[racket-dev] Release Announcement for v6.0.1

At Thu, 01 May 2014 13:49:55 -0400, Ryan Culpepper wrote:
> mflatt:
> - 2x bitmaps (037a211f, e47a90cc, etc); file/convertible (eda4f357)
> - retina displays (7dc63162)
> - dc alignment scale (582e9925)
> - bignum performance (780d6ae5)
> - added syntax/wrap-modbeg (bfda0665)
> - treat FFI primitives like other primitives (eff53cde)
> - add PLTUSERHOME (e4ce0d03)
> - fix bignum allocation (efa19918)
> - add racket/undefined (8abf7825, 74f82bbd)


 * A new `racket/undefined` library exports `undefined` as the
   value currently produced by

       (letrec ([x x]) x)

   This library anticipates a future where that expression will raise
   an exception. The `racket/undefined` library will continue to offer
   the `undefined` value as a bridge between versions and as a last
   resort.

 * The drawing and GUI libraries provide improved support for
   high-resolution bitmaps and their use on Retina displays. For
   example, `read-bitmap` includes a `#:try- at 2x?` option to trigger
   substitutions through the usual "@2x" naming convention.