Template instantiation declaration syntax
>>-extern--template--template_declaration----------------------><
The act of creating a new definition of a function, class, or member of a class from a template declaration and one or more template arguments is called template instantiation. The definition created from a template instantiation to handle a specific set of template arguments is called a specialization.
A forward declaration of a template instantiation has the form of an explicit template instantiation preceded by the extern keyword.
The language feature is an orthogonal extension to Standard C++ for compatibility with GNU C++, and is described further in Explicit instantiation (C++ only).
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