- The case form dispatches on characters, fixnums, symbols, and keywords in logarithmic time. (Thanks to Jon Zeppieri.)
- The new racket/format library provides new and improved string-formatting functions.
- Logging tools include improved filtering support based on the name of a logger. A new define-logger form simplifies the use of named loggers. Forms such as log-debug now support string formatting.
- The for forms now support #:break and #:final clauses.
- The new PLTCOMPILEDROOTS environment variable configures the search path for compiled bytecode.
- Check Syntax now summarizes the documentation (i.e., the blue boxes) for the identifier at the insertion point in the top-right corner of the definitions window.
- Check Syntax now runs continuously for programs that declare their language within the source. This mode has been available for several of the past releases, but now enabled by default.
- DrRacket can spell-check string constants (enable this in the Edit menu).
- Typed Racket interprets the Any type as a different contract. This may signal dynamic errors in some existing mixed typed/untyped programs. The normal fix is to replace a use of Any with a more specific types.
- NaN is included in all of Typed Racket's floating-point types, which makes precise floating-point types easier to use.
- Typed Racket supports a cast operation with support for higher-order types.
- Typed Racket provides the :query-type/args and :query-type/result utilities to explore types at the REPL.
- The compatibility collection provides features from Racket relatives, such as defmacro and mutable lists. These features are provided to ease porting code to Racket. Avoid them in modern Racket code.
- Screenshots of the widgets provided by the Racket GUI library are included in the documentation. (Thanks to Diogo F. S. Ramos.)
- FrTime was ported to racket #lang. (Thanks to Patrick Mahoney.)
The following has been deprecated and will be removed in the January 2013 release:
- the planet command-line tool; use raco planet instead.
The following has been deprecated and will be removed in the August 2013 release:
- the mzlib/class100 library; use racket/class instead.