[英]CPP templated member function specialization
I'm trying to specialize the member function moment() only (not the hole class) like this: 我正在尝试专门化成员函数moment()(不是孔类),如下所示:
template<class Derived, class T>
class AbstractWavelet {
public:
[...]
template<bool useCache>
const typename T::scalar moment(const int i, const int j) const {
return abstractWaveletSpecialization<Derived, T, useCache>::moment(static_cast<const Derived*>(this), i, j);
}
template<bool useCache>
friend const typename T::scalar abstractWaveletSpecialization<Derived, T, useCache>::moment(const Derived* const that, const int i, const int j);
protected:
// returns the jth moment of the ith scaling function
template<bool useCache>
inline const typename T::scalar momentImpl(const int j, const int i) const {
[...]
} // momentImpl
};
The actual specialization happens in an extra abstractWaveletSpecialization struct: 实际的特化在一个额外的abstractWaveletSpecialization结构中发生:
template<class Derived, class T, bool useCache>
struct abstractWaveletSpecialization {
inline static const typename T::scalar moment(const Derived* const that, const int i, const int j) {
return that->momentImpl<useCache>(i,j);
}
};
template<class Derived, class T>
struct abstractWaveletSpecialization<Derived, T, true> {
typedef const std::pair<const int, const int> momentCacheKey;
typedef std::map<momentCacheKey,
const typename T::scalar> momentCacheType;
static momentCacheType momentCache;
inline static const typename T::scalar moment(const Derived* const that, const int i, const int j) {
momentCacheKey cacheKey(i,j);
typename momentCacheType::iterator idx = momentCache.find(cacheKey);
if (idx == momentCache.end())
return that->momentImpl<true>(i, j); // COMPILE ERROR HERE
else
return momentCache[cacheKey];
}
};
The problem is that I cannot call momentImpl() in the specialized abstractWaveletSpecialization struct: 问题是我不能在专门的abstractWaveletSpecialization结构中调用momentImpl():
error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘bool’ to binary ‘operator<’
But the compiler does not complain about the call of momentImpl in the non-specialized abstractWaveletSpecialization struct. 但是编译器并没有抱怨在非专用的abstractWaveletSpecialization结构中调用momentImpl。
Is my approach forbidden in C++? 我的方法是否在C ++中被禁止? Or is there any way to make this work?
或者有什么方法可以使这项工作?
Can you try that->template momentImpl<true>(i, j);
你能试试吗
that->template momentImpl<true>(i, j);
please ? 请 ? It's a way to tell the compiler "Hey, the thing after -> is a templated call"
这是一种告诉编译器的方法“嘿,事后 - >是一个模板化的调用”
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