6.0 - Support for `define-type', `struct:', `make-predicate', etc. at the REPL - Performance work: optimized subtyping - Make `struct:' have the correct bindings in struct info - Use pairs for objects on arrow types - Split off `recover-source-syntax' into a separate package and generalized it - Lots of doc improvements - Lots of error message improvements - Split into multiple packages 5.3.4 - Moved Optimization Coach to the package system - Multiple fixes to polydots 5.3.3 No changes 5.3.2 - Added types for control operators - Added `typed/untyped-utils` 5.3.1 - Revised handling of `Any` exported to untyped code - Added `cast` - Correctly compute variance of polymorphic type application 5.3 - Keyword and optional arguments - Faster startup - Random testing of the numeric tower 5.2.1 - Inference of functions with keyword arguments - `typecheck-fail' for explicit creation of type errors - Extensive documentation of typed numeric tower 5.2 - Performance work: delayed environment evaluation - Support `racket'-style optional arguments - Changes to support new-style keyword argument expansion