(guile.info.gz) Intro to Modules and Extensions

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(guile.info.gz) Intro to Writing New Modules

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 5.5.3 Intro to Modules and Extensions
 -------------------------------------
 
 In addition to Scheme code you can also put things that are defined in
 C into a module.
 
    You do this by writing a small Scheme file that defines the module.
 That Scheme file in turn invokes `load-extension' to make the features
 defined in C available.  This works since all definitions made by
 `scm_c_define_gsubr' etc. go into the _current module_ and
 `define-module' causes the newly defined module to be current while the
 code that follows it is executed.
 
    Suppose we want to put the Bessel function `j0' from the example
 extension into a module called `(math bessel)'.  We would have to write
 a Scheme file with this contents
 
      (define-module (math bessel))
 
      (export j0)
 
      (load-extension "libguile-bessel" "init_bessel")
 
    This file should of course be saved in the right place for
 autoloading, for example as `/usr/local/share/guile/math/bessel.scm'.
 
    When `init_bessel' is called, the new `(math bessel)' module is the
 current one.  Thus, the call to `scm_c_define_gsubr' will put the new
 definition for `j0' into it, just as we want it.
 
    The definitions made in the C code are not automatically exported
 from a module.  You need to explicitly list the ones you want to export
 in `export' statements or with the `:export' option of `define-module'.
 
    There is also a way to manipulate the module system from C but only
 Scheme files can be autoloaded.  Thus, we recommend that you define
 your modules in Scheme.
 

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(guile.info.gz) Intro to Writing New Modules

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