Writing did get somewhat harder when I transitioned from part 1 (the Java interpreter) to part 2 (the C VM). C is a more finicky language in a lot of ways. Things like the order of declarations matter. So figuring out which order to introduce snippets of code within a single chapter tends to take a little longer, but it's not a big difference.
My rate of progress has generally slowed over the past few years, for a lot of reasons. My initial enthusiasm has naturally waned. There isn't much novelty left in the project for me — writing each chapter is much like writing the previous one. So it's mostly an exercise in discipline now. Meanwhile, of course, I keep stumbling into other new things that I am excited about, so staying focused is hard.
The last few years have also been personally difficult for me in a number of ways. My mother got cancer (in remission now!), two family members died, two friends died, my dog (the one on the back cover of my previous book) was in ill health for a long time and then had to be put down. Lots of other personal stuff like that. 2018 was one of the worst years of my life, even though I'm still very fortunate in many ways.
But through all of that, I've managed to keep going. I work on the book every day, so I worked on it in the hospital waiting room while my mom got a CAT scan. I wrote a measly 59 words the night after we put down my dog. I wrote in the hotel before my friend's memorial service and on an airplane on the way back from my aunt's funeral.
In some ways, the project is a constant comfort in my life, and it's also taught me a lot about the power of perserverance and discipline. I'm really looking forward to it being done and taking a long break. But I'm also looking forward to seeing what I'll be able to do with this discipline next.
It's interesting to hear how you had the code pegged down for this book at the start. The book definitely feels like the result of such considered and planned design. But one of the features I most appreciate in your book are your reflective asides, such as the Design Notes [0]. I also attempt that in my writing, but almost always end up dragging myself down rabbit holes, including rewriting/renaming/restructuring entire code scripts/snippets, if not the project codebases that I've drafted and refer to. Guess I can't delude myself into thinking such bikeshedding is inevitable for this kind of writing!
[0] "Logic versus History" https://craftinginterpreters.com/parsing-expressions.html#de...
"What's in a Name" https://craftinginterpreters.com/introduction.html#design-no...
One of the things I tell myself is that many of these very difficult experiences were also growing ones for me. I, of course, would prefer that the friends and family I lost or who got sick were still here and healthy. But I also have a greater empathy and understanding when I interact with other people going through these same tribulations.
> It's interesting to hear how you had the code pegged down for this book at the start. The book definitely feels like the result of such considered and planned design.
I basically had to write it this way. My previous book was like a recipe book where each chapter is relatively unconnected so I could just start writing. But this book walks through two complete implementations of the same language, which I also designed for the book. So just about any tiny change to anything can affect very distant chapters.
I wasn't even sure if the book would hang together until I designed the language and wrote the code. If I couldn't get to a little toy language I liked or if the implementations had been a sprawling mess, I would have passed on the project. But a couple months in, everything kind of clicked and I realized I basically had to the write the book. It's like the thing was already there and I was just responsible for putting it all down on paper.
> I also attempt that in my writing, but almost always end up dragging myself down rabbit holes, including rewriting/renaming/restructuring entire code scripts/snippets, if not the project codebases that I've drafted and refer to.
I do a lot of that too. Fortunately, having the code pinned down helps. I basically can't touch the code now because doing so would destabilize existing chapters. The fact that I publish incrementally also keeps me from endlessly noodling.
But it is always a struggle to rein myself in and stay focused on making forward progress.