Release Announcement for Version 7.4

Racket v7.4

Racket version 7.4 is now available from

With this 7.4 release, we are making Racket CS available, a beta version
of the Racket on Chez Scheme implementation.  Racket CS is "beta"
quality for the v7.4 release. It works well enough to be worth trying,
but there are likely too many lingering problems for a project to switch
to Racket CS for production use at this time. We encourage you to kick
the tires of the new CS releases, and to help push this project forward
by reporting any problems that you find.

- Racket CS is available as a download option. To download Racket CS,
  select "CS (beta)" instead of "regular" from the "Variant" popup menu.

- Single-precision floating-point literals, a.k.a. single-flonums, are
  no longer supported by default.

  This is a backward-incompatible change, but the use of single-flonums
  appears to be rare. Since Racket CS does not support single-flonums,
  disabling single-flonums by default smooths the transition from regular
  Racket and Racket CS.

  The `read-single-flonum` parameter can be set to #t to enable reading
  single-flonum literals, but a better strategy in most cases is to use
  `real->single-flonum` when `single-flonum-available?` reports #t or
  when `single-flonum?` reports #t for a value (which implies that
  single-flonums must be supported). Where single-flonums are supported,
  Racket's compiler will fold a call of `real->single-flonum` on a
  literal number to a constant single-flonum value.

- New compilation flags including --disable-generations and --enable-ubsan
  provide better support for alternative

- The 2htdp/universe teachpack supports an event log window for big-bang. 
  With this option, students can inspect the events that big-bang handled,
  plus their payload. The event log includes messages from external

The following people contributed to this release: Alex Knauth, Alexander
B. McLin, Alexis King, Andreas Düring, Asumu Takikawa, Atharva Raykar,
Ben Greenman, Benjamin Yeung, Dmitry Moskowski, Fred Fu, Gustavo
Massaccesi, Ilnar Salimzianov, Jason Hemann, Jay McCarthy, Jesse A. Tov,
Jesse Alama, John Clements, Leif Andersen, Lukas Lazarek, Matthew Flatt,
Matthias Felleisen, Mike Sperber, Morgan Lemmer-Webber, Noah W M, Paulo
Matos, Philip McGrath, Robby Findler, Rodrigo, Roman Klochkov, Ryan
Culpepper, Sam Tobin-Hochstadt, Simon 'Sze' L. Schlee, Sorawee
Porncharoenwase, Spencer Florence, Stephan Renatus, Stephen Chang,
Stephen De Gabrielle, Thomas Dickerson, Vincent St-Amour, yjqww6