CODEWITHSUNDEEP
haskell
user3389445
user3389445

Reputation:

Function that counts numbers with multiple digits in Haskell

I'm trying to write a function that counts all numbers from a String in Haskell that have more than 1 digit.

Example 1: "Test1 Test12"

This should return 1 because only "Test12" has more than 1 digit.

Example 2: "Test1 Test12 Test123"

This should return 2 because only "Test12" and "Test123" have more than 1 digit.

This is how my code currently looks like:

import Data.Char
import Data.List
import Data.Function

digits = any ((1<) . length) . groupBy ((&&) `on` isDigit)

count :: String -> Int 
count n = length (filter digits n)

Can anyone help me here?

Upvotes: 1

Views: 906

Answers (1)

bheklilr
bheklilr

Reputation: 54058

Your problem can be broken down into

  • I want to count the number of words in a string that have more than one digit
  • I want to find the words in a string that have more than one digit
  • I want to determine if a word has more than one digit
  • I want to count the number of digits in a word

So the most basic thing that you want to do is count the number of digits in a word. Since a word is a string, that can be easily done by

count :: String -> Int
count word = length $ filter isDigit n

Then you want to determine if a word has more than one digit, which means it should return a Bool:

hasManyDigits :: String -> Bool
hasManyDigits word = count word > 1

Then you want to find the number of words in a sentence with many digits:

wordsWithManyDigits :: String -> [String]
wordsWithManyDigits sentence = filter hasManyDigits $ words sentence

Then you want to count them

countWordsWithManyDigits :: String -> Int
countWordsWithManyDigits sentence = length $ wordsWithManyDigits sentence

The words function splits a string on spaces, and the Data.Char.isDigit function I think is pretty self-explanatory.

You could could combine these into a single function as

count :: String -> Int
count = length . filter ((> 1) . length . filter isDigit) . words

But I think that makes it lose its readability, even though it displays Haskell's ability to compose functions quite well.

Upvotes: 1

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