( GH deprecation

Info Catalog ( GH ( gh preliminaries
 19.1 Why the GH Interface is Now Deprecated
 Historically, the GH interface was the product of a practical problem
 and a neat idea.  The practical problem was that the interface of the
 `scm_' functions with which Guile itself was written (inherited from
 Aubrey Jaffer's SCM) was so closely tied to the (rather arcane) details
 of the internal data representation that it was extremely difficult to
 write a Guile extension using these functions.  The neat idea was to
 define a high level language extension interface in such a way that
 other extension language projects, not just Guile, would be able to
 provide an implementation of that interface; then applications using
 this interface could be compiled with whichever of the various
 available implementations they chose.  So the GH interface was created,
 and advertised both as the recommended interface for application
 developers wishing to use Guile, and as a portable high level interface
 that could theoretically be implemented by other extension language
    Time passed, and various things changed.  Crucially, an enormous
 number of improvements were made to the `scm_' interface that Guile
 itself uses in its implementation, with the result that it is now both
 easy and comfortable to write a Guile extension with this interface.
 At the same time, the contents of the GH interface were somewhat
 neglected by the core Guile developers, such that some key operations
 -- such as smob creation and management -- are simply not possible
 using GH alone.  Finally, the idea of multiple implementations of the
 GH interface did not really crystallize (apart, I believe, from a short
 lived implementation by the MzScheme project).
    For all these reasons, the Guile developers have decided to deprecate
 the GH interface -- which means that support for GH will be completely
 removed after the next few releases -- and to focus only on the `scm_'
 interface, with additions to ensure that it is as easy to use in all
 respects as GH was.
    It remains an open question whether a deep kind of interface
 portability would be useful for extension language-based applications,
 and it may still be an interesting project to attempt to define a
 corresponding GH-like interface, but the Guile developers no longer
 plan to try to do this as part of the core Guile project.
Info Catalog ( GH ( gh preliminaries
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