1.8 KiB
1.8 KiB
Partial specialization
Template function partial specialization
In C++ we cannot partially specialize functions.
Template class partial specialization
In C++ we can specialize classes partially. It means that we need to leave at least one template parameter.
// primary template
template <typename T1, typename T2, typename T3>
class A {};
// partial specialization with T1 = int
template <typename T2, typename T3>
class A<int, T2, T3> {};
// partial specialization with T1 = int and T2 = double
template <typename T3>
class A<int, double, T3> {};
// partial specialization with T1 = int and T3 = char
template <typename T2>
class A<int, T2, char> {};
// full specialization with T1 = T2 = double and T3 = int
template <>
class A<double, double, int> {};
Advanced partial specialization
template <typename T1, typename T2, typename I>
class A {}; // primary template
template<typename T, typename I>
class A<T, T*, I> {}; // #1: partial specialization where T2 is a pointer to T1
template<typename T, typename T2, typename I>
class A<T*, T2, I> {}; // #2: partial specialization where T1 is a pointer
template<typename T>
class A<int, T*, double> {}; // #3: partial specialization where T1 is int, I is double,
// and T2 is a pointer
template<typename X, typename T, typename I>
class A<X, T*, I> {}; // #4: partial specialization where T2 is a pointer
Exercise
Write a partial specialization of VectorMap for boolean keys. We can have only 2 values for boolean keys. There is no need to keep vectors inside.
Implement properly all currently available functions.