Template Parameters

Let's familiarize ourselves with template parameters in this lesson.

We'll cover the following

Alias Templates #

Alias templates aka template typedefs allow us to give a name to partially bound templates, which allows for partial specialization of templates.

template <typename T, int Line, int Col> class Matrix{
...
};
template <typename T, int Line>
using Square = Matrix<T, Line, Line>;
   template <typename T, int Line>
   using Vector = Matrix<T, Line, 1>;

Alias templates cannot be further specialized.

Template Parameters #

Every template is parameterized by one or more template parameters, indicated in the parameter-list of the template.

C++ supports three different kinds of template parameters

  1. Type parameters
std::vector<int> vec = {1, 2, 3, 4, 5};
  1. Non-type parameters
std::array<int, 5> arr = {1, 2, 3, 4, 5};
  1. Template-template parameters
template <typename T, template <typename, typename> class Cont> class Matrix{
...
Matrix<int, std::vector> myIntVec;

Types #

A type parameter is a typical case for template arguments.

  • Type parameters are class types and fundamental types

Non-Types #

Non-types are template parameters which can be evaluated at compile-time.

The following types are possible:

  • Integers and enumerations

  • Pointers to objects, functions, and attributes of a class

  • References to objects and functions

  • std::nullptr_t constant

With C++17, floating-point numbers and strings cannot be used as non-type parameters.

To learn more about template parameters, click here.

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