What even is "literate programming"? (2024)
31 comments
·December 2, 2025em500
zahlman
> I chose the name WEB partly because it was one of the few three-letter words of English that hadn’t already been applied to computers.
Heh.
rhdunn
In a way this is what notebooks are for Python and other languages. They mix documentation and code such that you can run that code and inspect the output. See for example the pytorch tutorials.
d-lisp
Yes, notebooks are a restrictive type of litterate programming, interactive and browser bound.
TeX was "proven" as a text/typography tool by the fact that the source code written in WEB (interleaving pascal and TeX (this is meta (metacircular))) allows for you to "render" the program as a typographed work explaining how TeX is made+ run the program as a mean to create typographic work.
I'm lacking the words for a better explanation of how do I feel sbout the distinction, but in a sense I would say that notebooks are litterate scrips, while TeX is a litterate program ? (The difference is aesthetical)
d0mine
There is Org Babel in Emacs that can be an alternative to jupyter notebooks for literate programming (research/devopsy tasks). It is more powerful in some aspects and weaker in others.
electroglyph
or all the unsloth notebooks
d-lisp
I dream of a world where the Knuth idea of programming and mathematics are naturally embedded in our cultures, like novels are.
I find it weird to not be able to find linux source code and commentaries or even math/physics/science masterpieces in libraries where you can find Finnegan's Wake easily (at least where do I live), and not be able to talk about the GHC in between two discussion about romance or the weather at the bakery.
Nevermark
> I find it weird to not be able to find linux source code and commentaries
That one statement is a great concise explanation/motivation for "literate programming".
Explanations with code, that explain code design choices, in a way that enables the code to be understood better, and the ideas involved to be picked up and applied flexibly to reading and writing other code.
Another way to view it is: Developers are "compilers" from ideas to source. Documenting the ideas along with the "generated" source, is being "open source" about the origin and specific implementation of the source.
forgotpwd16
An interesting project I stumbled upon recently is AirLoom[0], essentially a reverse literate programming tool. Rather having code and prose interweaved (either Knuth-style code-within-prose or doc-style/as-comments prose-within-code), you've them split in dedicated in segment-annotated code and prose referencing those segments. AirLoom can then produce a combined document with references replaced by the actual code segments. This allows using a normal programming environment (not possible in first approach) and being order independent (not possible in second approach).
elviejo
There is also verso / recto that uses the same technique.
https://github.com/nickpascucci/verso
I actually wish for a tool that would use two things: 1) navigate code like a file system: Class/function/lines [3..5]
2)allow us to use git commit revisions so that we could comment on the evolution of the code
So far the only thing capable has been leoEditor + org-babel
PhilipRoman
Thanks for mentioning this. I built the same thing a year ago for myself in dozen lines of AWK. Looks like great minds think alike :)
In my opinion this is the most practical approach for real world projects. You get benefits like avoiding outdated documentation without huge upfront costs.
dandersch
Couple things that helped me understand literate programming:
- A literate program has code and documentation interleaved in one file.
- Weaving means extracting documentation and turning it into e.g. a pdf.
- Tangling means extracting code in a form that is understandable to a compiler.
A crucial thing to actually make this paradigm useful is the ability to change around the order of your code snippets, i.e. not letting the compiler dictate order. This enables you to code top-down/bottom-up how ever you see fit, like the article mentioned. My guess on why people soured on literate programming is that their first introduction involved using tools that didn't have this ability (e.g. jupyter notebooks). Also, you usually lose a lot of IDE features: no go-to-definition, bad auto-complete, etc.
IMO, the best tool that qualifies for proper literate programming is probably org-mode with org-babel. It's programming language agnostic, supports syntax highlighting and noWEB for changing around order. Of course it requires getting into the Emacs ecosystem, so it's destined to stay obscure.
svilen_dobrev
>> A literate program has code and documentation interleaved in one file.
>> - Weaving means extracting documentation and turning it into e.g. a pdf.
>> - Tangling means extracting code in a form that is understandable to a compiler.
Interesting. i have made a few times DomainSpecific-"languages" - like for chips-module-testing , or for HR-payroll stuff - expressed in some general language with an engine underneath, which allowed for both turning/rendering the DS-"code" into various machine-readable outputs - verilog, labview, .. - as well as various documentation formats. Essentially a self-contained code-piece-with-execution/s-and-documentation/s, with the feature to "explain" what goes on, change-by-change.
Never knew it might be called literate programming.
ChrisMarshallNY
I’d guess that tools like Doxygen and Apple docc are probably the most obvious examples of documentation extraction.
I’ve written code for many years, with Doxygen/Jazzy/docc in mind (still do[0]). I feel that it’s a big help.
cjfd
Documentation like doxygens is almost completely opposite from literate programming. The comment you are responding to emphasizes the ability to determine yourself the order in which to present the documentation. Literate programming is writing a document in the first place where, as an afterthought, a program can be extracted. Source code with doxygen is source code where, as an afterthought, documention can be extracted from. In many cases doxygen documention is quite worthless. Very often it is very helpfully documented that the method get_height, "gets the height". It is very fragmentary documentation where the big picture is completely missing. There is also a case where doxygen-like documentation is needed. This is when writing a library that is going to be used by many people. But then the doxygen comments should only be used on methods that you want those other people to use. And then there is still the danger that there will be too little higher level documentation because the doxygen is treated like it is sufficient.
Literate programming is, in my opinion, only used very seldomly because keeping an accurate big picture view of a program up to date is a lot of work. It fits with a waterfall development process where everything that the program is supposed to do is known beforehand. It fits well with education. I think it is no coincidence that it was brought to prominence by D.E. Knuth who is also very famous as an educator.
ChrisMarshallNY
OK. Fair enough, but remember that Doxygen also analyzes code structure, and can generate things like UML diagrams, and inheritance trees.
