When it comes to C++ programming, templates are a powerful tool that can help you write more efficient and flexible code. One of the most important aspects of templates is the argument list, which specifies the types and values that will be used to instantiate the template. In this article, we’ll take a closer look at the argument list for class templates and explore some of the key concepts you need to know.
Before we dive into the details, let’s start with a quick overview of what class templates are and how they work. Essentially, a class template is a blueprint for creating a family of related classes. The template itself is not a class, but rather a set of instructions for how to create classes based on a specific pattern. When you create an instance of a class template, you provide a set of arguments that are used to fill in the template and create a new, unique class.
Now that we have a basic understanding of class templates, let’s take a closer look at the argument list. The argument list is a set of one or more template parameters that are used to define the template. These parameters can be either type parameters or non-type parameters, depending on the needs of your program.
Template Parameters
There are two main types of template parameters: type parameters and non-type parameters. Type parameters are used to specify the types of objects that will be used in the template, while non-type parameters are used to specify values that will be used in the template. Let’s take a closer look at each of these parameter types.
Type Parameters
Type parameters are used to specify the types of objects that will be used in the template. For example, you might use a type parameter to specify the type of a container that will be used to store data. Type parameters are specified using the typename keyword, followed by the name of the parameter. For example:
template <typename T>
class MyContainer {
public:
void add(T element);
T get(int index);
private:
T elements[100];
int size;
};
In this example, the template parameter T is used to specify the type of the elements array. When you create an instance of the MyContainer class, you provide a type argument that specifies the type of the elements array. For example:
MyContainer<int> myInts;
MyContainer<std::string> myStrings;
Non-Type Parameters
Non-type parameters are used to specify values that will be used in the template. For example, you might use a non-type parameter to specify the size of a container that will be used to store data. Non-type parameters are specified using the typename keyword, followed by the name of the parameter and its initial value. For example:
template <typename T, int size>
class MyContainer {
public:
void add(T element);
T get(int index);
private:
T elements[size];
int size;
};
In this example, the template parameter size is used to specify the size of the elements array. When you create an instance of the MyContainer class, you provide a value for the size argument that specifies the size of the elements array. For example:
MyContainer<int, 10> myInts;
MyContainer<std::string, 20> myStrings;
Template Specialization
Another important concept to understand when working with class templates is template specialization. Template specialization allows you to provide a different implementation of a template for a specific set of arguments. For example, you might want to provide a different implementation of a container class for a specific type of data. To do this, you can create a specialized version of the template that provides a different implementation for the specific type. Here’s an example:
template <typename T>
class MyContainer {
public:
void add(T element);
T get(int index);
private:
T elements[100];
int size;
};
template <>
class MyContainer<char*> {
public:
void add(char* element);
char* get(int index);
private:
char* elements[100];
int size;
};
In this example, we’ve created a specialized version of the MyContainer template for the char* type. This specialized version provides a different implementation of the
