package gettext

OCaml-gettext - Internationalization library for OCaml (i18n)

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Internationalization of a program means that the program have the possibility to handle different language. It can output messages which depend on the language of the user. Typically, if a program can output "bonjour" for a french user, and "hello" for an english user, this program is internationalized.

GNU gettext is one of the standard solutions for i18n. You just need to use special functions to translate strings. These functions are used when the program is running to do the translation and when compiling the program to extract the strings automatically. In ocaml-gettext these functions are "s_", "f_","sn_" and "fn_". They are both used to translate at runtime and to extract strings for translation.

ocaml-gettext provides enough service to build a internationalized program. It comes with :

• a pure Ocaml implementation, based on Camomile,
• an alternative implementation with a binding to GNU gettext library,
• ocaml-gettext a tool to extract strings from Ocaml source.

Installation

The recommended way to install ocaml-gettext is via the [opam package manager][opam]:

$ opam install gettext gettext-camomile gettext-stub

Building without Camomile

This project uses standard dune mechanism for building. It provides 3 different packages:

• gettext: the base module
• gettext-camomile; gettext using Camomile.
• gettext-stub: gettext using the C library.

If you want to not use Camomile, you can just compile or test the other module, using dune:

$ dune test --only-packages=gettext,gettext-stub

Documentation

• API documentation is available online.
• Reference manual

Examples

In all the examples, we are using shorthands function s_, sn_, f_ and fn_. It is important to keep this precise names because they are used to extract strings for translation.

This library demonstrates how to define i18n module for a library:

• Define a module LibraryGettext that defines the textdomain and dependencies of the module. In this case mydomain for the textdomain and the only dependencies are Gettext.init.

• In the main library module Library:

  • Use open LibraryGettext.Gettext to give access to all the shorthands.
  • Make an init public, to allow user of the library to initialize i18n for this library. This init will be used as a dependencies for other module.

The GUI example is very similar to the library. The example is library.

This program demonstrates how to define i18n module and a concrete implementation for gettext:

• Define a module ProgramGettext that defines:

  • a textdomain in this case mydomain
  • a list of dependencies in this case ExamplesLibrary.Library.init and ExamplesGUI.Gui.init.
  • a real implementation in this case GettextCamomile.Map.

• In the main module Program:

  • Use open ProgramGettext.Gettext to give access to all the shorthands.
  • Call ProgramGettext.Gettext.init, use Arg.parse with gettext_args returned by this function.

The last pieces needed are the string files. They are traditionally stored in a po directory with a specific Makefile:

• The Makefile contains the most common targets.
• The POTFILES defines which files to look for translatable strings.
• The LINGUAS defines what language file (.po) are present.
• Running make all will generate a .pot file and compile the various language files.

To test the examples:

# Update the PO/POT files.
$> make update-po

# Define location of the .mo files.
$> export OCAML_LOCALEPATH=./_build/share/locale

# Run the default program.
$> dune exec --workspace dune-workspace.dev examples/program/program.exe -- --my-name Chet

Hello world!
Hello world!
There is 1 plate.
There are 2 plates.
There is 1 plate.
There are 2 plates.
Hello Chet

# Run the program for french language.
$> LANGUAGE=fr dune exec --workspace dune-workspace.dev examples/program/program.exe -- --my-name Chet

Bonjour le monde !
Bonjour world !
Il y a 1 assiette.
Il y a 2 assiettes.
Il y a 1 assiette.
Il y a 2 assiettes.
Bonjour Chet