Difference between revisions of "Cn/Haskell in 5 steps"

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</haskell>
  
</haskell>
   
  +
<!--
 
This defines a new function called '''fac''' which computes the
  
This defines a new function called '''fac''' which computes the
 
factorial of an integer.
  
factorial of an integer.
  +
-->
  +
以上定义了一个阶乘函数 '''fac'''。
   
  +
<!--
 
We can now run '''fac''' on some argument:
  
We can now run '''fac''' on some argument:
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-->
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We can now run '''fac''' on some argument:
  +
 
<haskell>
  
<haskell>
 
Prelude> fac 42
  
Prelude> fac 42
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</haskell>
  
</haskell>
   
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<!--
 
'''Congratulations!''' Programming made easy. Note that if you're using
  
'''Congratulations!''' Programming made easy. Note that if you're using
  +
Hugs, you'll need to load the definition of '''fac''' from a file,
  +
'''fac.hs''', containing:
  +
-->
  +
'''Congratulations!''' Programming made easy. 注意，if you're using
 
Hugs, you'll need to load the definition of '''fac''' from a file,
  
Hugs, you'll need to load the definition of '''fac''' from a file,
 
'''fac.hs''', containing:
  
'''fac.hs''', containing:
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</haskell>
  
</haskell>
   
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<!--
 
And run it with Hugs as follows (this also works in GHCi):
  
And run it with Hugs as follows (this also works in GHCi):
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-->
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如下运行之：（GHCi 同样有效）
   
 
<haskell>
  
<haskell>
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</haskell>
  
</haskell>
   
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<!--
 
We can of course compile this program, to produce a standalone
  
We can of course compile this program, to produce a standalone
 
executable. In the file '''fac.hs''' we can write (and let's use
  
executable. In the file '''fac.hs''' we can write (and let's use
  +
elegant pattern matching syntax just for fun):
  +
-->
  +
亦可编译之，生成可执行档。In the file '''fac.hs''' we can write (and let's use
 
elegant pattern matching syntax just for fun):
  
elegant pattern matching syntax just for fun):
   
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</haskell>
  
</haskell>
   
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<!--
 
which can then be compiled and run:
  
which can then be compiled and run:
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-->
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然后编译运行：
   
 
<pre>
  
<pre>
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'''Great!'''
  
'''Great!'''
   
  +
<!--
 
== Where to go from here ==
  
== Where to go from here ==
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-->
  +
== 更上一层楼 ==
   
  +
<!-
 
There are many good Haskell tutorials and books. Here are some we recommend:
  
There are many good Haskell tutorials and books. Here are some we recommend:
  +
-->
  +
有很多很好的 Haskell 教程和图书。推荐：
   
  +
<!--
 
'''Tutorials'''
  
'''Tutorials'''
 
* [[Learn_Haskell_in_10_minutes|Haskell in 10 minutes]]
  
* [[Learn_Haskell_in_10_minutes|Haskell in 10 minutes]]
  +
* [http://darcs.haskell.org/yaht/yaht.pdf Yet Another Haskell Tutorial] (English)
  +
* [http://www.haskell.org/tutorial/ A Gentle Introduction to Haskell] (English, [[Image:GentleFR.pdf|French PDF]])
  +
-->
  +
'''教程'''
  +
* [[Learn_Haskell_in_10_minutes|十分钟学会 Haskell]] ([[cn/十分钟学会 Haskell|中]])
 
* [http://darcs.haskell.org/yaht/yaht.pdf Yet Another Haskell Tutorial] (English)
  
* [http://darcs.haskell.org/yaht/yaht.pdf Yet Another Haskell Tutorial] (English)
 
* [http://www.haskell.org/tutorial/ A Gentle Introduction to Haskell] (English, [[Image:GentleFR.pdf|French PDF]])
  
* [http://www.haskell.org/tutorial/ A Gentle Introduction to Haskell] (English, [[Image:GentleFR.pdf|French PDF]])
   
  +
<!--
 
For a complete list of textbooks, references and tutorials:
  
For a complete list of textbooks, references and tutorials:
  +
-->
  +
图书、资料、教程的完整列表：
   
  +
<!--
 
* [[Books and tutorials]]
  
* [[Books and tutorials]]
  +
-->
  +
* [[图书和教程]]
   
  +
<!--
 
'''Join the community!'''
  
