c++ - 在C++中平均一组复数的正确方法是什么？

Question

我继承了一些C++代码，需要平均一些复数。给定一个集合，它会将那些将条件传递给累加器的值相加，然后除以所添加值的数量。
使用gcc(当前为gcc 8)，如果我使用独立的template argument deduction/substitution failed，我会得到operator/，但它与std::complex::operator/=可以正常工作。对于后续维护者来说，这样的细微差别似乎很脆弱。
那么获得复数平均值的正确方法是什么？
语言仅部分支持按整数类型对复数进行除法是否合理？

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

(代表错误，出于好奇)

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

不确定最合适的除法方法，但是如果仔细检查operator/和operator/=的所有参数，则会发现:

operator/接受std::complex<T>或T。

因此，如果您使用double创建了原始复合体，则它仅应采用另一个值为double或complex<double>的值。

实际上，取决于您使用的编译器，clang向上直接给出了invalid operands to binary expression ('std::complex<double>' and 'int')错误

operator/=接受std::complex<T>或T，同时还具有float，double和long double的专门化功能。

这意味着传递给operator/=的任何内容都将进行更改，以将其隐式转换为float可以执行的double，long double或int。