The GClosure structure
GClosure is a transparent-type that represents an R function.
When an API function requests a
GClosure as a parameter, the user may pass any R function OR
an R object of class
GClosure that is returned by certain API functions.
GClosure represents an external object and thus inherits from
GClosure objects may be coerced by the function
to an R closure. This means that you can effectively invoke external closures
(which may be implemented in C or R) in the same way as R functions.
an R closure with an extra
refattribute holding the original external reference