C++ template specialization

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.

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:. A function with the same name and the same argument list as a specialization is not a specialization see template overloading in function template.

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.

Class template. Operators Operator precedence.

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. In the example below, we have add function which takes two parameter and returns the same type of data after adding the two args. When we designed the function add T x, T y , the meaning was clear: add the two numbers.

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.

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.

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But there's a practical reason for doing this: when you allocate memory for an array of objects, the default constructor must be called to construct each object. In the example below, we have add function which takes two parameter and returns the same type of data after adding the two args. This tutorial will give the idea of the template specialization, but will be limited to just the basic. Thank you. Usual arithmetic conversions. A member or a member template may be nested within many enclosing class templates. Copy assignment. Implicit conversions - Explicit conversions. Just like with members of primary templates, they only need to be defined if used in the program. Namespaces Page Discussion.

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.

Contribute your expertise and make a difference in the GeeksforGeeks portal. Access specifiers friend specifier. Function templates allow the programmer to write a generic function which is independent of data type. Partial specialization has to appear after the non-specialized template declaration. Class member templates. Share your thoughts in the comments. If no default constructor exists for instance, if every object needs some data to be created , you're stuck needing a list of pointers to objects, but you probably want them to be sorted the same way the actual objects themselves would be! Declarations Overview Declaration syntax decl-specifier-seq Declarator Conflicting declarations Specifiers typedef. A member or a member template may be nested within many enclosing class templates. Increment and decrement. But a careful observation of overloaded functions as in our program will show us the disadvantage of overloaded function. Vote for difficulty :. String literals. Dependent names. CWG