About adding new script language

Hi GDB folks!
I'm new comer here, and I'm trying to make guile the extension language.
Anyway, folks could use python as well, before guile has reliable python
front-end.
I've read the python part, here're some ideas, correct me if I'm wrong
please. ;-)

1. Is it necessary to use language_defn to define the extension
language?
My understanding is language_defn defines a new language support for
debugging the defined language, not to define a new extension language
for other debugging purpose. Or not?
For example, go-lang.c is the support for debugging go, not add go as
the debug script language, just like python. But it confused me that
python has used language_defn.

2. There should be interfaces to add the script language, but I didn't
find it, anyone point me out? I don't think I have to write new
lexer/parser for that, just need a way to get the expr and call guile's
read function. Thanks!

3. My aim is not only add guile as an extension in gdb's REPL, but a
more powerful language for the automatic debugging. For that purpose,
the hard/heavy work is not to add guile into gdb, but a framework
project implemented by guile based on the support of guile-gdb. 
Is this idea too unrealistic?

Happy hacking!
Thanks!

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