34. Bigloo A practical Scheme compiler User manual for version 4.0a January 2013 -- User Extensions

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User Extensions

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The extension package system allows the language compiled by Bigloo to be extended and this is achieved by associating an extension file with a suffix. The extension file is loaded at the beginning of a compilation and it can do three things: call extern programs (unix programs); define macros; modify the values of some of the compiler's variables (for example, the list of the libraries to be linked with). The Bigloo's initializing procedure is the following:

- If it exists, Bigloo loads the runtime-command file, see Section Compiler Description.
- It then parses the command line to find the source file to compile.
- It extracts the source file suffix and looks it up in its `*auto-mode*` variable.
- If the suffix is found, the associated file is loaded. This file could contain a function named `*extend-entry*` which must accept a list as argument. It is invoked with the Bigloo's unparsed arguments.
- The result of the `*extend-entry*` application has to be a regular list of arguments and these are parsed by Bigloo.

For now, two extension packages exist: the Meroon package which is a native version of the Christian Queinnec object language; the Camloo [SerranoWeis94] package which is a front end compiler for the Caml language [Caml-light]
Furthermore, Bigloo supports the `-extend` option which forces the usage of an extension file. When Bigloo encounters this option, it immediately loads the extension file, invoking the function `*extend-entry*` with the list of arguments which have not been parsed yet.
The extension files are always sought in the directory containing the Bigloo's libraries.

### 34.1 User pass

Bigloo allows the user to add a special pass to the regular compilation, this pass taking place before macro expansion. There are two ways to add a user pass.

- Add a compiled pass: The module `user_user` (in the ``comptime/User/user.scm'' file) is the user entry pass point. To add a compiled pass, put the code of the pass in this directory, import your new modules in `user_user` and modify the `user-walk` function.
- Add an interpreted pass: Set the value of `*user-pass*`, which has to be a unary function, in your `.bigloorc` file and Bigloo will invoke it with the code as argument.

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Last update Thu Jan 24 17:08:36 2013.