex<_Tp>&)
     operator/(const complex<_Tp>& __x, const complex<_Tp>& __y)
     ^~~~~~~~
/usr/include/c++/7/complex:416:5: note:   template argument deduction/substitution failed:
main.cpp:16:18: note:   mismatched types ‘const std::complex<_Tp>’ and ‘int’
 auto avg = sum / count; // this is ambiguous
                  ^~~~~

Answer 1

不確定對其進行除法的最正確方法是什么，但是如果您查看operator/和operator/=所有參數，您會注意到：

• operator/接受std::complex<T>或T 。

  • 因此，如果您使用double創建了原始復合體，那么它應該只接受另一個值為double或complex<double> 。
  • 事實上，取決於你使用的編譯器， clang直接給了invalid operands to binary expression ('std::complex<double>' and 'int')錯誤

• operator/=接受std::complex<T>或T ，同時也特化了float 、 double和long double 。

  • 這意味着傳遞給operator/=任何內容都會被隱式轉換為float 、 double或long double ，而int可以這樣做。