This blog is updated daily.
A general description is here.
HTML help is now generated dynamically using an HTTP server running in the R process and listening on the loopback interface.
- Those who need to worry about security implications of such a server can disable it by setting the environment variable R_DISABLE_HTTPD to a non-empty value. This disables help.start() and HTML help (so text help is shown instead).
- The Java/Javascript search engine has been replaced by an HTML interface to help.search(). help.start() no longer has an argument 'searchEngine' as it is no longer needed.
- The HTML help can now locate cross-references of the form \link[pkg]{foo} and \link[pkg:foo]{bar} where 'foo' is an alias in the package, rather than the documented (basename of a) filename (since the documneentation has been much ignored).
- Details may change before release.
list.files() (also known as dir()) has a new argument 'include.dirs' to control whether directories are included in the listing: the default of include.dirs = !recursive is unchanged.
A different regular expression engine is used for basic and extended regexps and is also for approximate matching. This is based on the TRE library of Ville Laurikari, a modifed copy of which is included in the R sources.
This is often faster, especially in a MBCS locale.
Some known differences are that it is less tolerant of invalid inputs in MBCS locales, and in its interpretation of undefined (extended) regexps such as "^*". Also, the interpretation of ranges such as [W-z] in caseless matching is no longer to map the range to lower case.
This engine may in future be used in 'literal' mode for fixed = TRUE, and there is a compile-time option in src/main/grep.c to do so.
Basic and extendedExtended (and basic) regexps now support same set of options as for fixed = TRUE and perl = TRUE, including 'useBytes' and support for UTF-8-encoded strings in non-UTF-8 locales.
The algorithm used by strsplit() has been reordered to batch by elements of 'split': this can be much faster for fixed = FALSE (as multiple compilation of regexps is avoided).
New functions memCompress() and memDecopmmpress() for in-memory compression and decompression.
gzfile() looks at the file header and so can now also read bzip2-ed files and xv-comppressed files (where supported).
The check for consistent ordering of superclasses was not ignoring all conditional relations (the symptom was usually spurious warnings for classes extending "array").
CHM help is no longer made by default, and support for it may
be withdrawn entirely before release.
CHM help is no longer supported.
The help default has been changed to be HTML help rather than CHM help (which is currently unavailable). [Not yet the MSI installer.]
Binary packages are installed without CHM help if they contain it.