How Can You Partially Specialize Class Member Functions in C ?

Partial Specialization of Class Member Functions in C

Partial specialization allows for the specialization of a specific instantiation of a templated class or function. This can be useful when different behavior is desired for different template argument values. However, a stumbling block often encountered by beginners is the partial specialization of class member functions.

To partially specialize a class member function, a non-member template function must be defined that takes the partially specialized class template as a parameter. For example, let's consider the following code:

template <typename T, int nValue>
class Object {
private:
    T m_t;
    Object(); // Private constructor

public:
    Object(T t): m_t(t) {}
    T Get() { return m_t; }
    Object& Deform() {
        m_t *= nValue;
        return *this;
    }
};

// Partial specialization of the Deform() method for nValue = 0
template <typename T>
Object<T, 0>& Object<T, 0>::Deform() {
    this->m_t = -1;
    return *this;
}

In this example, the Deform() member function is partially specialized for the case where nValue is 0. For all other values of nValue, the default behavior is applied. This allows for custom behavior when nValue is 0, while maintaining the generic implementation for other cases.

Note: It's important to note that you cannot partially specialize only a single member function. The entire class must be partially specialized in order to partially specialize a member function. This is reflected in the correct code below:

template <typename T>
class Object<T, 0> {
private:
    T m_t;
    Object(); // Private constructor

public:
    Object(T t): m_t(t) {}
    T Get() { return m_t; }
    Object& Deform() {
        std::cout << "Spec\n";
        m_t = -1;
        return *this;
    }
};

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