Re: [web-devel] [Yesod] rendering different templates for different languages

My reasoning for typeclasses is this: Keep in mind this is just a mental exercise, not saying that this would compile... Suppose for your example we wanted to translate it into french: -- Nouns for languages have some way to decide gender, if that matters for the given language class Translate a where toPlural :: Noun a -> Int -> [Words a] data French = French { ... stuff ... languageCode = "FR" } instance Translate French where toPlural = frenchPluralizationEngine

From there we go with something like your .trans files: we give each language the extension according to their language code. So basket.fr is the french translation:

Vous avez #{toPlural 'chien' (maleDogs myBasket)} et #{femaleCats 'chatte' myBasket)} dans votre charrette. This would be pluralized by chien being run through a pluralization engine if necessary I know my thinking is rough so far since you've obviously given it a lot of thought, but does my concept make sense? -- Ian Duncan On Monday, February 21, 2011 at 1:20 AM, Michael Snoyman wrote:

Let's look at a more concrete example: you have an online store selling male dogs and female cats. So you would have:

data Basket = Basket { maleDogs :: Int, femaleCats :: Int }

What you need is a function such as:

renderBasket :: Basket -> String

for each language. In English, this could be something like:

pluralize :: Int -> (String, String) -> String pluralize 1 (x, _) = x pluralize _ (_, x) = x

renderBasket (Basket dogs cats) = concat [ "You have decided to purchase " , show dogs , pluralize dogs ("dog", "dogs") , " and " , show cats , pluralize cats ("cat", "cats") ]

In Hebrew, some words (like years) have a singular, plural *and* dual form, so pluralize for Hebrew may look like:

pluralize :: Int -> (String, Maybe String, String) -> String pluralize 1 (x, _, _) = x ++ " אחד" -- in Hebrew, the "one" comes after the word, all other numbers before pluralize 2 (_, Just x, _) = x -- for dual form, you never show the number, it is assumed pluralize i (_, _, x) = show i ++ " " ++ x -- for the plural, put the number before

If we could build up a library in Haskell of such helper functions, I think it would make translating applications much simpler. But this is the point where we would need a lot of collaboration: I can help out on English and Hebrew (and if I still remember it, Spanish), but I don't know a thing about Japanese, Russian, or most other languages in the world.

I'm not sure how much it would really help to use typeclasses here, however. I think for the most part it will just be an issue of having a separate module for each language. What I'd *really* like to figure out is how to make a nice, easy-to-use wrapper around all of this for translators, who will likely not know any Haskell. Perhaps a language similar to Hamlet:

# strings-english.trans Hello: Hello Person name age: #{name} is #{age} #{pluralize age "year" "years"} old. Basket dogs cats: You have purchased #{dogs} #{pluralize dogs "dog" "dogs"} and #{cats} #{pluralize cats "cat" cats"}.

Michael

On Mon, Feb 21, 2011 at 8:57 AM, Ian Duncan wrote:

...

And of course in some languages such as Japanese, there are barely any gender distinctions or such things as pluralization at all. Perhaps we need pluralization, conjugation, and 'genderization' typeclasses with instances defined for different language datatypes?

-- Ian Duncan

On Monday, February 21, 2011 at 12:46 AM, Michael Snoyman wrote:

The other day I was speaking with a woman on the train. She was telling me about her daughters. I wanted to ask her how old they are, but I got the pluralization wrong and instead of saying "bnot kama" (plural) I said "bat kama," (singular) to which she responded 36.

tl;dr: You can offend people just was well with pluralization issues as with gender issues.

Michael

On Mon, Feb 21, 2011 at 8:40 AM, Max Cantor wrote:

Of course, you just pointed out one of the big difficulties with i18n. I dont think you're wife would take kindly to you referring to her in the male gender. so now, you need the person's gender too. i18n is hard :( the whole would should switch to esperanto.

max

On Feb 21, 2011, at 2:25 PM, Michael Snoyman wrote:

A proper i18n solution is high on my wish list right now, but I've purposely avoided implementing one so far since I'd rather wait until I think we have a good solution as opposed to implementing an acceptable solution now. But let me share my ideas, it might help you out here.

In general, it's very uncommon that you need a completely separate set of templates for each language. Your markup, classes, styles, and logic will likely be identical for each language, and creating a separate template for each will just result in a lot of pain in the long run. Instead, you're likely better off having a single template and just translating strings.

I've blogged about this before[1]. My idea is to use a datatype for your translatable strings, and then have a function that takes a language and a value and returns the translated string. A simple example:

data Strings = Hello | Person String Int toEnglish Hello = "Hello" toEnglish (Person name age) = name ++ " is " ++ show age ++ " years old" -- obviously need to check if person is 1 year old and correct

toHebrew Hello = "שלום" toHebrew (Person name age) = name ++ " הוא בן " ++ show age ++ " שנים"

The nice thing about this approach is you have the full power of Haskell to address typical translation issues, such as pluralization, word order and gender matching. (As a counter example, at work, we use XSLT for this, and then you get the full power of XSLT for solving the problem ::cringe::.)

You can then use the languages[2] function from Yesod to help you out:

getRenderString = chooseFunc `fmap` languages where chooseFunc [] = toEnglish -- default language chooseFunc ("en":_) = toEnglish chooseFunc ("he":_) = toHebrew chooseFunc (_:x) = chooseFunc x

Then you can write a handler function like:

getPersonR name age = do render <- getRenderString defaultLayout [$hamlet| <h1>#{render Hello} <p>#{render $ Person name age} |]

Which will work for English and Hebrew just fine. Ideally, I would like to add support to Hamlet for this directly, involving a String rendering function similar to the URL rendering function already in place. But for the moment, this should work.

I'd love to hear peoples opinions about this.

Michael

[1] http://docs.yesodweb.com/blog/i18n-in-haskell [2] http://hackage.haskell.org/packages/archive/yesod-core/0.7.0.1/doc/html/Yeso...

On Sun, Feb 20, 2011 at 11:19 PM, Dmitry Kurochkin wrote:

Hi all.

I want a handler to render different templates for different languages. I have getCurrentLanguage function and now I try to do something like:

getRootR = do currentLanguage <- getCurrentLanguage defaultLayout $ do addWidget $(widgetFile $ currentLanguage ++ "/homepage")

This results in:

GHC stage restriction: `currentLanguage' is used in a top-level splice or annotation, and must be imported, not defined locally

This makes sense to me, because TH is calculated at compile time. I would like to hear ideas how to work around this restriction. Perhaps there is an existing solution in Yesod?

At the moment, the best I could think of is smth like this:

getRootR = do currentLanguage <- getCurrentLanguage defaultLayout $ do case currentLanguage of "en" -> addWidget $(widgetFile "en/homepage") ... and so on for each language ...

Obviously, this is not a solution taking in account that there are many languages and many handlers.

I was considering creating a global (template file name -> rendered template) map. But I am not sure this is really feasible.

Regards, Dmitry

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