- PLT now supports multi-core parallelism via futures. Futures create tasks that run in parallel, as long as the tasks stay in the "fast path" of the runtime system. For more information, see the guide.
- Our unit testing framework, schemeunit, is now included in the distribution. A graphical test runner is available via schemeunit/gui.
- The support languages for the "Programming Languages: Application and Interpretation" textbook by Shriram Krishnamurthi are now part of PLT Scheme. In addition the PLAI GC language comes with a random mutator generator (to help test collectors) and an improved heap visualizer.
- New Russian and Ukranian translations, thanks to Sergey Semerikov.
- A number of improvements to Redex's typesetting facilities.
- Typed Scheme users can now automatically generate predicates from types with define-predicate. Typed code can be inserted in untyped modules by requiring with-type from typed/scheme.
- The scheme/class library now provides contract combinators for classes (class/c) and objects (object/c). See the Reference and Guide for details. Also, a backwards-compatible object-contract version of object/c has replaced the old object-contract combinator.
- Writing new kinds of contracts is now easier with keyword-based constructors (make-contract and make-flat-contract), a simpler set of structure properties (prop:contract and prop:flat-contract), and the introduction of blame objects for tracking contract metadata.
- The Scheme-implemented bytecode reader fails less often. This is used by "mzc --decompile". The Scheme-implemented bytecode writer uses the compact bytecode format and fails less often. This may be used in the future for Scheme-implement bytecode processors.
- The language dialog now suggests using "#lang" more strongly as the default language. DrScheme no longer uses the term `Module language'.
Posted by Eli Barzilay at 21:51
PLT Scheme version 4.2.5 is now available from