如何在类模板的成员函数中正确调用函数对象？正在生成 Visual Studio 编译器错误 C2440

这是在这里找到的这个问题的后续！

现在，我能够实例化对象。我现在收到一个Visual Studio C2440编译器错误...

在模板化之前的原始代码中，我有一组成员函数，用于处理std::function<double(double)>成员对象，如下所示：

struct SomeStruct {
double a_;
double b_;
SomeStruct(double a, double b) : a_{a}, b_{b} {}
};
class SomeClass {
private:
SomeStruct fields_;
size_t n_;
std::function<double(double)> func_;
public:
SomeClass(SomeStruct fields, size_t n, std::function<double(double)> func) :
fields_{fields}, n_{n}, func_{func}
{}
double evaluate() {
auto distance = fields_.a_ - fields_.b_;  
auto dx = distance / n_;
return calculate(dx, fields_);
}
private:
double calculate(double dx, const SomeStruct& someStruct) {
double result = 0;
for (size_t i = 0; i < n_; ++i) {
auto dy = func_(someStruct.a_ + i * dx);
auto area = dy * dx;
result += area;
}
return result;
}
};

现在我的类看起来像这样：

template<typename Field>
struct SomeStruct {
Field a_;
Field b_;
constexpr SomeStruct(Field a, Field b) : a_{a}, b_{b} {}
};
template<typename FieldType, typename ValueType, typename Func>
class SomeClass {
private:
SomeStruct<FieldType> fields_;
size_t n_;
Func func_; 
public:
SomeClass(SomeStruct<FieldType> fields, size_t n, Func func) :
fields_{fields}, n_{n}, func_{func}
{}
constexpr ValueType evaluate() {
auto distance = fields_.a_ - fields_.b_;       
auto dx = distance / n_;              
return calculate(dx, fields_);
}
private:
constexpr ValueType calculate(ValueType dx, const SomeStruct<FieldType>& someStruct) {
ValueType result = 0;
for (size_t i = 0; i < n_; ++i) {
auto dy = func_(someStruct.a_ + i * dx);
auto area = dy * dx;
result += area;
}
return result;
}
};
template<typename FieldType, typename ValueType, typename Func>
SomeClass(SomeStruct<FieldType>, ValueType, Func) ->
SomeClass<FieldType, ValueType, Func>;

我现在尝试这样使用该类：

template<typename T>
constexpr T funcA(T x) {
return x;
}
template<typename T>
constexpr T funcB(T x) {
return x*x;
}
int main() {
SomeClass a{SomeStruct{1.0, 3.0}, 1000, &funcA<double>};
// a.evaluate();
SomeClass b{SomeStruct{3.5, 7.5}, 2000, &funcB<double>};
// b.evaluate();
return 0;
}

我收到这个视觉工作室错误...

1>------ Build started: Project: Computations, Configuration: Debug Win32 ------
1>main.cpp
1>c:users...main.cpp(33): error C2440: 'initializing': cannot convert from 'initializer list' to 'Integrator<double,int,T (__cdecl *)(T)>'
1>        with
1>        [
1>            T=double
1>        ]
1>c:users...main.cpp(33): note: No constructor could take the source type, or constructor overload resolution was ambiguous
1>Done building project "Computations.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

这是在我调用其公共evaluate()函数之前生成的，该函数将调用其 私人calculate()功能...

我正在尝试解决此编译器错误，并且我正在尝试确保我能够正确调用存储在此类中的函数对象、函数指针、函子、lambda......