ed is a line editor in the sense that all of it's commands act on a \n delimited line at a time (compare to say sam/acme's commands that act on a selection and treat \n as just any other character, I can't say much about teco).
I completely understand the conflation of cli and "uses a terminal" of course it is the goddamned year our our lord two thousand dickity twenty three after all, can't fight the jargon drift forever; I just think there is still room in the world for a new text editing command language that exists independent of a particular visual representation.
Within reason, yeah. But it's obnoxious to have the ambiguity, and what term do we use now for an editor that you interact with from the shell's command line (eg. sed, I guess?), or principally from its own command line (eg. ed)? While we're at it, if we're coining new terms, ideally we could distinguish those two.
sed in particular is "the streaming editor" but "streaming" isn't the category I'm looking for, which would also include something like nmh for mail (vs the traditional mail client behaving like ed, or things like mutt/pine that run in the terminal but provide more of a GUI that happens to be rendered in text).
“a line editor is a text editor in which each editing command applies to _one_or_more_ complete lines of text designated by the user”
Also, ed commands all can work on multiple lines by prefixing them with an address range. For example,
1,4l
will output the first four lines of the file to the output device.
I also think a defining feature is that line editors don’t automatically show a full screen of the document because they’re designed to be usable on a teletype, where printing a line took about 10 seconds. In fact, even just outputting the current line after each command was considered wasteful.
