Changes in Racket 5.2.1
* Performance improvements include the use of epoll()/kqueue()
instead of select() for the Racket thread scheduler, cross-module
inlining of small functions, and the use of SSE instead of x87 for
JIT-compiled floating-point operations on platforms where SSE is
always available (including x86_64 platforms). A related change
is the interning of literal numbers, strings, byte strings,
characters, and regexps that appear in code and syntax objects.
* DrRacket uses a set of composable ray-traced icons available from
the new `images' library collection.
* Typed Racket's `typecheck-fail' form allows macro creators to
customize the error messages that Typed Racket produces. This is
especially useful when creating pattern matching macros.
* The performance of Redex's matcher has been substantially
improved; depending on the model you should see improvements
between 2x and 50x in the time it takes to reduce terms.
* Plots look nicer and are more correct at very small and very large
scales. New features include customizable dual axis ticks and
transforms (e.g., log axes, date and currency ticks, axis interval
collapse and stretch), stacked histograms, and 3D vector fields.
The legacy `fit' function and libfit have been removed.
* The `2htdp/universe' library's `big-bang' form supports an
experimental game pad key handler.
* The `db' library now supports nested transactions and PostgreSQL
arrays. Bugs involving MySQL authentication and memory corruption
in the SQLite bindings have been fixed.
* The Macro Stepper tool in DrRacket no longer executes a program
after expanding it.
* In the DMdA teaching languages, infinite recursive signatures
("streams", for example) with no intervening `mixed' are now
supported, and the signatures of record definitions without fields
now have generators for use with `property'.
* MysterX's ActiveX support is deprecated and will be removed in the
next release. MysterX's core COM functionality will become
deprecated in the next release, but COM functionality will be
supported for the foreseeable future as a compatibility layer over
a forthcoming `ffi/com' library.
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