小编Dan*_*nyJ的帖子

不幸的是我无法实现这个功能,我已经尝试了很多.

f5 ::(ab - > c) - >(a - > c,b - > c)

我试过这个

f5 k _ (Left x)     =  k x
f5 _ u (Right y)    =  u y

提前感谢您的帮助.

palindromize :: [a] -> [a]
palindromize [] = []
palindromize [x] = [x]
palindromize (x:xs) = (x:xs) ++ reverse(x:xs)

Run Code Online (Sandbox Code Playgroud)

我在haskell中执行了这个代码但是在中间元素中我不想看到double,怎么做呢？(另一种方式我不想看到原始列表的最后一个元素)我应该使用头部或尾部还是什么？

像那样:palindromize"mad"=="女士"palindromize"race"=="racecar"

我有方向,我就是这样的第1步

这是方向:

 North (x,y) = (x,y+1)
 East (x,y) = (x+1,y)
South (x,y) = (x, y-1)
 West (x,y) = (x-1, y)

怎么实现那样？

   f13 :: [Dir] -> (Int,Int)
    f13 [North, North]                == (0,2)
    f13 [North, East, South, West]    == (0,0)
    f13 (replicate 10 East)           == (10,0)

我的代码:

a = 0
b = 0
f13 :: [Dir] -> (Int,Int)
--f13 xs  = (a,b+1)
f13 xs | xs == North = (a,b+1)
       | xs == East = (a+1,b)
       | xs == South = (a,b-1) …