We will need the htx package for XML manipulations and the chunksOf function from the split package, as presented in the following code snippet:

import Text.XML.HXT.Core
import Data.List.Split (chunksOf)

Define and implement main to read the input.html file.

main :: IO ()
main = do
  input <- readFile "input.html"

Feed the HTML data into readString, thereby setting withParseHTML to yes and optionally turning off warnings. Extract all the td tags and obtain the remaining text, as shown in the following code:

  texts <- runX $ readString 
           [withParseHTML yes, withWarnings no] input 
    //> hasName "td"
    //> getText

The data is now usable as a list of strings. It can be converted into a list of lists similar to how CSV was presented in the previous CSV recipe, as shown in the following code:

  let rows = chunksOf 3 texts
  print $ findBiggest rows

By folding through the data, identify the course with the largest capacity using the following code snippet:

findBiggest :: [[String]] -> [String]
findBiggest [] = []
findBiggest items = foldl1 
                    (\a x -> if capacity x > capacity a 
                             then x else a) items

capacity [a,b,c] = toInt c
capacity _ = -1

toInt :: String -> Int
toInt = read

Running the code will display the class with the largest capacity as follows:

$ runhaskell Main.hs

{"PHIL 1000", "9:30", "120"}