ファイルを行単位で処理する

以下のようなテキストファイルsample.txtがあるとします。

code:_

Lorem ipsum dolor sit amet, consectetur

adipiscing elit, sed do eiusmod tempor

incididunt ut labore et dolore magna aliqua.

code: (hs)

import System.IO

:t hGetLine

hGetLine :: Handle -> IO String

handle <- openFile "sample.txt" ReadMode

hGetLine handle

"Lorem ipsum dolor sit amet, consectetur"

hGetLine handle

"adipiscing elit, sed do eiusmod tempor"

hGetLine handle

"incididunt ut labore et dolore magna aliqua."

hGetLine handle

*** Exception: sample.txt: hGetLine: end of file

code: (hs)

| countLines :: Handle -> IO ()

| countLines handle = do

| isEOF <- hIsEOF handle

| if isEOF

| then pure ()

| else do

| line <- hGetLine handle

| print (length $ words line)

| countLines handle

| :}

handle <- openFile "sample.txt" ReadMode

countLines handle