Re: [Boost-users] [variant][any] template parameterized variant

On 08/10/2010 20:42, alfC wrote:

Hi,

I need a variant type object that can hold any type characterized by a template. For example Boost.Units have a family of types parameterized by "System".

quantity< unit, double>

suppose dimension is fixed, e.g. typedef boost::units::length dimension

is it possible to define a variant over that family of types?

No.

I could create a make_variant_over< list of all types> but that can be that list will be fixed and each time I defined a new System the list will have to grow.

Variant can only work with a fixed list of possible types.

Or should I be using an extension of boost::any with some adhoc restriction over the possible types on construction?

You could use type erasure.