[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.  (This is close to the final version.)

The one item that is still missing, IMO, is:

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


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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.

* 2htdp/universe: We have severed the intimate connection between
  universe and the image library.  The most important change is that
  the design of world programs now demands the use of two
  teachpacks: 2htdp/universe and htdp/image (the old image library)
  or 2htdp/image (the new image library).  Furthermore, the
  callbacks for world programs no longer use symbols but strings.
  The image functions are overloaded so that both strings and
  symbols work as inputs.

  For upgrading your world programs, see the new Porting World Programs
  guide in the HtDP/2e section of the documentation.

* 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.

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