'''Join the community!'''
  +
-->
  +
'''加入社区！'''
   
  +
<!--
 
Talk to others in the Haskell community:
  
Talk to others in the Haskell community:
  +
-->
  +
与 Haskell 社区成员交流：
   
  +
<!--
 
* [http://haskell.org/mailman/listinfo/haskell-cafe Haskell-Cafe mailing list]
 
* [http://haskell.org/mailman/listinfo/haskell-cafe Haskell-Cafe mailing list]
 
* [[IRC channel]]
  
* [[IRC channel]]
  +
-->
  +
* [http://haskell.org/mailman/listinfo/haskell-cafe Haskell-Cafe 邮件列表]
  +
* [[IRC 频道]]
   
 
[[Category:Tutorials]]
  
[[Category:Tutorials]]
−
Languages: [[5 adımda Haskell|tur]] [[cn/Haskell in 5 steps|zh/cn]]
 +
Languages: [[Haskell in 5 steps|en]] [[5 adımda Haskell|tur]] [[cn/Haskell in 5 steps|zh/cn]]

Revision as of 11:25, 14 December 2007

Haskell 是一门通用型纯粹函数式编程语言。 此篇将引导你尽快上路。

安装 Haskell

类似其他语言，Haskell 提供了两种风格的处理方式：批处理（“编译器”）和交互式（“解释器”）。 其中解释器可直接用于测试和计算，是初学者的好帮手。

GHC 编译器和解释器（GHCi） 可能是特性实现最全面的系统
Hugs 解释器 高度可移植，轻量级

GHC 和 Hugs 都可以在 Windows 上工作，Hugs 似乎和此平台配合得更好。 在 Mac OS X 上安装 Haskell。

运行 Haskell

启动一个终端。 如果安装了 GHC，在命令行输入 ghci （GHC 解释器的可执行文件名）。 如果安装了 Hugs，输入 hugs。 

    $ ghci
       ___         ___ _
      / _ \ /\  /\/ __(_)
     / /_\// /_/ / /  | |      GHC Interactive, version 6.4, for Haskell 98.
    / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
    \____/\/ /_/\____/|_|      Type :? for help.

    Loading package base-1.0 ... linking ... done.
    Prelude>

现在你看到一个提示符，Haskell 系统期候你的输入。

第一个 Haskell 程序

如果学习过其他编程语言，你的第一个程序可能就是 "Hello, world!"。我们可以这样： 

Prelude> "Hello, World!"
"Hello, World!"

Haskell 系统对此字符串求值，并输出结果。 稍加修改，可以直接输出到标准输出： 


Prelude> putStrLn "Hello World"
Hello World

通过 Haskell 编译器，如 GHC，可以把代码编译成单独的可执行档。 新建源文件 hello.hs，包含： 


main = putStrLn "Hello, World!"

编译之： 

    $ ghc -o hello hello.hs

运行之（Unix 系统上用 ./hello，Windows 系统用 hello.exe）： 

    $ ./hello
    Hello, World!

Haskell 计算器

Let's do something fun. 你的第一个真正的程序是阶乘函数。回到解释器，定义之： 

Prelude> let fac n = if n == 0 then 1 else n * fac (n-1)

以上定义了一个阶乘函数 fac。

We can now run fac on some argument: 

Prelude> fac 42
1405006117752879898543142606244511569936384000000000

Congratulations! Programming made easy. 注意，if you're using Hugs, you'll need to load the definition of fac from a file, fac.hs, containing: 

fac n = if n == 0 then 1 else n * fac (n-1)

如下运行之：（GHCi 同样有效） 

Hugs.Base> :load fac.hs
Main> fac 42
1405006117752879898543142606244511569936384000000000

亦可编译之，生成可执行档。In the file fac.hs we can write (and let's use elegant pattern matching syntax just for fun): 

fac 0 = 1
fac n = n * fac (n-1)

main = print (fac 42)

然后编译运行： 

    $ ghc -o fac fac.hs
    $ ./fac
    1405006117752879898543142606244511569936384000000000

Great!

更上一层楼

<!- There are many good Haskell tutorials and books. Here are some we recommend: --> 有很多很好的 Haskell 教程和图书。推荐：

教程

图书、资料、教程的完整列表：

加入社区！

与 Haskell 社区成员交流：

Languages: en tur zh/cn

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