meetlai

import Data.List
import Control.Monad

valid xs = any ((== max) . sum)  $ filterM (const [True, False]) left where
    max = maximum xs
    left = delete max xs

main = do
    print $ valid [4, 6, 23, 10, 1, 3]
    print $ valid [5, 7, 16, 1, 2]

meetlai

(let ((yin ((lambda (foo) (newline) foo) (call/cc (lambda (bar) bar))))  
      (yang ((lambda (foo) (write-char #\*) foo) (call/cc (lambda (bar) bar)))))  
   (yin yang))

(define (id x) x)
(define (f x) (display "O")  x)
(define (g x) (display "-")  x)

((f (call/cc id)) (g (call/cc id)))

meetlai

书后标的是原价

以下4折：

「·已出·」深入理解计算机系统 (第一版) http://book.douban.com/subject/1230413/ 定价: 85.00元
「·已出·」实用Common Lisp编程 (伞哥翻译的,全新，书的封膜还没撕） http://book.douban.com/subject/6859720/ 定价: 89.00元 
「·已出·」编程的本质 : 英文版 http://book.douban.com/subject/4722718/ 定价: 49.00元
「·已出·」汇编语言(王爽) http://book.douban.com/subject/3037562/ 定价: 33.00元
「·已出·」卓有成效的程序员(影印版） http://book.douban.com/subject/3558788/ 定价: 45.00元
「·已出·」ML程序设计教程 http://book.douban.com/subject/1316040/ 定价: 45.00元

meetlai

data Color = R | B | M | F deriving (Show, Ord, Eq, Read)

cards = concat $ zipWith (zip.repeat) [R,B,M,F] ["4AQ", "23478J", "456QK", "5A"]
only f cs cp = filter (\x -> filter (f x ==) (map f cs) `cp` [f x]) cs

p1 = only snd cards (/=)
q1 = filter many cards where
    many(c,n) = all number (filter ((==c).fst) cards)
    number(c,n) = filter ((==n).snd) cards /= [(c,n)]
p2 = only snd q1 (==)

meetlai

import Control.Monad
import Control.Concurrent

chans = sequence $ replicate 100001 newEmptyMVar

whisper chans = do
  forM_ (zip chans (tail chans)) $ \(left,right) -> forkIO $ do
    msg <- readMVar right
    putMVar left (msg + 1)
  forkIO $ putMVar (last chans) 1