arrays now behave consistently, notably for arrays of length zero.

Arithmetic between length-1 arrays and longer non-arrays had

silently dropped the array attributes and recycled.  This now

gives a warning and will signal an error in the future, as it has

always for logic and comparison operations in these cases (e.g.,

enabled by default at its level 3. This means functions will be

compiled on first or second use and top-level loops will be

compiled and then run.  (Thanks to Tomas Kalibera for extensive

For now, the compiler will not compile code containing explicit

: this is to support single stepping from

JIT compilation can be disabled for the rest of the session using

appropriate.  Additionally, for the case

Matrix products now consistently bypass BLAS when the inputs

inputs has been improved. Performance when BLAS is used is

improved for matrix/vector and vector/matrix multiplication (DGEMV

One can now choose from alternative matrix product implementations

implementation is not optimized for speed but consistent in

precision with other summations in R (using

for best speed, but usually with undefined behavior for inputs

more conveniently debugging S3 and S4 methods.  (Based on a patch by

be called by evaluating the given expression. When the call is to

method that would be dispatched. A number of internal utilities

were added to support this, most notably

a regular expression containing capture expressions,

now may remove extraneous white space and

hence somewhat more generous in displaying character vectors; this

(with which strict back compatibility is possible but not the

in the default case when eigenvectors are computed.

Zero-length date and date-time objects (of classes

(the default) which should behave the same as before when

in the result, and optionally parts of the internal

cross-validation errors for linear models.

After seven years of deprecation, duplicated factor levels

now produce a warning when printed and an error in

Invalid factors, e.g., with duplicated levels (invalid but

constructable) now give a warning when printed,