“错误 - C 堆栈溢出”在 Haskell 中使用 Hugs

Question

我正在努力将 CSV 文件解析为 CSV 类型，它是一个记录列表，它是一个字段列表，只是字符串。插入新行然后尝试访问 csv 后，出现 c 堆栈溢出错误。我读过这个错误可能来自使用尾递归太大的“thunk”，但我不认为这就是我做错的地方？

type CSV = [Record]
type Record = [Field]
type Field = String

run :: IO()
run =
 do
  inFile <- readFile "myFile.csv"
  let csv = parse inFile
  let csv = (insertRow "abc,def,ghi" csv)
  putStr (show csv)

insertRow :: String -> CSV -> CSV
insertRow newRow csv = csv ++ [toRecord newRow]

parse :: String -> CSV
parse file = map toRecord (parseLines file "" [])

toRecord :: String -> Record
toRecord line = parseWords line "" []

-- parseLine input partialCSV records
parseLines :: String -> String -> [String] -> [String]
parseLines [] partial records = records ++ [partial]
parseLines ('\r':xs) partial records = parseLines xs [] (records ++ [partial])
parseLines (x:xs) partial records = parseLines xs (partial ++ [x]) records

-- parseWords input partialRecord fields
parseWords :: String -> String -> [String] -> [String]
parseWords [] partial fields = fields ++ [partial]
parseWords ('"':xs) partial fields = parseQuotes xs partial fields
parseWords (',':xs) partial fields = parseWords xs [] (fields ++ [partial])
parseWords (x:xs) partial fields = parseWords xs (partial ++ [x]) fields

parseQuotes :: String -> String -> [String] -> [String]
parseQuotes ('"':xs) partial fields = parseWords xs [] (fields ++ [partial])
parseQuotes (x:xs) partial fields = parseQuotes xs (partial ++ [x]) fields

Answer 1

let 绑定是递归的，因此这一行

let csv = (insertRow "abc,def,ghi" csv)

创建了一个无限循环，您以一种不会终止的方式自行定义 csv 。将其更改为

let csv' = ...

并在下一行中打印 csv'。

Answer 2

双 let csv = ... 看起来很可疑。你能尝试解开这两个变量吗？它可能不会做你想要的（在 Haskell 中 let 是递归的）。