C++ template specialization

Explicit specialization may be declared in any scope where its primary template may be defined which may be different from the scope where the primary template is defined; such as with out-of-class specialization of a member template. Explicit specialization has to appear after the non-specialized template declaration, c++ template specialization.

This tutorial will give the idea of the template specialization, but will be limited to just the basic. In other words, a template is a mechanism that allows a programmer to use types as parameters for a class or a function. The compiler then generates a specific class or function when we later provide specific types as arguments. In a sense, templates provide static compile-time polymorphism , as opposed to dynamic run-time polymorphism. However, sometimes a template cannot or should not be applied to a certain types of data.

C++ template specialization

Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Class templates can be partially specialized, and the resulting class is still a template. Partial specialization allows template code to be partially customized for specific types in situations, such as:. A template has multiple types and only some of them need to be specialized. The result is a template parameterized on the remaining types. A template has only one type, but a specialization is needed for pointer, reference, pointer to member, or function pointer types. The specialization itself is still a template on the type pointed to or referenced. The following code demonstrates a collection class template Bag and a partial specialization for pointer types in which the collection dereferences the pointer types before copying them to the array. The collection then stores the values that are pointed to. With the original template, only the pointers themselves would have been stored in the collection, leaving the data vulnerable to deletion or modification. In this special pointer version of the collection, code to check for a null pointer in the add method is added. The following example defines a template class that takes pairs of any two types and then defines a partial specialization of that template class specialized so that one of the types is int. The specialization defines an additional sort method that implements a simple bubble sort based on the integer. Coming soon: Throughout we will be phasing out GitHub Issues as the feedback mechanism for content and replacing it with a new feedback system. Skip to main content.

Reference initialization. Assignment operators. When the type of elements is char, we may want to use a simple boolean array of size to make a set.

How to begin Get the book. Practice problems Quizzes. Template Specialization and Partial Template Specialization By Alex Allain Template Specialization In many cases when working with templates, you'll write one generic version for all possible data types and leave it at that--every vector may be implemented in exactly the same way. The idea of template specialization is to override the default template implementation to handle a particular type in a different way. For instance, while most vectors might be implemented as arrays of the given type, you might decide to save some memory and implement vectors of bools as a vector of integers with each bit corresponding to one entry in the vector. So you might have two separate vector classes.

In the previous lesson As it turns out, it is not only possible to specialize functions, it is also possible to specialize classes! Consider the case where you want a class that stores 8 objects. Consequently, a variable of type bool ends up using an entire byte even though technically it only needs a single bit to store its true or false value! Thus, a bool is 1 bit of useful information and 7 bits of wasted space. While we could create an entirely new class to do so, this has one major downside: we have to give it a different name. Class template specialization allows us to specialize a template class for a particular data type or data types, if there are multiple template parameters. Class template specializations are treated as completely independent classes, even though they are allocated in the same way as the templated class. Just like all templates, the compiler must be able to see the full definition of a specialization to use it. Also, defining a class template specialization requires the non-specialized class to be defined first.

C++ template specialization

How to begin Get the book. Practice problems Quizzes. Template Specialization and Partial Template Specialization By Alex Allain Template Specialization In many cases when working with templates, you'll write one generic version for all possible data types and leave it at that--every vector may be implemented in exactly the same way. The idea of template specialization is to override the default template implementation to handle a particular type in a different way. For instance, while most vectors might be implemented as arrays of the given type, you might decide to save some memory and implement vectors of bools as a vector of integers with each bit corresponding to one entry in the vector. So you might have two separate vector classes. The first class would look like this. So we might make our boolean vector look a little bit different by representing the data as an array of integers whose bits we manually manipulate.

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Integer literals Floating-point literals Boolean literals Character literals. Class declaration. You will be notified via email once the article is available for improvement. Keywords Escape sequences. Using function templates we can reduces the size of the code and makes the maintenance code easy. However, sometimes a template cannot or should not be applied to a certain types of data. Formally, to establish more-specialized-than relationship between partial specializations, each is first converted to a fictitious function template as follows:. Partial specialization. Assignment operators Increment and decrement Arithmetic operators Logical operators Comparison operators Member access operators Other operators new -expression delete -expression throw -expression. If a partial specialization of the member template is explicitly specialized for a given implicit specialization of the enclosing class template, the primary member template and its other partial specializations are still considered for this specialization of the enclosing class template. You might wonder if you really want your sortedVector type to work like this--after all, if you're putting them in an array of pointers, you'd expect them to be sorted by pointer type. Other operators. Aggregate initialization.

And finally, it shows how concepts can be used to do it all in a much cleaner and more readable fashion.

Fundamental types Enumeration types Function types. Parameters and arguments. Create Improvement. A template has only one type, but a specialization is needed for pointer, reference, pointer to member, or function pointer types. Access specifiers friend specifier. That's OK for most things, but it would probably make more sense to have sorted on the actual object type instead of the pointer address. Access specifiers. Integer literals. This makes some sense if you think of it as a form of pattern matching where T matches the type if that type is followed by an asterisk. Logical operators. Add Other Experiences. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.