[Racket announcement] Racket v6.8

From: Vincent St-Amour (stamourv at eecs.northwestern.edu)
Date: Tue Jan 24 16:05:15 EST 2017		 
Racket version 6.8 is now available from

    http://racket-lang.org/

- Racket sports a new logo, courtesy of Matthew Butterick.

- MacBook Pro laptops with touch bars are supported.

- Support for FreeBSD on PowerPC.

- Initial support for GTK3 on Wayland is available. GL contexts, GC
  blits, and dialog placement currently do not work.

- The macro stepper provides a command-line interface via the
  `raco macro-stepper` command.

- Typed Racket more efficiently represents and computes types and
  propositions, resulting in faster type checking for many programs.
  For more details, see this blog post by Andrew Kent:
  https://pnwamk.github.io/blog/2017/01/08/some-changes-in-typed-racket-v6-8/

- The bytecode optimizer can reduce more expressions of the form
  `(equal? x y)` to `(eqv? x y)` or `(eq? x y)` when the type of `x` or
  `y` is known.

- The bytecode optimizer avoids dropping stack frames in some reductions.
  This provides better stack traces for errors when errotrace is enabled.

- The bytecode compiler detects more optimization opportunities,
  including when variables always hold a boolean value. In particular in
  expressions like `(or (symbol? x) (something))`, the optimizations
  avoid the creation of an intermediate variable to store the result of
  `(symbol? x)`.

- The `syntax` form preserves syntax properties on all template pieces.

- The `scribble/html/extra` module provides renderers for HTML elements
  that are part of the WHATWG HTML standard but not part of the `scribble/html`
  language by default (e.g., `map`, `time`, `video`).

- The DeinProgramm teaching languages support pattern matching using the
  `match` form.

- In the DeinProgramm languages, `define-record-procedures` supports
  specifying signatures as part of the form, instantly enabling
  properties quantifying over such records.

The following people contributed to this release:
Aleksej Saushev, Alex Knauth, Alexander Hedges, Alexander Shopov, Alexis
King, Andrew Kent, Asumu Takikawa, Ben Greenman, Celeste Hollenbeck,
Craig Allen, Don March, Georges Dupéron, Gustavo Massaccesi, James
Bornholt, Jay McCarthy, Jerry James, John Clements, Juan Francisco
Cantero Hurtado, Leandro Facchinetti, Leif Andersen, Matthew Butterick,
Matthew Flatt, Matthias Felleisen, Max New, Mike Sperber, Phil Nguyen,
Reid D McKenzie, Reuben Thomas, Robby Findler, Ryan Culpepper, Sam
Tobin-Hochstadt, Shu-Hung You, Spencer Florence, Stephen Chang, Tim
Brown, Tony Garnock-Jones, Vincent St-Amour, WarGrey Gyoudmon Ju, and
William G Hatch.

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