Maybe a tool like Rational Rose is more along those lines.
I’ve always been a proponent of writing code in a manner that affords analysis, later. That’s usually more than just adding headerdoc.
rgreeko42
Isn't Org Mode and your LISP of choice the ideal literate programming environment? I'm surprised REPL-based LISP isn't mentioned at all.
stingraycharles
To me the definition of literate programming is much less interesting than the spirit: for complicated logic / parts of code, I try to take the reader through the whole top-down plan / approach, as if it’s a story I’m writing to my colleagues about what’s going on and why. In those parts of code I can easily have 10 times as much lines of comments than code, but it’s important to use it sparingly: people tend to start to ignore comments if they’re low value. But it’s much more effective to have good comments than external documentation, as external documentation has a tendency to go out sync with the code.
As with most things, don’t be dogmatic.
toolslive
> As with most things, don’t be dogmatic.
It depends. If you want to learn faster, you should be dogmatic: "In der Beschränkung zeigt sich erst der Meister." If you want to become a better programmer, please do set extra challenges (fe pure lazy functional progamming only, pure literate programming, ...)
stingraycharles
That’s true, I was mostly referring to it in a professional setting, not for educational purposes.
nerdypepper
relatedly, i have been using literate haskell to document my advent of code journey this year:
- day 5's solution for example: https://aoc.oppi.li/2.3-day-5.html#day-5
- literate haskell source: https://tangled.org/oppi.li/aoc/blob/main/src/2025/05.lhs
the book/site is "weaved" with pandoc, the code is "tangled" with a custom markdown "unlit" program that is passed to GHC.
svilen_dobrev
well, maybe it is everything that is not "illiterate programming", i.e. "programming-without-understanding".. which decade by decade gets more and more abundant/dominating.
i do similar thing which i call live-sketching.. a mostly-no-content python namespace-hierarchy of module(s) and classes (used as just namespace holders), and then add (would-do-somehing) "terminal" methods, and combine-those-into-flows actual "procedures" methods , here and there .. until the "communication" diagram starts appear out of it, and week after week, fill the missing parts. It feels like some way of writing executable spec over imagined/fake stuff, and slowly replacing the fakes with reals. Some parts never get filled. Others are replaced with big-external-pieces - as-long-as matching the spec needed. What's left is written by hand.. and all this maybe multiple cycles.
This approach allows for both keeping the knowledge of what the system should do - on the spec / hierarchical level - and freedom to leave things undone, plug some external monster, or do-it-yourself as one sees fit. The downside is that the plumbing between pieces might be bigger/messier than the pieces - if you have ever seen the spiderweb of wires above a breadboard with TTL ICs..
e.g. for my Last project - re-engineering a multiple-aging-variants of kiosk-system into coherent single codebase that can spawn each/most of the previous - took me 6 months to turn a zoo of 20x 25KLoc into single 20Kloc +- 5 for the specializations - and the code-structure still preserves the initial split-of-concerns (some call it architecture), and comms "diagram", who talks to who when/why.
But yeah, it's not for faint-hearted, and there little visibility of the amount of work going/done, as the structure at day 1 is more or less the structure at day 181, and management may decide to see only that..
zkmon
You are beating around a bush of nothing.
machino
I’ve inherited some CWEB code from a colleague. My interpretation is that you write it like stream of consciousness, interleaving thinking and chucks of code. Not all code your write ends up in the final C file.
However, the final effect is spaghetti code (you can surrogate “goto” by injecting code in different locations.) And docs are hard to read.
But, it really forces you to explain what you do and how you got there, which is incredibly useful for reconstructing history. (Theirs is also a sort of diff file for it, I think with .ch extension, to amend files.)
loa_in_
The examples are definitely acknowledgement worthy.
I imagine the biggest hurdle on the path towards adopting this is writing down clear, readable prose using highly technical language. And naming things. Using ambiguous human language to describe a complex algorithm without causing a conflict in a big team.
js8
Maybe I am weird, but I would like to see/program in a formal, yet fuzzy/modal language, which could serve as a metalanguage that describes (documents) the program. This metalanguage must have some kind of constructs to describe unknown things, or things that are deliberately simplified in favor of exposition. So basically eschew natural language completely in favor of fully formalized description, that could be manipulated programmatically.
However, I don't know what this metalanguage should be. I don't know how to translate typical comments (or a literate program) into some sort of formal language. I think we have a gap in philosophy (epistemology).
svilen_dobrev
search for "Controlled natural language". Many attempts in the past - ~20y ago, one of these is even called "Attempto", near nothing recently. Seems not enough interest in wide audiences
npodbielski
Maybe it will be unpopular opinion but if your idea has to be explained after 50 years in a blog post maybe it was not that good after all. Or maybe idea was good but state of the tools and culture of your field is not best place to implement it, like the blog post ask: what tool you would use for literate programming? Or you need to write a tool for literate programming first? For me it sounds bit like runnable python notebook, which is great for DevOps stuff but not really for developing financial system. And I do not want to start about lack of tests as author states.
This essay seems to be missing the main primary references for literate programming:
https://www.cs.tufts.edu/~nr/cs257/archive/literate-programm...
https://www-cs-faculty.stanford.edu/~knuth/lp.html
Knuths intention seems clear enough in his own writing:
Literate programming is a methodology that combines a programming language with a documentation language, thereby making programs more robust, more portable, more easily maintained, and arguably more fun to write than programs that are written only in a high-level language. The main idea is to treat a program as a piece of literature, addressed to human beings rather than to a computer.
and
Let us change our traditional attitude to the construction of programs: Instead of imagining that our main task is to instruct a computer what to do, let us concentrate rather on explaining to human beings what we want a computer to do.