Racket 6.2 发布，Lisp 语言分支

akyou56

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　　Racket 6.2 发布了，在这个版本中我们对核心库进行了优化和减缩，并将代码迁移到 Github 上。
　　目前核心库的源码请看 https://github.com/plt/racket, 和扩展包的源码 https://github.com/racket/.
　　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。
　　其他改进内容包括：
　　core repo
　　
　　* The package manager supports a direct references to Git repositories
　　via "git://[...]", "http://[...].git", and "https://[...].git" URLs.
　　(Previously, only references to GitHub were supported.)
　　
　　* A `--clone` option for `raco pkg install` or `raco pkg update`
　　facilitates Git-based package development. If a package X has a Git
　　repository source, installing and updating the package pulls from the
　　repository in a read-only mode. Using `raco pkg update --clone X`
　　switches the local installation to a repository checkout that is
　　suitable for modifying the package implementation, issuing pull
　　requests, pushing changes, and so on.
　　
　　Using `raco pkg update --lookup X` switches the package back to the
　　default installation mode.
　　
　　drracket
　　
　　* Its on-line check syntax works with graphical content.
　　
　　* Increased availability of DrRacket's blueboxes, including method and
　　constructor information.
　　

　　* The "Open Require Path" menu item supports ".." in>　　
　　data
　　
　　* Added data/enumerate, a library that supports efficient enumeration of
　　data structures
　　
　　redex
　　
　　* Its redex-check facility uses data (in addition to random) enumeration
　　to try to find counter-examples.
　　
　　* Its generate-term function accepts additional arguments to return the
　　"i"-th member of a pattern using data/enumerate (meaning it
　　efficiently supports very large values of "i").
　　
　　* The examples collection includes Launchbury's 1993 big-step lazy
　　semantics.
　　
　　htdp
　　
　　* 2htdp/image's polygon may be built out of bezier curves instead of
　　just straight lines (see the docs for "pulled-point").
　　
　　* 2htdp/abstraction is a teachpack for instructors and students who wish
　　to use for/* loops, match, define-type and type-cases in ISL and ISL+.
　　
　　* 2htdp/universe programs can be exported using DrRacket's executable
　　creation mechanism and they behave properly when run independently.
　　
　　typed-racket
　　
　　* Typed Racket in DrRacket displays tooltips that show the types of
　　expressions. Tooltips are also displayed for type errors.
　　
　　* Typed Racket loads generated contracts only when needed. This reduces
　　memory use and startup time for Typed Racket programs.
　　
　　* Typed Racket has improved support for prefab structures, future
　　semaphores, and async channels.
　　
　　* Typed Racket understands when two different variables refer to the
　　same thing, and updates types accordingly. This particularly improves
　　the type checking of macros such as `match`