Racket v5.0.2

Racket version 5.0.2 is now available from

  http://racket-lang.org/

• Typed Racket's optimizer is now turned on by default; error messages have been simplified and clarified.
• Contracts: contracts on mutable containers allow functions or other higher order values, and contracts are checked when updating or dereferencing the containers. The new contracts are slower than the old ones, so the old check-once functionality is still available.
  A new dependent function contract combinator, ->i, properly assigns blame for contracts that violate themselves and the generated wrappers are more efficient than ->d. (Although it does more checking so your contracts may be faster or slower).
  See the docs for box/c, hash/c, vector/c, vectorof and ->i for more details.
• The when, unless, cond, case, and match forms (in racket/base and derived languages) now allow immediate internal definitions.
• Web server: the formlets library provides more HTML form elements; make-xexpr-response supports a preamble for DTD declarations; serve/servlet supports stateless servlets.
• New WebSocket implementation, see net/websocket for details.
• The new data collection contains implementations of several data structures, including growable vectors and order-based dictionaries.
• racket/match is now significantly faster.
• The Racket documentations are built in parallel by default.
• The stepper is now compatible with programs using the Universe teachpack.
• 2htdp/image: pinholes are now supported in the library (if you don't use pinhole primitives you will not see them); a number of new triangle functions added; supports conversion of images to color lists and back. Also, cropping has been improved for scenes; see the documentation section on the nitty-gritty of pixels for details.
• Signatures have been moved to ASL, BSL, BSL+, ISL, and ISL+ (HtDP teaching languages) no longer support checked signatures.
• Student languages: one-armed check-error in all levels; ASL is extended with hash operations, and define-datatype.
• DMdA languages: Checking for parametric signatures is now eager. This catches errors earlier, but retains the asymptotic complexity properties; signatures for record types now have generators; list-of and any signatures are now provided.