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A general description is here.
‘formula’ objects are slightly more “first class”: e.g., ‘formula()’ or ‘new("formula", y ~ x)’ are now valid. Similarly, for ‘"table"’, ‘"ordered"’ and ‘"summary.table"’. Packages defining S4 classes with the above S3/S4 classes as slots should be reinstalled.
‘diag()’ no longer duplicates a matrix when extracting its diagonal.
The ‘quietly’ argument of ‘library()’ is correctly propagated from ‘.getRequiredPackages2()’ now.