Const
What a class vector of a value stems from, which decides the dispatch that can use it.
the class attribute, set by structure(..., class = ) or class<-, S3 dispatches on it
structure(..., class = )
class<-
a value without a class attribute, R dispatches on its implicit class (double, numeric, ...)
double
numeric
an instance of the S4 class new creates
new
What a class vector of a value stems from, which decides the dispatch that can use it.