This module provides a type-based system for providing translations for text strings.

It is similar in purpose to gettext or Java message bundles.

The core idea is to create simple data type where each constructor represents a phrase, sentence, paragraph, etc. For example:

data AppMessages = Hello | Goodbye

The RenderMessage class is used to retrieve the appropriate translation for a message value:

class RenderMessage master message where
  renderMessage :: master  -- ^ type that specifies which set of translations to use
                -> [Lang]  -- ^ acceptable languages in descending order of preference
                -> message -- ^ message to translate
                -> Text

Defining the translation type and providing the RenderMessage instance in Haskell is not very translator friendly. Instead, translations are generally provided in external translations files. Then the mkMessage Template Haskell function is used to read the external translation files and automatically create the translation type and the RenderMessage instance.

A full description of using this module to create translations for Hamlet can be found here:

http://www.yesodweb.com/book/internationalization

A full description of using the module to create translations for HSP can be found here:

http://happstack.com/docs/crashcourse/Templates.html#hsp-i18n

You can also adapt those instructions for use with other systems.