Haskell, trying to translate an input word from a given dictionary

Question

Hey I'm just getting started with Haskell and I'm trying to write a programm that translates an input word by reading a .txt file that has some translations in it. Before that I've written a programm that lets a user put in translations.

import System.IO

main :: IO ()
main = do
  putStrLn "Type in an english word"
  d <- getLine
  if null d
      then return ()
      else do
            putStrLn "Type in a german translation"
            b <- getLine
            putStrLn (d ++ " means in german " ++ b)
            appendFile "woerterbuch.txt" (", " ++ d ++ " " ++ b)
            main

So now I've got the file woerterbuch.txt in which I have the english and german words listed like this: Hello Hallo, House Haus, ect. What I'm trying to do now is to get these words into Tuples so I can print the second (german) word if the user types in an english word.

import System.IO

    main :: IO()
    main = do
      putStrLn "Type in an english word"
      d <- getLine
      [contents] <- readFile "woerterbuch.txt"
      if d `elem` [contents]
          then do
            print contents
          else do
                  putStrLn "There's no translation available!"

This is what I've come up with after multiple tries, I understand that elem is for Lists so I need an alternative for my .txt file and then try to put out the second word of the tuple with the snd command. So firstly how can I create the translations input as tuples and secondly how can I test if the asked word is in this list and then print out the second element of the tuple it is part of. Any help would be greatly appreciated.

Ami Tavory Ami Tavory · Accepted Answer · 2017-05-12T17:50:37

I understand that elem is for Lists so I need an alternative

You could use Map.fromList to create a balanced-tree dictionary - Data.Map. Specifically,

import qualified Data.Map as Map 

main = do
    contents <- readFile "woerterbuch.txt"
    let ls = lines contents
    let ws = fmap words ls
    let m = Map.fromList [(t!!0, t!!1) | t <- ws, length t == 2]           
    ...

lets you use m as a dictionary.

Haskell, trying to translate an input word from a given dictionary

1 Answers