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C++ non-type template parameters of the basic concept, many novices are not very clear, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can get something.

The C++ programming language has attracted the attention of developers immediately after its advent. It has the functions of the C language and can support many programming styles. What we are going to introduce to you today is some basic concepts of C++ non-type class template parameters, so that you can have a more in-depth understanding of this aspect.

I think the C++ untyped class template parameter is equivalent to the role of a global constant. The following examples are given to illustrate non-type class templates. By redefining a Stack template, this chapter requires that a fixed-size array be used as the container for the element, and that the size of the array can be defined by the user of the template. Then, for the template designer, an interface should be provided so that the user can define the size of the array. This requires the use of non-type class template parameters. The following code explains the problem very well:

# include

< iostream>

# include

< string>

# include

< cstdlib>

# include

< stdexcept>

Template

< typename T, int MAXSIZE>

Class Stack {private: t elems [MAXSIZE]; int numElems; public: Stack (); void push (T const&); void pop (); T top () const; bool isEmpty () const {return numElems = = 0;} bool isFull () const {return numElems = = MAXSIZE;}}; template

< typename T, int MAXSIZE>

Stack

< T, MAXSIZE>

:: Stack (): numElems (0) {/ / do nothing but initialize numElems. } template

< typename T, int MAXSIZE>

Void Stack

< T, MAXSIZE>

:: push (T const& elem) {if (numElems = = MAXSIZE) {throw std::out_of_range ("Stack

< >

:: push () = > stack is full. ");} elems [numElems] = elem; + + numElems;} template

< typename T, int MAXSIZE>

Void Stack

< T, MAXSIZE>

:: pop () {47 if (numElems

< = 0) { throw std::out_of_range("Stack< >

:: pop: empty stack ");}-- numElems;} template

< typename T, int MAXSIZE>

T Stack

< T, MAXSIZE>

:: top () const {if (numElems) {throw std::out_of_range ("Stack

< >

:: pop: empty stack ");} / / returns an element. Return elems [numElems-1];} int main () {try {Stack

< int, 20>

Int20Stack; Stack

< int, 40>

Int40Stack; Stack

< std::string, 40>

StringStack; int20Stack.push (7); std::cout < < "int20Stack.top ():" < < int20Stack.top () < < std::endl; int20Stack.pop (); stringStack.push ("HelloWorld!"); std::cout < < "stringStack.top ():" < < stringStack.top () < < std::endl; stringStack.pop (); stringStack.pop () } catch (std::exception const& ex) {std::cerr < < "Exception:" < < ex.what () < < std::endl; return EXIT_FAILURE;} return 0;}

The above code reveals the definition and use of C++ untyped class template parameters.

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