At this point, you know about the two necessary steps to initialize
Clon: defining a synopsis and creating a context. If you paid
attention to the quick start application (see Quick Start), you may
have noticed that defsynopsis was called as a top-level form
whereas make-context was called from the function main. So
why the difference?
First, I hope that you see why a context cannot be created as a toplevel form. If you do that, you will end-up creating a context relevant to the Lisp environment from which the application is created, not run.
The synopsis, on the other hand, could be defined either as a toplevel
form, as done in the quick start and the demo programs, or in the
function main, just before making a context. There is a very good
reason to prefer a toplevel form however: that reason is called
“integrity checks”.
When you define a synopsis (or any synopsis item, for that matter),
Clon performs a number of checks to make sure that you’re making a
sensible use of the library. In fact, the number of semantic mistakes
that you can make is quite puzzling. You could for instance define
several options with identical names, forget to provide a fallback or
default value when it is required, provide invalid fallback or default
values, and the list goes on and on. These are just a few examples but
there are many more, and Clon checks all of those (I think).
Since those mistakes relate to the definition of the application itself,
they do not depend on a particular execution of it. Consequently, the
sooner Clon catches them, the better. If you define your
application’s synopsis as a toplevel form, Clon will be able to
perform its integrity checks when the application is created, not only
when it is used. In other words, you won’t be able to get a working
application until your use of Clon is semantically correct.
This is why it is strongly recommended to create synopsis from toplevel
forms, and this also explains why Clon chooses not to provide
an initialize function that would wrap around defsynopsis
and make-context together.