In our work to look into how Python 3 could be implemented for Guile we
have figured out that the only way to make a goops object applicable is to
have it inherit <applicable-struct>. This does not always work the way it
could be expected, for example when inheriting from several classes.
Apparently this works by some flag being set by <applicable-strukt> in
libguile for the object and that flag is checked during application,
calling the 'procedure slot if it's set with some optimization assuming
that 'procedure is the first slot.
Is this correct and if so, is there any particular reasoning behind this
rather than just having all classes that has the slot 'procedure be
applicable?

Yours,
Krister Svanlund