He's thinking about *something*

i didn't expected that from her.
Is she in compiler building stuff or just lexical analysis now?
I mean it's not the case frustrated women do not do a lexical analysis pretty often & also wrong.

if not known already:
i can recommend the "Dragon Books" from O'Reilly, these are two separate books with the same Title:
https://images-eu.ssl-images-amazon.com/images/I/51FWXX9KWVL._AC_UL600_SR600,600_.jpg
and https://docstore.mik.ua/orelly/bookshelfs.html
Some Knowledge never get's old.

and if you wanna go to the practical part:
https://gigamonkeys.com/book/
Many compilers are built by using common LISP, because it is like LISP were made for this purpose.
The Dragon Books also often refer to LISP.
I made good Experiences with the clisp Package, iirc it was the Interpreter which also was able to create a free running natively executionable binary and the ability to create C Code out of the LISP code.