Question

I am trying to find the shortest and longest word in a given string. If the entered string is “house tap mobile telephone” then the longest word should be telephone and shortest will be tap. I have already written the following functions. How do i find the index of the strings and find the shortest and longest word out of it?

---------Converting string into a list of strings and finding length of each word--------

stringConvert :: String -> [Int]
stringConvert x = map (length) (words x)

----------Find the longest word-----------

findLongestWord :: String -> Int
findLongestWord x = maximum(stringConvert x)

----------Find the shortest word-----------

findShortestWord :: String -> Int
findShortestWord x = minimum(stringConvert x)

Answer 1

Since you are looking for a certain word, the signatures of your functions should be

findLongestWord :: String -> String
findShortestWord :: String -> String

The stringConvert function you have implemented has the right idea, but it is a bit problematic because the result doesn’t have the information which word is associated with which length. It might be better to separate splitting the string into a word list from the length calculation, and there is a handy function called comparing that actually removes the need for the stringConvert function altogether.

import Data.List (maximumBy)
import Data.Ord (comparing)

findLongestWord :: String -> String
findLongestWord s = maximumBy (comparing length) (words s)

maximumBy is similar to maximum but it takes as the first parameter a function that should be used to compare two items. comparing is a higher-order function that can be used to convert a function of type a -> b (where bis some type that can be compared, i.e. Ord b => a -> b if you are already familiar with type constraints) into a comparison function between two a‘s (i.e. a function of type a -> a -> Ordering).

The shortest word can be found in a similar manner.