parsing - 使用 Parsec 忽略字母并仅解析数字

Question

此代码仅在"1243\t343\n"存在数字（例如：）时才有效：

tabFile = endBy line eol
line = sepBy cell (many1 tab)
cell = integer
eol = char '\n'

integer = rd <$> many digit
  where rd = read :: String -> Int

有没有办法让它解析"abcd\tefg\n1243\t343\n"以忽略该"abcd\tefg\n"部分？

Answer 1

您可以使用skipMany跳过除数字之外的所有内容。类似下一个：

many (skipMany (noneOf ['0'..'9']) >> digit)

或（取决于您实际需要什么）

skipMany (noneOf ['0'..'9']) >> many digit

Answer 2

所以诀窍是修改整数以简单地跳过字母。

integer :: Parser Int
integer =
  many letter *>
  ((read . concat) <$> many digit `sepBy` many1 letter)
  <* many letter

这可以12a34正确处理。否则像

 many letter *> (read <$> many digit) <* many letter