I'm very impressed by (and jealous of) anyone who can context switch fast enough to make use of 10 or 15 minutes here and there to do a completely different task (and actually have it be coherent).

I wrote both "Game Programming Patterns" and "Crafting Interpreters" largely in chunks around half an hour between work, parenting, and other life duties. Likewise lots and lots of hobby programming projects.

Context switching is a skill that gets easier the more you practice it, just like any other. There are techniques like leaving good notes to yourself to pick back up where you left off more easily, but a lot of it just mental training. You sort of learn to hold some of the context in your head all the time but keep it idle when you aren't using it.

When I'm hacking on a hobby programming project, I can often fix a bug or tweak a small feature in fifteen minutes, make a commit, and get a little serotonin hit, all while I'm waiting for the wife and kids to get ready to leave the house.

It doesn't always work for all kinds of tasks. Sometimes for more challenging stuff I really do need a larger chunk of time to load it all in my head. But you'd be surprised how easy it is to eat an elephant one tiny bite at a time if you really try.

I had a friend in college who was the ultimate expression of this. If he was in a line, waiting for someone, outside a professor's office hours, etc., he was working on SOMETHING, usually getting ahead of some reading for class. I asked him later, and he gave quite a compelling account of how if you truly added it all up, it had a pretty huge effect in how long it took him to get through his work. He was incredibly bright, went onto a PhD at MIT, and was also very sociable, which I suspect was helped by this strategy of aggressively seizing on these little breaks of time.

I need a good chunk of time to settle into "productive" work, even if it is just reading. I suspect that what is needed is a little bit more discipline at first and slowly it gets easier, but I just never had the ethic to stick to it, and because of this friend I don't even have the ability to claim any doubt as to how impactful it would be.

I got much better at this when my kids were born, because it was the only way I could get work done on some of my (computing) side projects. I went from having hours of uninterrupted "in the zone" time during evenings and weekends to having much less time overall, and what time I did have was broken into smaller chunks.

I got much more thoughtful about how I used my time and also got better at pre-planning what I had to do so as to make the best use of it. Mostly the key was to just try to tackle smaller tasks and accept that progress would be slow.

If you have an activity where you get to _think_ for hours about what you're gonna do, you can really do a lot in 15 minutes.

I feel the same! One bit of advice has helped me take better advantage of those small chunks of time- "Park facing downhill." I don't remember where I first heard it, but the idea is to stop somewhere naturally conducive to resuming work. Start making the list, and stop at a point where it's really easy to write down the next few items. Or leave the really easy bit of code for next time.

I'm not good at it, because I prefer to cross things off when I finish them, but when I can pull it off it saves some of that time getting oriented to what I'm working on.

Yes I also cannot do this. I comfort myself by believing the nature of their work allows them some sort of meditation on what they will do in those little gaps...but they may just have an enviable power that I do not have.

I'm great at this if the other task is routine. For example, if I'm cooking a dish I've made dozens of times, I can context-switch between that and difficult work. If I'm making a recipe I don't know by heart, context-switching to another task ruins my ability to think about either.

I do this. The danger is that switching out is as easy as switching in. What one needs, in addition to the ability to refocus, is some actual discipline.