Why do we need modules at all? (2011)
81 comments
·April 2, 2025rdtsc
hinkley
Software development is continually emotionally stunted by a lack of people with expertise in multiple other fields.
English absolutely has namespaces. Every in-group has shibboleths and/or jargon, words that mark membership in the group that have connotations beyond the many dictionary definitions of that word (in fact I wonder how many words with more than three definitions started out as jargon/slang words that achieved general acceptance).
You cannot correctly parse a sentence without the context in which it was written. It’s a literary device some authors use. By letting the reader assume one interpretation of a prophetic sentence early on, the surprise the reader experiences when they discover a different interpretation at the end intensifies the effect.
mechanicalpulse
I'm reminded of a Final Jeopardy! clue from a few years back --
> As of 2013, this 3-letter verb common in sports, theater & politics has the largest entry in the online OED.
The correct response? What is "run"?
0perator
It's arguable that any group's dialect is actually a fork of English specialized for a specific culture, activity, or context. Occasionally, elements of the fork are pulled into upstream English as groups grow in popularity and jargon or shibboleths become more commonly used across dialects.
rdtsc
> Software development is continually emotionally stunted by a lack of people with expertise in multiple other fields.
I think Joe's point is about the perennial discussion whether hierarchy is better than tags. It's as old as software or as old as people started categorizing things. Some early databases were hierarchical KV stores. Email clients and services go through that too, is it better to group messages by tags or have a single hierarchy of folders?
> English absolutely has namespaces
Sure, we can pick apart the analogy, after all we're not programing in English unless we write LLM prompts (or COBOL /s). Then if English has namespaces what would you pick lager.flat.alcoholic or alcoholic.lager.flat or lager.alcoholic.flat, etc? Is there a top-level "lager" vs "ale" package, with a flat vs carbonated as next level?
d0mine
"whether hierarchy is better than tags" sounds like whether hammer is better than a screwdriver. Use a tool appropriate for the job.
Hierarchy seems more rigid less general than tags but when it works--it works.
froh
yes. and math/logics trained brains confuse hierarchical namespaces with trees. names in nested namespaces should be DAGs, maybe even arbitrary graphs, meaning a chair can be a sit-on thing in several contexts, but not in all (think meeting).
in many contemporary programming languages you can express this, too, by exporting some imported name.
twic
> The dot in the name has no semantics it's just a separator.
That's not true of all module systems. It's true in Java, but not in Rust, where it establishes a parent-child relationship, and in which context [1]:
> If an item is private, it may be accessed by the current module and its descendants.
[1] https://doc.rust-lang.org/reference/visibility-and-privacy.h...
kibwen
And privacy in Rust is load-bearing for encapsulating unsafe operations from safe code, so it's not just a nice-to-have, its fundamental to the language.
null
auggierose
but we do have alcoholic beer, and non-alcoholic beer, and it is nice to be able to say which one you want. And yes, there is a separator here, too, it is called a space.
ludston
We need modules so that my search results aren't cluttered with contamination from code that is optimised to be found rather than designed to solve my specific problem.
We need then so that we can find all functions that are core to a given purpose, and have been written with consideration of their performance and a unified purpose rather than also finding a grab bag of everybody's crappy utilities that weren't designed to scale for my use case.
We need them so that people don't have to have 80 character long function names prefixed with Hungarian notation for every distinct domain that shares the same words with different meanings.
sweezyjeezy
I agree, but also agree with the author's statement "It's very difficult to decide which module to put an individual function in".
Quite often coders optimise for searchability, so like there will be a constants file, a dataclasses file, a "reader"s file, a "writer"s file etc etc. This is great if you are trying to hunt down a single module or line of code quickly. But it can become absolute misery to actually read the 'flow' of the codebase, because every file has a million dependencies, and the logic jumps in and out of each file for a few lines at a time. I'm a big fan of the "proximity principle" [1] for this reason - don't divide code to optimise 'searchability', put things together that actually depend on each other, as they will also need to be read / modified together.
feoren
> It's very difficult to decide which module to put an individual function in
It's difficult because it is a core part of software engineering; part of the fundamental value that software developers are being paid for. Just like a major part of a journalist's job is to first understand a story and then lay it out clearly in text for their readers, a major part of a software developer's job is to first understand their domain and then organize it clearly in code for other software developers (including themselves). So the act of deciding which modules different functions go in is the act of software development. Therefore, these people:
> Quite often coders optimise for searchability, so like there will be a constants file, a dataclasses file, a "reader"s file, a "writer"s file etc etc.
