* 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
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
* 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
* `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
* `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.