9. Lexical scanning (includes also string search and data compression)
10. Parsing techniques
...
And after Volumes 1--5 are done, God willing, I plan to publish Volume 6 (the theory of context-free languages) and Volume 7 (Compiler techniques), but only if the things I want to say about those topics are still relevant and still haven't been said."
Does that mean TeX and ACP delayed the revelation of thoughts about compiler technics by 40 years and he thinks his original thoughts to start the whole thing with are still relevant and at least partially not published/discovered?
Given what he did for computer algorithms (and doc type setting) this makes me really curious about his views on compilers.
He's been publishing in the space all the while [1], I'm guessing a lot of what he still has unpublished is in terms of how to present and connect across the ever growing literature.
Iirc that should be part of the taocp plan.