Question

我是Haskell和功能编程的新手。

我的目标是计算文本文档中的段落数量和每个段落中的单词数量。

我尝试通过以下步骤执行此操作：

我将段落转换为一行

type Line      = String
type Paragraph = [String]

parify :: [Line] -> [Paragraph]
parify [] = []
parify ls 
  | null first = parify rest          
  | otherwise  = first : parify rest
  where first = takeWhile (/= "") ls  
    rest  = dropWhile (== "") . drop (length first) $ ls

然后我计算每行中的单词数

lineWordCount :: Line -> Int
lineWordCount = length . words

singleParagraphCount :: Paragraph -> Int
singleParagraphCount = sum . map lineWordCount



wordsPerParagraph :: [String]-> [Int]
wordsPerParagraph = map (singleParagraphCount) . parify . lines

我想要一个这样的结果：

[12, 20, 8]

分别与每个段落中的单词数量相同。

我收到错误

*** Term           : wordsPerParagraph
*** Type           : [Char] -> [Int]
*** Does not match : [String] -> [Int]

Answer 1

您lines :: [Char] -> [String]使wordsPerParagraph成为wordsPerParagraph :: [Char] -> [Int]，但您的签名为[String] -> [Int]

注意，String与[Char]相同。所以也许你写的签名中有一个拼写错误，你想要String -> [Int]而不是[String] -> [Int]

在尝试计算Haskell中每个段落的单词数时出错

1 个答案: