在#haskell@freenode中使用lambdabot

IRC可不只是闲聊的地方，她是你随时可用的好工具。IRC中有很多Bot可以随时为你服务。这里只收集了在#haskell@freenode中使用的lambdabot。（为了不影响别人，你最好发私信： /msg lambdabot ...）

查hoogle：

ERC> @hoogle applicative

<lambdabot> Control.Applicative class Functor f => Applicative f
<lambdabot> Control.Applicative module Control.Applicative
<lambdabot> package applicative-extras

查类型：

ERC> @type (<*>)

<lambdabot> Applicative f => f (a -> b) -> f a -> f b

运算：

ERC> > map ((&&) <$> (>3) <*> (<5)) [1..9]

<lambdabot> [False,False,False,True,False,False,False,False,False]

ERC> @let a...b = [a..b]
<lambdabot> Defined.
> 1...20
<lambdabot> [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

大家知道do是语法糖，可用@undo还原：

ERC> @undo do { Just y <- x; z }

<lambdabot> x >>= \ a -> case a of { Just y -> z; _ -> fail ""}

查实例：

@instances Monad
<lambdabot> ArrowMonad a, ContT r m, ErrorT e m, IO, Maybe, RWST r w s m,
ReaderT r m, ST s, StateT s m, WriterT w m, []

查源码：

ERC> @src (<$>)

<lambdabot> f <$> a = fmap f a

ERC> @src foldr
<lambdabot> foldr f z [] = z
<lambdabot> foldr f z (x:xs) = f x (foldr f z xs)

ERC> @src foldl
<lambdabot> foldl f z [] = z
<lambdabot> foldl f z (x:xs) = foldl f (f z x) xs

ERC> @src Monad
<lambdabot> class Monad m where
<lambdabot> (>>=) :: forall a b. m a -> (a -> m b) -> m b
<lambdabot> (>>) :: forall a b. m a -> m b -> m b
<lambdabot> return :: a -> m a
<lambdabot> fail :: String -> m a

ERC> @source Data.List
<lambdabot> http://darcs.haskell.org/packages/base/Data/List.hs

看看是否有现成函数：
ERC> @pl fn op g k a = g a `op` k a
<lambdabot> fn = liftM2

fn 其实就是 liftM2 。 liftM2 是专门用来把二元函数提升到 Monad 中去的，而 ((->) a) 正是 Monad 的实例。

Djinn通过type signature构造函数： 

@djinn (a, b) -> c -> (b, c) ==> f (_, a) b = (a, b) 

查一个monad transformer包装的类型：

@unmtl StateT s IO a ==> s -> IO (a, s)

查网址：

ERC> @where lyah
<lambdabot> http://www.learnyouahaskell.com/

ERC> @where rwh
<lambdabot> http://www.realworldhaskell.org/blog/
  http://book.realworldhaskell.org/read/

ERC> @where wikibook
<lambdabot> http://en.wikibooks.org/wiki/Haskell

ERC> @where hackage
<lambdabot> <http://hackage.haskell.org/package/>

ERC> @where hackage-mirror
<lambdabot> remote-repo:
    hdiff.luite.com:http://hdiff.luite.com/packages/archive/

ERC> @where xmonad

<lambdabot> http://xmonad.org/

查软件包：

@hackage repa
<lambdabot> http://hackage.haskell.org/package/repa

查单词：

ERC> @wn applicative

<lambdabot> *** "applicative" wn "WordNet (r) 3.0 (2006)" [13:46]
<lambdabot> applicative
<lambdabot> adj 1: readily applicable or practical [syn: {applicative},
<lambdabot> {applicatory}]