singleton objects in tag
hierarchies. Intended for framework authors.
surroundSingletons(ui)
takeSingletons(ui, singletons = character(0), desingleton = TRUE)takeSingletons).surroundSingletons preprocesses a tag object by changing any
singleton X into X'
where sig is the sha1 of X, and X' is X minus the singleton attribute.takeSingletons returns a list with the elements ui (the
processed tag objects with any duplicate singleton objects removed) and
singletons (the list of known singleton signatures).