C++ template specialization

Explicit specialization may be declared c++ template specialization 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. Specialization must be declared before the first use that would cause implicit instantiation, in every translation unit where such use occurs:, c++ template specialization. A template specialization that was declared but not defined can be used just like any other incomplete type e.

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.

C++ template specialization

Partial 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. Partial specialization has to appear after the non-specialized template declaration. The following restrictions apply to the argument-list of a partial template specialization:. Partial template specializations are not found by name lookup. Only if the primary template is found by name lookup, its partial specializations are considered. In particular, a using declaration that makes a primary template visible, makes partial specializations visible as well:. Informally "A is more specialized than B" means "A accepts a subset of the types that B accepts". Formally, to establish more-specialized-than relationship between partial specializations, each is first converted to a fictitious function template as follows:. The function templates are then ranked as if for function template overloading. The template parameter list and the template argument list of a member of a partial specialization must match the parameter list and the argument list of the partial specialization. Just like with members of primary templates, they only need to be defined if used in the program. Explicit full specialization of a member of a partial specialization is declared the same way as an explicit specialization of the primary template. If a primary template is a member of another class template, its partial specializations are members of the enclosing class template. If the enclosing template is instantiated, the declaration of each member partial specialization is instantiated as well the same way declarations, but not definitions, of all other members of a template are instantiated.

Member access operators.

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.

Partial 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. Partial specialization has to appear after the non-specialized template declaration. The following restrictions apply to the argument-list of a partial template specialization:. Partial template specializations are not found by name lookup. Only if the primary template is found by name lookup, its partial specializations are considered. In particular, a using declaration that makes a primary template visible, makes partial specializations visible as well:. Informally "A is more specialized than B" means "A accepts a subset of the types that B accepts". Formally, to establish more-specialized-than relationship between partial specializations, each is first converted to a fictitious function template as follows:.

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.

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CWG Open In App. Fundamental types Enumeration types Function types. Access specifiers. Save Article. Report issue Report. Operator overloading. Skip to main content. Parameters and arguments. Order of evaluation. For instance, you might have a vector of doubles with a method that returns the non-integer component of each element although you might think prefer inheritance in this case.

Every template is parameterized by one or more template parameters, indicated in the parameter-list of the template declaration syntax:. A structural type is one of the following types optionally cv-qualified, the qualifiers are ignored :.

Generic programming is an approach where generic data types are used as parameters in algorithms so that they work for variety of suitable data types. Default-initialization Value-initialization Zero-initialization Copy-initialization Direct-initialization. This time, however, instead of implementing a class for one specific type, you end up implementing a template that still allows some parameterization. So you might have two separate vector classes. The specialization itself is still a template on the type pointed to or referenced. Fundamental types. Engineering Exam Experiences. Function template. Usual arithmetic conversions. Linkage specification. Just like with members of primary templates, they only need to be defined if used in the program. Aggregate initialization. When we designed the function add T x, T y , the meaning was clear: add the two numbers. Using function templates we can reduces the size of the code and makes the maintenance code easy.