ghc 7.0.1 发布

编译了一个，有很多有意思的东西

Release Note在此。列举几处我比较有兴趣的：

• 基于 epoll/kqueue 的IO
• 可以生成 LLVM 代码
• 翻新了大量模块，特别是线程或异常阻塞有关的
• ghci 现在完整支持 import
• 支持 haskel 2010 ，但是新标准可能会与传统的 base 模块冲突，建议使用ghc/ghci时用以下命令屏蔽冲突模块：

ghci -package haskell2010 -hide-package base -hide-package array

• 现在支持 utf8 编码的源码文件，以及，甚至有一些 unicode 字符可以直接成为语法的一部分。
• GC 固定为两代回收
• 现在 ghc 可以向操作系统归还内存（至少 Python 和 Java 都还不能，C 的 free 在这方面也不是很有效）。
• 优化了 ghci 的沙盒

我在 ghci 里 :help 了一下，内容跟以前非常不同了。如下所示，有几个功能非常有爱，如：

• 可以支持多行
• 能够生成 etags 和 ctags

*Main> :help
 Commands available from the prompt:

   <statement>                 evaluate/run <statement>
   :                           repeat last command
   :{/n ..lines.. /n:}/n       multiline command
   :add [*]<module> ...        add module(s) to the current target set
   :browse[!] [[*]<mod>]       display the names defined by module <mod>
                               (!: more details; *: all top-level names)
   :cd <dir>                   change directory to <dir>
   :cmd <expr>                 run the commands returned by <expr>::IO String
   :ctags[!] [<file>]          create tags file for Vi (default: "tags")
                               (!: use regex instead of line number)
   :def <cmd> <expr>           define a command :<cmd>
   :edit <file>                edit file
   :edit                       edit last module
   :etags [<file>]             create tags file for Emacs (default: "TAGS")
   :help, :?                   display this list of commands
   :info [<name> ...]          display information about the given names
   :kind <type>                show the kind of <type>
   :load [*]<module> ...       load module(s) and their dependents
   :main [<arguments> ...]     run the main function with the given arguments
   :module [+/-] [*]<mod> ...  set the context for expression evaluation
   :quit                       exit GHCi
   :reload                     reload the current module set
   :run function [<arguments> ...] run the function with the given arguments
   :type <expr>                show the type of <expr>
   :undef <cmd>                undefine user-defined command :<cmd>
   :!<command>                 run the shell command <command>

 -- Commands for debugging:

   :abandon                    at a breakpoint, abandon current computation
   :back                       go back in the history (after :trace)
   :break [<mod>] <l> [<col>]  set a breakpoint at the specified location
   :break <name>               set a breakpoint on the specified function
   :continue                   resume after a breakpoint
   :delete <number>            delete the specified breakpoint
   :delete *                   delete all breakpoints
   :force <expr>               print <expr>, forcing unevaluated parts
   :forward                    go forward in the history (after :back)
   :history [<n>]              after :trace, show the execution history
   :list                       show the source code around current breakpoint
   :list identifier            show the source code for <identifier>
   :list [<module>] <line>     show the source code around line number <line>
   :print [<name> ...]         prints a value without forcing its computation
   :sprint [<name> ...]        simplifed version of :print
   :step                       single-step after stopping at a breakpoint
   :step <expr>                single-step into <expr>
   :steplocal                  single-step within the current top-level binding
   :stepmodule                 single-step restricted to the current module
   :trace                      trace after stopping at a breakpoint
   :trace <expr>               evaluate <expr> with tracing on (see :history)

 -- Commands for changing settings:

   :set <option> ...           set options
   :set args <arg> ...         set the arguments returned by System.getArgs
   :set prog <progname>        set the value returned by System.getProgName
   :set prompt <prompt>        set the prompt used in GHCi
   :set editor <cmd>           set the command used for :edit
   :set stop [<n>] <cmd>       set the command to run when a breakpoint is hit
   :unset <option> ...         unset options

  Options for ':set' and ':unset':

    +r            revert top-level expressions after each evaluation
    +s            print timing/memory stats after each evaluation
    +t            print type after evaluation
    -<flags>      most GHC command line flags can also be set here
                         (eg. -v2, -fglasgow-exts, etc.)
                    for GHCi-specific flags, see User's Guide,
                    Flag reference, Interactive-mode options

 -- Commands for displaying information:

   :show bindings              show the current bindings made at the prompt
   :show breaks                show the active breakpoints
   :show context               show the breakpoint context
   :show modules               show the currently loaded modules
   :show packages              show the currently active package flags
   :show languages             show the currently active language flags
   :show <setting>             show value of <setting>, which is one of
                                  [args, prog, prompt, editor, stop]