Saturday, January 18, 2014

specialization of class template c++

Specializations of Class Templates : templates tutorial
You can specialize a class template for certain template arguments. Similar to the overloading of function templates, specializing class templates allows you to optimize implementations for certain types or to fix a misbehavior of certain types for an instantiation of the class template. However, if you specialize a class template, you must also specialize all member functions. Although it is possible to specialize a single member function, once you have done so, you can no longer specialize the whole class.
To specialize a class template, you have to declare the class with a leading template<> and a specification of the types for which the class template is specialized. The types are used as a template argument and must be specified directly following the name of the class:

For these specializations, any definition of a member function must be defined as an "ordinary" member function, with each occurrence of T being replaced by the specialized type:

Here is a complete example of a specialization of Stack<> for type std::string:

In this example, a deque instead of a vector is used to manage the elements inside the stack. Although this has no particular benefit here, it does demonstrate that the implementation of a specialization might look very different from the implementation of the primary template.
In fact, there is a benefit for using a deque instead of a vector to implement a stack: A deque frees memory when elements are removed, and it can't happen that elements have to be moved as a result of reallocation. However, this is no particular benefit for strings. For this reason it is probably a good idea to use a deque in the primary class template (as is the case in class std::stack<> of the C++ standard library).

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