Just to answer one sprcific question here...
>
> Lyon's book explaing what A_GIMME does, but not A_CANT. I checked m_pd.h a
> bit but didn't make much out of it. It is there where the problem lies?
>

A_CANT is used when an object receives a message but the arguments can't be
safely typechecked by Pd - so these messages are refued if sent by the patch,
but friendly C code can call them using a lower-level mechanism.

cheers
Miller