Have you ever had a physical notebook, a text file on your computer, or a blog in which you write your thoughts, but where you never look back on what you wrote? Where after you write your thoughts, the next day you just keep on writing more unrelated thoughts without building on the previous days' thoughts? Spaced inbox helps you with that problem by periodically showing you old notes you've written, gently reminding you to build on your previous thoughts.

Spaced inbox implements a minimal writing inbox with support for spaced repetition. How does it work?

1. You write your notes in a plain text file. Two blank lines, or a line containing at least three equals signs (and nothing else) like ======, are interpreted as the beginning of a new note.
2. You create a file called inbox_files.txt (see example) to tell the program where to find your notes file. (The first column of inbox_files.txt is a short name you can give to your inbox file.)
3. You run script.py. This imports your writing inbox into a database that manages the review schedule.
4. Every day, you run script.py, both to import new notes into the database and to review notes that are due. The "review" consists of a single note that is due on that day, along with line numbers that tell you where in the file the note is located. You visit the location using your text editor, edit/delete/do nothing, then tell script.py that you've reviewed the note. This is like pressing "Good" or "Again" in Anki, and will modify the review interval in a spaced manner. You can keep running script.py to get more notes to review, if you feel like it. There is a concept of "dueness" so eventually you will run out of notes to review, but you should not feel obligated to keep reviewing. The spacing algorithm is designed so that even if you stop reviewing for a long time, or you only review a couple notes per day, you will still get the notes that feel most exciting to you (unlike in Anki where the oldest cards dominate the review).

That's it! There's no app or writing interface: you get to choose your favorite text editor, and write in whatever markup language you prefer. script.py does not modify your notes file in any way.

The spacing algorithm that determines which notes are "due" is a simplified version of the one for Anki/SM2 with an initial interval of 50 days, so it goes 50 days, 50*2.5 = 125 days, 125*2.5 = 313 days, and so on. However, among the "due" cards, there is more logic to pick ones that should feel the most exciting to you, rather than randomly picking among them or just showing you the card that is most overdue.

The spaced inbox program in this repo is a research project designed specifically for myself. Eventually I do want to convert it into something that is easy to learn and use, but at the moment this is not the intention. In particular, updates to the code may make the program incompatible with older versions of the database, the interface or spacing algorithm can change at any time, and things are not documented very well in general.

Nonetheless, I do want to help people use the program. So if you are stuck about how to use it or have a question about something, please open a discussion topic (or an issue for bug reports).

(Note as of 2023-01-12: I've significantly changed the note-selection algorithm during reviews, so I think using Anki would give a significantly different and worse-in-my-opinion experience. That's the most important reason to not use Anki, in my opinion. But I'll leave the text below, which were my old reasons for not using Anki.)

There are two senses in which one might "use Anki":

1. Add notes directly to Anki using the Anki interface, and review using Anki: I think it's pretty important to reduce friction for capturing thoughts. So this rules out adding notes directly to Anki for me. I could look into figuring out how to quickly and comfortably add new notes to Anki, but I've been wary of going down the rabbit hole of customizing Anki.
2. Have a plain text file in which to add notes, but periodically collect these notes and add them to Anki using a script, then thereafter review using Anki: I could have done this instead, but (a) I didn't think of doing this when I started, (b) it would have taken longer to implement the inbox, since I would have had to read Anki documentation about its database structure (whereas with my current implementation, I could just roll my own database schema), (c) when it comes time to edit any notes, I would be stuck editing them in the Anki's interface rather than my preferred text editor, and (d) something I like to do is to scroll up in the inbox file to see some of my recent thoughts (especially when picking things to write about on my wiki). I could do this in Anki using the browse window, but I would have to click on each note instead of just scrolling. Again, it's not something that is impossible to do using Anki, but would doing it via Anki would add more friction.

(Thanks to TheCedarPrince for prompting me with the questions that led to these thoughts.)

I'm using gitbash as my terminal, with the graphical Emacs to edit files. I'm sure other setups are also possible but I haven't gotten around to trying them out.

If you wish to run convenience scripts like do.sh, you will need to download sqlite3.exe from this page (it's in sqlite-tools-win32-x86-3350400.zip) and put the executable in your PATH so that gitbash can find it (e.g. place it in C:/Users/YOURNAME/bin).

Once starting Emacs, make sure to run server-start; this allows emacsclient to send elisp code to the existing Emacs instance.

To find the notes that will be due first:

select interval_anchor, interval, date(interval_anchor, '+' || interval || ' day') as due_on from notes where due_on not null order by due_on asc limit 5;

See also the review load visualizer.

• there's a good chance I'll hate how interaction works (right now you have to manually go to the relevant line)

  • There's a way to almost integrate interaction within standard text editors. Vim/emacs already support programs like grep, where it is possible to feed in a list of line numbers and be able to jump between them. This lets you view the notes that are due and navigate between them. However, it does not give you a way to actually interact with that item (i.e. press "good" or "again") -- usually with grep/make you interact by fixing something in the source file itself, and by re-running grep/make, the error clears and it's removed from the list of errors. But with spaced inbox, you don't necessarily want to edit the note at all, in which case, you need some other channel through which to tell the scheduler that you reviewed the note.

    With vim, maybe one possibility is to add commands like :InboxGood and :InboxAgain. Then what happens is that these commands re-import the inbox file (to correct any changes to line numbers), then uses the current line number in the text editor to identify which note the command is about. Then it does an update to the db where the interval/last review date changes. If the note is edited, it's not necessary to press good/again since the review schedule resets to 50 days. Then the command re-runs grepprg/makeprg to refresh the list of due items. (there's actually functions called getqflist and setqflist, which can programmatically alter the quickfix list without setting grepprg/makeprg.)

    Another idea (which doesn't solve the problem above) is for the python script to continuously monitor the inbox text file for changes, and to re-import every time the file is written (at least, while the review session is in progress).

    UPDATE: script.py now supports the --external-program flag, so you can run like ./script --external-program emacs; the cursor in emacs will now jump to the line for the last note that is printed on the command line, so you no longer need to manually type in line numbers with M-g g.

• notes identity is very crude right now: we just check the sha1 hash, so any modification to a note will turn it into a note with different identity, which means the review schedule will reset. I think there's a decent chance this is actually ok: the notes you modify are the notes you are actually engaging with, so you actually want them around more frequently. (Unfortunately, I don't think I will find out if it's fine anytime soon.)

  UPDATE: i think this turned out to work pretty well.

CC0. See LICENSE for details.