[lelandbatey]

REPL stands for Read–eval–print loop https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93prin...

A REPL, by its name, is a very narrow version of the broader paradigm of interactive computer programming environments. But Notebooks are not REPLs, unless you use REPL to mean "interactive programming environment" and not REPL. Notebooks are much broader than a REPL! In a notebook, you can go back and edit and run individual lines of the notebook without re-running the whole notebook from the start and without re-computing everything that depends on what you just edited. Behavior like this makes it super hard to track the actual state, and super easy to lose track of how things are how they are. That's pretty terrible!

The parent article links this great talk that goes into more detail than the parent post and is much easier to understand: https://www.youtube.com/watch?v=7jiPeIFXb6U

[nikonyrh]

"In a notebook, you can go back and edit and run individual lines of the notebook without re-running the whole notebook from the start and without re-computing everything that depends on what you just edited."

Isn't this a standard on REPLs as well? You can select the code you wish to run, and press Ctrl+Enter or what ever. I must admit, I've programmed Python for about 10 years in Spyder and VS Code now, but I haven't used notebooks at any point. Just either ad-hoc scripts or actual source files.

My definition of a "notebook" is an ad-hoc script, split into individual "cells" which are typically run as a whole. On my workflow, I just select the code I wish to run. Sometimes it is one expression, one line, 100 lines or 1000 lines depending what I've changed on the script.

[lelanthran]

> Isn't this a standard on REPLs as well? You can select the code you wish to run, and press Ctrl+Enter or what ever.

Not usually, no. Type `python` at the command prompt - what you get is a REPL. Type `clisp` at the command prompt, or `wish`, or `psql`, or `perl` or even `bash` - those are al REPLs.

Very different to a program that presents an editor, and then lets the user selectively choose which lines/expressions in that editor to run next. For example, type `emacs somefile.sql` in the command prompt. The application that opens is most definitely not a READ-EVAL-PRINT-LOOP.

[dahart]

Why would adding fancy select or cut-and-paste features to a REPL make it not a REPL? Selectively choosing which lines to run is just a convenience to let you not have to type the whole line or set of lines again, it doesn’t really change the base interaction with the interpreter.

[lelanthran]

> Why would adding fancy select or cut-and-paste features to a REPL make it not a REPL?

For the same reason that adding (working) wings to a car makes it not a car anymore.[1]

I mean, to my mind, when something is satisfying a different primary use-case, then that thing is a different thing.

I'm sure there's some fuzziness in the distinction between "This is a REPL/car and this is a Notebook/plane".

Usually it's very easy to see the distinction - the REPL is waiting for the next command and the next command only while the notebook takes whatever input you give it, determines whether it got a command or content, and reacts appropriately.

[1] Tons of examples, TBH. I don't refer to my computer as my calculator, even though the computer does everything a fancy calculator can do. People don't call motorcycles 'bicycles', even though the motorcycle can go anywhere that a legal bicycle can go. More telling is how people don't call their computer monitor 'TV' and don't call the TV a 'Monitor' even when the same actual item is used for both (i.e. I repurposed an old monitor as a small-screen netflix-box, and now an item that used to be called 'monitor' by wife and kids is called 'TV' by wife and kids).

[fragmede]

a flying car with wings is still a car. that's the whole point of it. it can drive you to the airport and drive like like a car. I don't care what you call your computer, it can still do math. people who have their TV hooked up to their computer would more readily refer to it as a monitor. idk, I just think REPLs are kinda shit for interacting with the present state of a kernel (as Jupyter calls them). Jupyters better, but still kinda shit because it could automatically infer the important variables in scope and keep a watch list like a debugger does. And then suggest things to do with them since it's a repl and not an IDE. but the thing is fundamentally they're Read Edit Print Loop interfaces to the computer and its current working state.

[dahart]

Ugh this is a gish gallop of broken straw man analogies. Being able to select and evaluate a single line in a notebook is nothing like adding wings to a car. Fundamentally, selecting a line to evaluate is no different from typing that line again. It’s a shortcut and nothing more, the interaction is still read-eval-print. Note REPL doesn’t even refer to where the input comes from, the point is simply that it handles your input, processes it, displays the result, and then waits for you for more input. This is as opposed to executing a file where the interpreter exits once the execution is completed, and the return value is not automatically printed.

Jupyter Notebook absolutely is a REPL, see my sibling comment above for the WP link describing it as such. It waits for input, then evals the input, the prints the return value, and then loops.

[dahart]

I’m not sure what distinction you’re trying to make. Maybe you can give some examples of notebooks that are not REPLs, since some of them definitely are. For example, Wikipedia says Jupyter Notebook is a REPL. The bare Python REPL (and the command line REPLs in any language, for that matter) has the exact same issue with tracking state, because what you describe is a problem with all REPLs, and all notebooks that are REPLs. That isn’t generally a serious problem with command line REPLs, because those REPLs aren’t meant or used for large system programming, they’re for trying small experiments. The parent article is pure opinion and seems a bit confused about the idea of using the right tool for the job, because command line REPLs and notebooks both have their place, as do IDE projects with lots of files.

“A Jupyter Notebook application is a browser-based REPL containing an ordered list of input/output cells which can contain code, text (using Github Flavored Markdown), mathematics, plots and rich media.”

https://en.m.wikipedia.org/wiki/Project_Jupyter

[int_19h]

In modern parlance "REPL" means a lot more than that and typically incorporates at least some kind of editable history.