Racket 6.0.1 发布，此版本现已提供下载，更新内容如下：
A new racket/undefined library exports undefined as the value currently produced by
(letrec ([x x]) x)
The drawing and GUI libraries provide improved support for high-resolution bitmaps and their use on Retina displays.
Check Syntax cooperates with Typed Racket to show arrows and other Check Syntax highlighting even when there is a type error.
Functions provided via contract-out that have first-order contracts perform better.
The contract boundary between typed/untyped modules is much less expensive.
Occurrence typing now works better with when/unless. Example:
(let ((x (read)))
(unless (number? x) (error 'bad-input))
(add1 x))
Types in Typed Racket are now pretty-printed.
Function types can now be written in prefix style, which is now preferred and is used for printing.
A new ->* type constructor is used for writing types for functions with optional and keyword arguments.
Typed Racket forms do not have a : suffix by default now.
Typed Racket now has preliminary support for classes and objects.
Type aliases in Typed Racket now support recursion and mutual recursion.
Plot correctly renders intersecting 3D graphs and non-grid-aligned 3D rectangles.
Elements in plots output in PDF/PS format have the same relative scale as in other formats.
更多更新内容请看发行说明。
Racket源自著名的专家型语言PLT Scheme，同时又是Lisp语言的一个分支。它适用于从脚本Script到应用程序开发的任务执行工具，包括图形用户界面，Web服务器等。支持编译器的虚拟机，创建独立的可执行程序的工具，Racket Web服务器，具有丰富而全面的功能库，适用于初学者和专家编程。
项目主页：http://blog.racket-lang.org/2014/05/racket-v601.html
下载地址：http://download.racket-lang.org/
来自:开源中国社区
