Racket v8.4 released

[John Clements]

Racket version 8.4 is now available from

https://racket-lang.org/



* Command-line Racket provides a new expression editor by default for
its read-eval-print loop (REPL). The new REPL is based on the Chez
Scheme expression editor, but extended to use the same
language-sensitive syntax coloring and indentation tools as DrRacket.

* Typed Racket adds a kind system, preventing programmers from
writing nonsensical type expressions. It checks whether type
constructors are correctly applied to arguments, and separates
type constructors from polymorphic types. The `:kind` form enables
checking the kind of a type expression at the REPL. The new system
also correctly rejects some ill-formed recursive types.

* Racket has a `file-or-directory-stat` for unified information about
file-system objects.

* DrRacket shows the region affected by an `#;` S-expression comment
by fading the commented-out region.

* Racket on Chez has faster multiplication and division for some
numbers.

* Web server: The files dispatcher supports all standard caching-related
HTTP response headers (e.g., Cache-Control).

* Web server: A new dispatcher captures the common pattern of processing
HTTP requests and responses in a layered fashion.

* The Web Server supports use of the Cache-Control header, and includes
a new wrapping dispatcher.

* Expander: add "portal" syntax to support new forms of syntax object
binding.

* Documentation search is improved.

* Some hash operations support an optional `try-order?` argument.

* The plot-metrics interface has documentation.

* Fonts support OpenType feature settings.

* The Gui library has improved support for Wayland.

* The computation of quadratic roots is further improved.

* The `set/c` contract adds support for random generation.

* DrRacket's interactions window supports #lang-specific coloring
and indentation.

* DrRacket's parenthesis-based keyboard shortcuts change based on
the parentheses that each different #lang uses.

* The release includes many other bug repairs and other improvements!

Transition/Update notes:

* To turn off expeditor and make Racket's REPL go back to the old
editline/readline-based editor, use the command

,input readline

and then restart Racket. Get back to the new expression editor with

,input expeditor

To toggle color mode for the new expression editor, use one of the
following, which does not require restarting Racket:

,color #false
,color #true

* Support for comment fading in DrRacket requires an increment to
the "WXME" format version so files with non-text content written
by DrRacket v8.4 will open only in v8.4 and later. This does not
affect files that consist only of unicode text.

* The addition of the kind system to Typed Racket means that certain
mild abuses of the type system no longer type check, most notably
the 'application' of a polymorphic type.


The following people contributed to this release:

Alex Harsányi, Alex Knauth, Alexander Shopov, Alexis King, Andrew
Mauer-Oats, Andy Keep, Ayman Osman, Ben Greenman, Bob Burger, Bogdan
Popa, Cameron Moy, D. Ben Knoble, Fred Fu, Greg Hendershott, Gustavo
Massaccesi, Jamie Taylor, Jarhmander, Jesse Alama, Joel Dueck, John
Clements, Jordan Johnson, Laurent Orseau, Leif Andersen, Marc Burns,
Matthew Flatt, Matthias Felleisen, Mike Engelhart, Mike Sperber, Noah
Ma, Oscar Waddell, Pavel Panchekha, Philip McGrath, rgkirch, Robby
Findler, Sam Tobin-Hochstadt, Sergiu Ivanov, Sorawee Porncharoenwase,
Stefan Schwarzer, Stephen De Gabrielle, Tony Garnock-Jones, Viko Riféo,
and Zachary Mao



Link to package regressions issue for the 8.4 release:
https://github.com/racket/racket/issues/4125

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