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A general description is here.
New generic function .DollarNames() to enable class authors
to customize completion after the $ extractor.
The 'open' modes for connections are now interpreted more consistently. open = "r" is now equivalent to open = "rt" for all connections. The default open = "" now means "rt" for all connections except the compressed file connections gzfile(), bzfile() and xzfile() for which it means "rb".
New Rd tag \ifelse to complement \if.
New generic function .DollarNames() to enable class authors to customize completion after the $ extractor.
load(), save(), dput() and dump() now open a not-yet-open connection in the appropriate mode (as other functions using connections directly already did).
Tags \if, \ifelse and \out have been added to allow format-specific (or more general, using \Sexpr) conditional text in man pages.