[Boost-users] Runtime identity

I'm not sure if this is a stupid question, but is there a runtime equivalent of boost.mpl's identity metafunction? Something that just returns it's single argument, eg., template <typename T> T identity( T t ) { return t; } I think it's trivially simple to write, but I wonder if it already exists in Boost or indeed the STL? (I need this because I need to pass a function object which simply returns an object I already have - maybe I've missed a more obvious method?) Thx, Rob.