Those people are shirking their duty. I disdain those people. Some of us software developers actually take our jobs seriously.
hansvm
One thing I experimented with was writing a tag-based filesystem for that sort of thing. Imagine, e.g., using an entity component system and being able to choose a view that does a refactor across all entities or one that hones in on some cohesive slice of functionality.
In practice, it wound up not quite being worth it (the concept requires the same file to "exist" in multiple locations for that idea to work with all your other tools in a way that actually exploits tags, but then when you reference a given file (e.g., to import it) that needs to be some sort of canonical name in the TFS so that on `cd`-esque operations you can reference the "right" one -- doable, but not agnostic of the file format, which is the point where I saw this causing more problems than it was solving).
I still think there's something there though, especially if the editing environment, programming language, and/or representation of the programming language could be brought on board (e.g., for any concrete language with a good LSP, you can re-write important statements dynamically).
hansvm
Oops: important -> import
ludston
Indeed! The traditional name for the proximity principle is called "cohesion"[1].
[1] https://en.wikipedia.org/wiki/Cohesion_(computer_science)
6figurelenins
Not to pick on Rails, sorting files into "models / views / controllers" seems to be our first instinct. My pantry is organized that way: baking stuff goes here, oils go there, etc.
A directory hierarchy feels more pleasant when it maps to features, instead. Less clutter.
Most programmers do not care about OO design, but "connascence" has some persuasive arguments.
https://randycoulman.com/blog/2013/08/27/connascence/
https://practicingruby.com/articles/connascence
> Knowing the various kinds of connascence gives us a metric for determining the characteristics and severity of the coupling in our systems. The idea is simple: The more remote the connection between two clusters of code, the weaker the connascence between them should be.
> Good design principles encourages us to move from tight coupling to looser coupling where possible. But connascence allows us to be much more specific about what kinds of problems we’re dealing with, which makes it easier to reason about the types of refactorings that can be used to weaken the connascence between components.
taeric
We could get that without a hierarchical categorization of code, though?
Makes me wonder what it would look like if you gave "topics" to code as you wrote it. Where would you put some topics? And how many would you have that are part of several topics?
hombre_fatal
There is a similar question about message board systems.
Instead of posting a topic in a subforum, what if subforums were turned into tags and you just post your topic globally with those tags. Now you can have a unified UI that shows all topics, and people can filter by tag.
I experimented with this with a /topics page that implemented such a UI. What I found was that it becomes one big soup that lacks the visceral structure that I quickly found to be valuable once it was missing.
There is some value to "Okay, I clicked into the WebDesign subforum and I know the norms here and the people who regularly post here. If I post a topic, I know who is likely to reply. I've learned the kind of topics that people like to discuss here which is a little different than this other microclimate in the RubyOnRails subforum. I know the topics that already exist in this subforum and I have a feel for it because it's separate from the top-level firehose of discussion."
I think something similar happens with modules and grouping like-things into the same file. Microclimates and micronorms emerge that are often useful for wrapping your brain around a subsystem, contributing to it, and extending it. Even if the norms and character change between files and modules, it's useful that there are norms and character when it comes to understanding what the local objective is and how it's trying to solve it.
Like a subforum, you also get to break down the project management side of things into manageable chunks without everything always existing at a top organizational level.
efitz
I agree, but go farther:
Most things have multiple kinds of interesting properties. And in general, the more complex the thing, the more interesting properties it has. Ofc "interesting" is relative to the user/observer.
The problem with hierarchical taxonomies, and with taxonomies in general, is that they try to categorize things by a single property. Not only that, the selection of the property to classify against, is relevant to the person who made the selection, but it might not be relevant, or at least the most relevant, property for others who need to categorize the same set of things.
Sometimes people discover "new" properties of things, such as when a new tool or technique for examining the things, comes into existence. And new reasons for classifying come into existence all the time. So a hierarchical taxonomy begins to become less relevant, as soon as it is invented.
Sometimes one wants to invent a new thing and needs to integrate it into an existing taxonomy. But they have a new value for the property that the taxonomy uses for classification. Think back to SNMP and MIBs and OIDs. Now the original classifier is a gatekeeper and you're at their mercy to make space for your thing in the taxonomy.
