nil

From: Tomasz Kowalczyk (tomek_at_[hidden])
Date: 2000-05-28 02:09:16

Hello everybody,

I would like to ask to add a nil structure to utility.hpp. It is useful
for specifying empty arguments in template specializations. For example:

template <class T1 = nil>
struct F {
        void f(T1);
};

template <>
struct F<> {
        void f();
};

The definition would most like look like:

namespace boost {
        struct nil {};
}

Lambda library and Peter Dimov's expression library use this technique
extensively, and I have found myself using it a lot too. Why not to
place a structure like this in a common, well known place, so that
people using or contributing to boost do not have to invent the same
thing with a different name again and again ?

Tomasz