计算小写和大写，然后将其作为元组返回

Question

I want to implement a function called countLowerUpper which takes a String and count lower and uppercases and return it as a tuple. For example : countLowerUpper "TeST" should return (1,3) . I don't know how to return a tuple properly. I am forced to use countLowerUpper :: String-> (Int,Int) . I can't change it.

import Data.Char
countLowerUpper :: String-> (Int,Int)
countLowerUpper = (length . filter (isLower),length . filter(isUpper))

EDIT After received help I change my code to:

import Data.Char

countLowerUpper :: String-> (Int,Int)
countLowerUpper str  = (lowerCount,upperCount)
    where lowerCount =length . filter(isLower)
          upperCount =length . filter(isUpper)

But still have got error:

 error:
    • Couldn't match expected type ‘Int’
                  with actual type ‘[Char] -> Int’
    • Probable cause: ‘upperCount’ is applied to too few arguments
      In the expression: upperCount
      In the expression: (lowerCount, upperCount)
      In an equation for ‘countLowerUpper’:
          countLowerUpper str
            = (lowerCount, upperCount)
            where
                lowerCount = length . filter (isLower)
                upperCount = length . filter (isUpper)
  |
4 | countLowerUpper str  = (lowerCount,upperCount)   | 

I know that isLower don't have got any argument but I don't know what to use. Maybe str? Or use head and tail of string?

Answer 1

import Data.Char

countLowerUpper :: String -> (Int,Int)
countLowerUpper str = (lowerCount,upperCount)
    where lowerCount = undefined
          upperCount = undefined

You can do this.