Give the Rd tags at the top level of an Rd object.

## Usage

Rdo_tags(rdo, nulltag = "")

## Arguments

rdo

an Rd object.

nulltag

a value to use when Rd_tag is missing or NULL.

## Details

The "Rd_tag" attributes of the top level elements of rdo are collected in a character vector. Argument nulltag is used for elements without that attribute. This guarantees that the result is a character vector.

Rdo_tags is similar to the internal function tools:::RdTags. Note that tools:::RdTags may return a list in the rare cases when attribute Rd_tags is not present in all elements of rdo.

## Value

a character vector

## Author

Georgi N. Boshnakov

Rdo_which, Rdo_which_tag_eq, Rdo_which_tag_in
##---- Should be DIRECTLY executable !! ----