Can String Literals Be Used as Non-Type Template Parameters in C ?

Class Templates with Non-Type String Literals

In C , you may encounter the need to declare class templates with non-type parameters, such as string literals. This query explores the feasibility of this approach and provides a solution.

Non-Type Template Parameter Rationale

You might wish to utilize string literals directly as non-type template parameters for convenience or readability purposes. However, this is not directly supported in C .

A Feasible Workaround

While passing a string literal directly is not possible, a workaround involves using a const char* non-type template parameter and passing it a const char[] variable with static linkage. This method is nearly equivalent to passing a string literal.

Example Implementation

The following code demonstrates this workaround:

#include <iostream>    

template<const char *str> 
struct cts {
    void p() {std::cout << str;}
};

static const char teststr[] = "Hello world!";
int main() {
    cts<teststr> o;
    o.p();
}

Explanation

• The class template cts is defined with a const char* non-type template parameter str.
• A statically linked const char[] variable named teststr is declared and initialized with the string literal "Hello world!".
• In the main function, an instance of cts is created using teststr as the template argument.
• The p() member function of the cts object prints the string stored in str.

Conclusion

This workaround allows you to effectively use string literals in class templates as non-type parameters. It provides an alternative solution when direct string literal input is not feasible.

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