lists

’!’ elem phrase

elem ‘p’ “cheese”

functions:

take

drop

elem

zip:将两个列表组合成元组对

length

!!: [1,2,3] !! 0 === 1

reverse

ones

编写一个带有三个参数的函数 subseq：开始位置、结束位置和列表。该函数应返回开始和结束之间的子序列。

subseq :: Int -> Int -> [a] -> [a]
subseq start end xs = take (end - start + 1) (drop start xs)