How to Declare Non-Integral Static Data Members in C Class Templates?

Declaring Static Data Members in Class Templates

In object-oriented programming, it is often necessary to declare static data members within class templates. This can be challenging due to the inherent non-integral nature of such data members. One approach to overcome this limitation is to separate the declaration and definition statements.

Consider the following example code:

template <typename T>
struct S
{
    ...
    static double something_relevant; // Declaration
};

This declaration creates a static data member named "something_relevant" within the class template "S". However, since it is not of integral type, the compiler will not accept this declaration.

To resolve this issue, the definition of "something_relevant" can be placed in a separate statement:

template <typename T>
double S<T>::something_relevant = 1.5; // Definition

By defining the static data member outside the class declaration, the compiler can ensure that the definition is only evaluated once, regardless of how many instances of the class template are created.

This technique allows for the creation of static data members within class templates, even if they are not of integral type. It also ensures that the static data member is initialized with the correct value.

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