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 c++ template specialization 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 kanye gifs apply to the argument-list of a partial template specialization:. Partial template specializations are not found by name lookup, 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. Specialization must be declared before the first use that would cause implicit instantiation, in every translation unit where such use occurs:. A template specialization that was declared but not defined can be used just like any other incomplete type e. When specializing a function template, its template arguments can be omitted if template argument deduction can provide them from the function arguments:.

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. It's worth pointing out that the salient reason for the specialization in this case was to allow for a more space-efficient implementation, but you could think of other reasons why this might come in handy--for instance, if you wanted to add extra methods to one templated class based on its type, but not to other templates. 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.

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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.

We write code once and use it for any data type including user defined data types. For example, sort can be written and used to sort any data type items. A class stack can be created that can be used as a stack of any data type. What if we want a different code for a particular data type? Consider a big project that needs a function sort for arrays of many different data types. Let Quick Sort be used for all datatypes except char. In case of char, total possible values are and counting sort may be a better option.

C++ template specialization

Templates are parameterized by one or more template parameters , of three kinds: type template parameters, non-type template parameters, and template template parameters. When a class template specialization is referenced in context that requires a complete object type, or when a function template specialization is referenced in context that requires a function definition to exist, the template is instantiated the code for it is actually compiled , unless the template was already explicitly specialized or explicitly instantiated. Instantiation of a class template does not instantiate any of its member functions unless they are also used. At link time, identical instantiations generated by different translation units are merged. The definition of a class template must be visible at the point of implicit instantiation, which is why template libraries typically provide all template definitions in the headers e. Files that instantiated exported templates did not need to include their definitions: the declaration was sufficient. Implementations of export were rare and disagreed with each other on details. A simple-template-id that names a class template specialization names a class. A template-id that names an alias template specialization names a type.

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Just like with members of primary templates, they only need to be defined if used in the program. Declarations Overview Declaration syntax decl-specifier-seq Declarator Conflicting declarations Specifiers typedef. Conflicting declarations. Copy assignment. The general rule of thumb is that the compiler will pick the most specific template specialization--the most specific template specialization is the one whose template arguments would be accepted by the other template declarations, but which would not accept all possible arguments that other templates with the same name would accept. Skip to content. A template has multiple types and only some of them need to be specialized. Share your thoughts in the comments. Alternative representations. Virtual function. Using function templates we can reduces the size of the code and makes the maintenance code easy. CWG Similar Reads. The following restrictions apply to the argument-list of a partial template specialization:.

And finally, it shows how concepts can be used to do it all in a much cleaner and more readable fashion. This section is a quick introduction for people who are new to templates or who haven't programmed their own templates before. Feel free to skip it if this is old news to you.

Views View Edit History. Get paid for your published articles and stand a chance to win tablet, smartwatch and exclusive GfG goodies! Template specialization. But when the user feeds characters into the parameter, the meaning is not obvious. Provide product feedback. How does template specialization work? Partial specialization allows template code to be partially customized for specific types in situations, such as:. Value categories. Default-initialization Value-initialization Zero-initialization Copy-initialization Direct-initialization. Function declaration.