[plt-dev] Release Announcement for v4.2.4

The release announcement sketch that I have so far is below.  Please
mail me new items and/or edits, or changes to the order.  There is one
item (universe/world changes) that still needs to be written.  I've
shoved some of the smaller items (`sort', `procedure-arity', and
errno) into a catchall item.

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* 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.

* 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.

* Added a porting guide that explains how to turn `htdp/world'
  programs into `2htdp/universe' and `2htdp/image' programs.

* 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.



* [Matthias] `error' in teaching languages?  universe/world changes?
  `random', `gensym', `current-millisecond', `sleep', `assoc',
  `with-i/o-from-to' added?

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