structures in editors like TECO, QED and E, I’d welcome them as well. The classic is "cookbook for an emacs" but it's from 1980 https://dspace.mit.edu/handle/1721.1/15905 There's also this that's 25 years more recent but 16 years old: https://ecc-comp.blogspot.com/2015/05/a-brief-glance-at-how-5-text-editors.… And this: https://nullprogram.com/blog/2017/09/07/

Not so curious: Keith Bostic was the principal author of both nvi and Berkeley DB.

On Thu, Apr 1, 2021 at 5:26 PM Dave Horsfall <dave(a)horsfall.org> wrote: I'd use SQLite nowadays, because it takes extraordinary care to make sure that no data is lost short of disk failure. It is considerably more robust than the underlying filesystem, and runs embedded in its process. It also means you can readily carry about arbitrary data in additional columns; for example, you could make line marks persistent, including dot. John Cowan http://vrici.lojban.org/~cowan cowan(a)ccil.org Well, I have news for our current leaders and the leaders of tomorrow: the Bill of Rights is not a frivolous luxury, in force only during times of peace and prosperity. We don't just push it to the side when the going gets tough. --Molly Ivins (pbuh)

's' from Webb Miller's _A Software Tools Sampler_ is an exhaustively documented sort-of-stripped-down vi. Admittedly it's a little tricky to get your hands on the source document (I got it from interlibrary loan back at the end of the Before Times, and archive.org lets you check it out for a limited time, but there may be a waitlist). It's interesting in that it's not just studying the source to see how it works, but an actual (large) chapter of a book where he steps through the construction of the individual functions and their keybindings. Adam On Fri, Apr 2, 2021 at 3:42 PM Dave Horsfall <dave(a)horsfall.org> wrote:

This is actually what ed, ex, and vi do as well, albeit not with a standard interface. The buffer is an array of integer offsets into a file. Line n in the buffer is pointed at by buffer[n], whose contents are an offset into the temp file. That offset points to a null terminated line of buffer text. When a new line of text is created (or changed) the new line is appended to the temp file and the corresponding offset goes into the buffer array. One big reason for this was that ed was originally written for a 16 bit machine, and buffers didn't fit in memory. This works very well to insert or delete lines, you only have to copy the line references in the buffer array. It's also convenient for undo, since putting things back just means restoring the original array. My enhanced ed (hed at Wisconsin, Portable ed at Bell Labs) had a second array for undo, and a full copy of the array was made before a change. Bill Joy wrote a fancier implementation in vi, where only lines added or deleted were saved, command-specific. Undo knew which command it had to undo and special-cased each one. The big disadvantage to this structure is that ends of lines are not just newline characters. You can't backspace over a newline, or change newlines to something else.     Mary Ann On 4/1/21 5:56 AM, Tony Finch wrote: