[plt-scheme] PLT Scheme v4.2.3

PLT Scheme version 4.2.3 is now available from

  http://plt-scheme.org/

* The unit test framework for the teaching languages provides
  `check-member-of' and `check-range' for checking "random
  functions", i.e., "functions" that may produce several different
  results for one and the same argument.

* Added a new image library, `2htdp/image'.  Significant changes
  from `htdp/image':
  - copying and pasting does not introduce jaggies
  - `equal?' comparisons are more efficient
  - added rotation & scaling
  - got rid of pinholes (new overlay, beside, above functions based
    on bounding boxes)

* The `scheme/vector' library provides common vector operations
  (also reprovided by `scheme').

* The `scheme/promise' library provides several new kinds of
  promises with alternatives execution strategies.

* New port-reading utilities: `in-port', `port->list', `file->list'.

* A new require-macro, `path-up', for requiring a file that is
  higher in the directory tree.

[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!