What is the difference between full and partial template specialization?

Full template specialization and partial template specialization are two ways to create specialized versions of a template, but they differ in how they specify the template arguments.

Full Specialization:

• Full specialization specifies values for all template parameters.
• It creates a completely new implementation for a specific set of template arguments.
• The template parameter list in the specialization is empty <>.

1template <typename T>
2class MyClass {/* ... */ };
3
4// Full specialization for T = int
5template <>
6class MyClass<int> {/* ... */ };

Partial Specialization:

• Partial specialization specifies values for only a subset of template parameters.
• It creates a new implementation for a specific pattern of template arguments.
• The template parameter list in the specialization contains the remaining unspecified parameters.

1template <typename T, typename U>
2class MyClass {/* ... */ };
3
4// Partial specialization for U = int
5template <typename T>
6class MyClass<T, int> {/* ... */ };

Use full specialization when you need to provide a completely different implementation for a specific type or set of types. Use partial specialization when you want to specialize a template based on a pattern of template arguments while still allowing some arguments to vary.

Partial specialization is particularly useful when you have multiple template parameters and want to specialize based on a subset of them. It allows you to create more targeted specializations without having to specify all the arguments.