From: Eli Barzilay <eli@barzilay.org>
To: plt-announce@list.cs.brown.edu
Subject: [PLT announcement] PLT Scheme v4.2.4
Date: Thu, 28 Jan 2010 21:32:33 -0500

PLT Scheme version 4.2.4 is now available from

  http://plt-scheme.org/

* The `scheme/flonum’ and `scheme/fixnum’ libraries provide flonum-
  and fixnum-specific operations.  In the case of flonum-specific
  operations, the JIT compiler can recognize combinations of
  operations (including local bindings) and improve performance by
  "unboxing" intermediate results.

* The `scheme/unsafe/ops’ library provides arithmetic and other
  operations that are implemented without dynamic checks.  Avoiding
  checks can sometimes improve performance, but at the expense of
  safety.

* `2htdp/universe’: We have severed the connection between universe
  and an image library and made a few other, minor changes.  Most
  programs will now have to change to require the `htdp/image’
  library explicitly.  For the full details, see the new Porting
  World Programs section of the documentation:
    http://docs.plt-scheme.org/teachpack/2htdphtdp-port.html

* The `2htdp/image’ library continues to grow.  In this release, it
  is supported by `2htdp/universe’, equality changed to be based on
  how the images are drawn, cropping and curves were added, and
  support for more kinds of pens were added.

* `htdp/world’: The old world teachpack remains deprecated.  HtDP/2e
  exclusively uses the new 2htdp/universe library.  For backwards
  compatibility, the world teachpack will remain in the distribution
  until the coming summer.

* The `scheme/class’ library now provides `this%’, which refers to
  the class of the current object (i.e. `this’).

* `scheme/generator’ has convenient functions for infinite
  generators, and for converting a generator to a sequence for
  iteration.

* PLT Scheme’s add-on directory can be customized by the
  $PLTADDONDIR environment variable or `--addon’/`-A’ command-line
  flags.  This controls where downloaded Planet packages and their
  compiled Scribble documentation are installed.

* Additional extensions include: saving `errno’ in foreign calls,
  much improved `sort’ speed, normalized results from
  `procedure-arity’, and more.

[Note that mirror sites can take a while to catch up with the new
downloads.]

Feedback Welcome,
-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!