Racket v5.1.2
* The download page includes 64-bit installers for Mac OS X,
Windows, and two Debian flavors. Racket now supports OS X Lion.
* Racket now includes a new `racket/place' library to support
parallelism, complementing `racket/future'. Racket's parallel
build process is now based on places instead of multiple OS
processes.
Places support share-nothing parallelism and message-passing
communication. Compared to futures, places are heavyweight, but
they have a simpler performance model.
* The syntax-certificate system has been replaced by a syntax-taint
system. Both certificates and taints were designed to protect
otherwise inaccessible bindings from abuse when they appear in
macro expansions. Taints are simpler and lighter, and the switch
closes known holes in the certificate system. Macros that are not
implemented with `syntax-rules' or `define-syntax-rule', however,
must explicitly use `syntax-protect' to protect their expansions
from abuse.
* The `net/url' library supports HTTPS connections, but beware that
by default all sites are accepted (equivalent to ignoring a
browser's warnings about untrusted certificates).
* Error messages in the student languages use a simplified
vocabulary and consistent phrasings. If you maintain curriculum
material or teachpacks then please consider updating. See the
"Error Message Composition Guidelines" section in the
documentation for details.
* Typed Racket: almost all core Racket data structures and
operations are now accessible in Typed Racket (most of this work
is due to prolific contributor Eric Dobson). The performance of
the typechecker has been significantly improved.
* The `scriblib/bibtex' library supports BibTeX-formatted citation
databases in Scribble documents. BibTeX can be tricky to parse,
so please report failed entries as bug reports.
* The `for' forms now support an `#:unless' clause, and a
nonnegative integer can be used as a sequence. The new `compose1'
function creates single-valued composition functions. The
`racket/function' library now provides `identity', `thunk', and
`thunk*'.
* The license has been clarified: we now use LGPLv2.1 uniformly.
(The license file used to specify LGPLv2, contrary to the download
pages.)
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