What is the usage of C++ templates?

C++ templates are a tool for creating generic code that allows writing algorithms or data structures that can operate on different data types without specifying a specific one.

There are two main types of C++ templates: function templates and class templates.

Function templates allow for the definition of a generic function that can operate on different data types. The syntax for function templates is as follows:

template <typename T>
T max(T a, T b) {
   return (a > b) ? a : b;
}

In the example above, the typename T represents a type parameter, which can be any type. The max function can compare different types of parameters and return the greater value.

Template classes allow the definition of a generic class that can operate on different data types. The syntax for template classes is as follows:

template <typename T>
class Stack {
   private:
      T data[100];
      int top;
   public:
      // 构造函数、成员函数等
};

In the example above, typename T represents a type parameter, so the Stack class can be instantiated with different data types. For instance, Stack is a stack that only stores integers, while Stack is a stack that only stores double-precision floating point numbers.

When using templates, specific data types can be provided as needed. For example, you can use max(a, b) to call the max function and specify the parameter type as an integer.

Templates are powerful and flexible features in C++, they can enhance code reusability and generality. However, when using templates, one should be mindful of concepts such as type inference and template specialization to avoid compilation errors or unexpected behavior.