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.