/learn-haskell

Haskell 学习

Primary LanguageHaskell

Haskell练习

Date: 02/13 2016

Contents

官网: https://www.haskell.org/

包: https://hackage.haskell.org/

安装环境

安装 Haskell 编译器:

# OS X
brew install ghc
# Linux (Debian)
sudo apt-get install ghc ghci

Haskell 内建包管理器:

ghc-pkg list
admin@Work ~/.cabal> ghc-pkg list
WARNING: cache is out of date: /usr/local/Cellar/ghc/7.10.3b/lib/ghc-7.10.3/package.conf.d/package.cache
ghc will see an old view of this package db. Use 'ghc-pkg recache' to fix.
/usr/local/Cellar/ghc/7.10.3b/lib/ghc-7.10.3/package.conf.d
   Cabal-1.22.5.0
   array-0.5.1.0
   base-4.8.2.0
   bin-package-db-0.0.0.0
   binary-0.7.5.0
   bytestring-0.10.6.0
   containers-0.5.6.2
   deepseq-1.4.1.1
   directory-1.2.2.0
   filepath-1.4.0.0
   ghc-7.10.3
   ghc-prim-0.4.0.0
   haskeline-0.7.2.1
   hoopl-3.10.0.2
   hpc-0.6.0.2
   integer-gmp-1.0.0.0
   pretty-1.1.2.0
   process-1.2.3.0
   rts-1.0
   template-haskell-2.10.0.0
   terminfo-0.4.0.1
   time-1.5.0.1
   transformers-0.4.2.0
   unix-2.7.1.0
   xhtml-3000.2.1
/Users/admin/.ghc/x86_64-darwin-7.10.3/package.conf.d
   HTTP-4000.3.3
   mtl-2.2.1
   network-2.6.2.1
   network-uri-2.6.0.3
   parsec-3.1.9
   text-1.2.2.0

Haskell 内建函数包:

ghc-pkg list ghc
WARNING: cache is out of date: /usr/local/Cellar/ghc/7.10.3b/lib/ghc-7.10.3/package.conf.d/package.cache
ghc will see an old view of this package db. Use 'ghc-pkg recache' to fix.
/usr/local/Cellar/ghc/7.10.3b/lib/ghc-7.10.3/package.conf.d
   ghc-7.10.3
/Users/admin/.ghc/x86_64-darwin-7.10.3/package.conf.d

找到 ghc-7.10.3 这个包（后面的数字是 GHC 版本号，视具体版本而定）：

cabal info ghc-7.10.3

查看 GHC 内建包中的函数函数及模块列表: https://downloads.haskell.org/~ghc/latest/docs/html/libraries/index.html

安装 Hackage 包管理器 cabal:

# OS X
brew install cabal
cabal init
cabal install base HTTP unix network
# 包缓存在 `~./.cacbl` 目录

代码编译

编译二进制或者字节码:

ghc -o helloworld helloworld.hs

进入解释器交互模式:

ghci

书籍《Real World Haskell》

Haskell 操作符 以及 语法标记

Haskell Operators and other Lexical Notation

-- Start of comment line
{- Start of short comment
-} End of short comment
+ Add operator
- Subtract/negate operator
* Multiply operator
/ Division operator
Substitution operator, as in e{f/x}
^, ^^, ** Raise-to-the-power operators
&& And operator
|| Or operator
< Less-than operator
<= Less-than-or-equal operator
== Equal operator
/= Not-equal operator
>= Greater-than-or-equal operator
> Greater-than operator
\ Lambda operator
. Function composition operator
Name qualifier
| Guard and case specifier
Separator in list comprehension
Alternative in data definition (enum type)
++ List concatenation operator
: Append-head operator (“cons”)
!! Indexing operator
.. Range-specifier for lists
\\ List-difference operator
<- List comprehension generator
Single assignment operator in do-constr.
; Definition separator
-> Function type-mapping operator.
Lambda definition operator
Separator in case construction
= Type- or value-naming operator
:: Type specification operator, “has type”
=> Context inheritance from class
() Empty value in IO () type
>> Monad sequencing operator
>>= Monad sequencing operator with value passing
>@> Object composition operator (monads)
(..) Constructor for export operator (postfix)
[ and ] List constructors, “,” as separator
( and ) Tuple constructors, “,” as separator
Infix-to-prefix constructors
‘ and ‘ Prefix-to-infix constructors
’ and ’ Literal char constructors
" and " String constructors
_ Wildcard in pattern
~ Irrefutable pattern
! Force evaluation (strictness flag)
@ “Read As” in pattern matching

内建函数（Built-in Functions）

参考:

《The Glorious Glasgow Haskell Compilation System User's Guide, Version 6.6》 中提到的 GHC Libraries:

内建类型和类（Predefined Types and Classes）

参考:

高阶函数（Higher Order Functions）

参考： Higher order functions - map, fold and filter

你好，世界

import System.IO

main = do
    System.IO.putStrLn "Hello, 世界！"
    System.IO.putStr "Hello, 世界！\n"