beginner IO question, strict evaluation

[jeff...@gmail.com]

I start this question by framing my bigger problem.

I have several text files, each one representing text for a different language.

lang_en.txt, lang_es.txt, lang_fr.txt, lang_pt.txt, etc.

Each file is a list of key value pairs separated by a tab.

The files contain display strings for a GUI and are thus fairly small files.

I wish to read all the files into memory and close all the handles.

I suppose technically I could leave the file handles open as there are currently just 6 language files.

However, this just seems wrong to me, and I would really like to close the files and still have the data.

This is what I have tried

module Main

(main)

where

import System.IO

strictList (x:xs) = x `seq` x : strictList xs

strictList [] = []

main = do

    h <- openFile "lang_en.txt" ReadMode

    hSetBuffering h LineBuffering

    content <- hGetContents h

    let all_lines = strictList $ lines content

    hClose h

    putStrLn $ unlines all_lines

The above prints nothing.

Moving the hClose to the bottom will print the file contents.

So `seq` doesn't seem to be working.

I am using GHC version 7.6.3.

There is also a second part of this puzzle that I don't know how to do.

I desire to have something like

data LanguageKey = En | Es deriving (Ord, Eq)

data DisplayKey = Red | Green | Blue deriving (Ord, Eq)

en = Data.Map.fromList [(Red, "red"), (Green, "green"), (Blue, "blue")]

es = Data.Map.fromList [(Red, "rojo"), (Green, "verde"), (Blue, "azul")]

languages = Data.Map.fromList [(En, en), (Es, es)]

{- |get display string given a languageKey and a displayKey -}

get :: LanguageKey -> DisplayKey -> Maybe [Char]

get languageKey key = find $ Data.Map.lookup languageKey languages

  where

    find (Just map) = Data.Map.lookup key map

> get Es Red

Just "rojo"

The problem with this version of "get" is that the user will be able to change the language via a GUI.

Thus the languageKey will change at runtime.

I would like to avoid needing to pass languageKey into a very large number of functions.

And finally, I just thought of a third problem.

I know that lookup will always succeed in retrieving a value.  A failure would indicate a bug in the text files.

Is there any way to have "get" return a String instead of Maybe String?