Partial template specialization
Encyclopedia
Partial template specialization is a particular form of class template specialization. Usually used in reference to the C++
programming language
, it allows the programmer to specialize only some arguments of a class template, as opposed to explicit specialization, where all the template arguments are provided.
If one knows that a class template will be used with a specific data type fairly often and this data type allows some optimizations (e.g. bit shifting with integers, as opposed to multiplying or dividing by 2), one may specialize the template by specifying another class template that is identical but by specifying the parameter types. When the compiler sees such a class template instantiated in code, it will generally choose the most specialized template definition that matches the instantiation. Therefore, an explicit specialization (one where all the template arguments are specified) will be preferred to a partial specialization if all the template arguments match.
At least the GNU, Intel, Comeau, and Microsoft compilers fully support partial specialization of templates.
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
, it allows the programmer to specialize only some arguments of a class template, as opposed to explicit specialization, where all the template arguments are provided.
Templates and specialization
Class templates are really meta-classes: they are partial abstract data types that provide instructions to the compiler on how to create classes with the proper data members. For example, the C++ standard containers are class templates. When a programmer uses a vector, one instantiates it with a specific data type, for example, int, string or double. Each type of vector results in a different class in the compiler's object code, each one working with a different data type.If one knows that a class template will be used with a specific data type fairly often and this data type allows some optimizations (e.g. bit shifting with integers, as opposed to multiplying or dividing by 2), one may specialize the template by specifying another class template that is identical but by specifying the parameter types. When the compiler sees such a class template instantiated in code, it will generally choose the most specialized template definition that matches the instantiation. Therefore, an explicit specialization (one where all the template arguments are specified) will be preferred to a partial specialization if all the template arguments match.
Partial specialization
Templates can have more than one parameter type. Some older compilers allow one only to specialize either all or none of the template's parameters. Compilers that support partial specialization allow the programmer to specialize some parameters while leaving the others generic. Until recently most compilers did not support this feature well (at best) or ignored such specializations (at worst).At least the GNU, Intel, Comeau, and Microsoft compilers fully support partial specialization of templates.