InternalMethods Internal Generic FunctionsMany R-internal functions are generic and allow methods to be written for.
The following primitive and internal functions are generic, i.e., you can write methods for them:
length, length<-, lengths, dimnames, dimnames<-, dim, dim<-, names, names<-, levels<-, @<-,
as.character, as.complex, as.double, as.integer, as.logical, as.raw, as.vector, as.call, as.environment is.array, is.matrix, is.na, anyNA, is.nan, is.finite is.infinite is.numeric, nchar rep, rep.int rep_len seq.int (which dispatches methods for "seq"), is.unsorted and xtfrm
In addition, is.name is a synonym for is.symbol and dispatches methods for the latter. Similarly, as.numeric is a synonym for as.double and dispatches methods for the latter, i.e., S3 methods are for as.double, whereas S4 methods are to be written for as.numeric.
Note that all of the group generic functions are also internal/primitive and allow methods to be written for them.
.S3PrimitiveGenerics is a character vector listing the primitives which are internal generic and not group generic. Currently as.vector, cbind, rbind and unlist are the internal non-primitive functions which are internally generic.
For efficiency, internal dispatch only occurs on objects, that is those for which is.object returns true.
methods for the methods which are available.
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