In my experience, the best way to classify things, ESPECIALLY man-made things, is to allow them to be freely tagged with zero or more tags (or if you're a stickler, one or more tags). And don't exert control over the tags, or exert as little control as you can get away with. This allows multiple organic taxonomies to be applied to the same set of things, and adapts well to supporting new use cases or not-previously-considered use cases.
taeric
Yeah, I suspect this is one where the general hierarchy does lift quite heavily. Such that it isn't that I would want to lose it, entirely. More that I think it is best seen as a view of the system. Not a defining fact of it.
Is a lot like genres for music and such. In broad strokes, they work really well. If taken as a requirement, though, they start to be too restrictive.
skydhash
Tags are great only when hierarchical structures becomes cumbersome. And even then, there's some limit to how much tags you can have before they become useless.
bob1029
I feel like you are arguing more for namespaces than modules.
Having a hierarchical naming system that spans everything makes it largely irrelevant how the functions themselves are physically organized. This also provides a pattern for disambiguating similar products by way of prefixing the real world FQDNs of each enterprise.
adrian_b
As another poster already said, providing namespaces is just one of the functions of modules, the other being encapsulation, i.e. the interface of a module typically exports only a small subset of the internal symbols, the rest being protected from external accesses.
While a function may have local variables that are protected from external accesses, a module can export not only multiple functions, but any other kinds of symbols, e.g. data types or templates, while also being able to keep private any kind of symbol.
In languages like C, which have separate compilation, but without modules, you can partition code in files, then choose for each symbol whether to be public or not, but with modules you can handle groups of related symbols simultaneously, in a simpler way, which also documents the structure of the program.
Moreover, with a well-implemented module system, compilation can be much faster than when using inefficient tricks for specifying the interfaces, like header file textual inclusion.
ludston
It is irrelevant until you have 4gb of binaries loaded from 50 repositories and then you are trying to find the definition of some cursed function that isn't defined in the same spot as everything it is related to, and now you have to download/search through all 50 repositories because any one of them could have it. (True story)
layer8
Modules don’t imply namespaces. You can run into the same problem with modules. For example, C libraries don’t implicitly have namespaces. And the problem can be easily solved by the repository maintaining a function index, without having to change anything about the modules.
norman784
Don't forget about encapsulation, there's most likely a lot of functions that aren't relevant outside the module.
AtlasBarfed
The article references the true granularity issue (actually the function names need a version number as well, not sure in my scan of the article if it was mentioned).
Modules being collections of types and functions obviously increases coarseness. I'm not a fan of most import mechanisms because it leaves versioning and namespace versioning (if it has namespaces at all...) out, to be picked up poorly by build systems and dependency graph resolvers and that crap.
poincaredisk
How do you imagine importing modules by version in the code? Something like "import requests version 2.0.3"? This sounds awful when you accidentally import the same module in two different versions and chaos ensures.
_factor
Import latest where signed by a trusted authority.
Gurkenglas
just deduce the domain from text similarity :o)
GrantMoyer
I think Hoogle[1] is proof this concept could work. Haskell has modules, of course, but even if it didn't, Hoogle would keep it still pretty usuable.
The import piece here which is mentioned but not very emphasized in TFA is that Hoogle lets you search by meta data instead of just by name. If a function takes the type I have, and transforms it to the type I want, and the docs say it does what I want, I don't really care what module or package it's from. In fact, that's often how I use Hoogle, finding the function I need across all Stack packages.
That said, while I think it could work, I'm not convinced it'd have any benefit over the statys quo in practice.
kibwen
Hoogle works because of how richly-typed Haskell is, but Erlang is dynamically-typed.
jonnycat
This is one of those things where I don’t agree with the argument, but know the person making it knows way more than I do on the subject and has given it way more thought. In these cases it’s usually best to sit back and listen a bit...
neongreen
> database of functions
This is exactly what Unison (https://www.unison-lang.org/) does. It’s kinda neat. Renaming identifiers is free. Uh… probably something else is neat (I haven’t used Unison irl)
brabel
A lot of things are neat because of this. Refactoring becomes trivial and safe. If you do not change the type of the refactored function, you can safely do a batch replace and everywhere the old function was used, the new one will be used after that. If you do change the type, the compiler interface will guide you through an interactive flow where you have to handle the change everywhere the function was being used. You can stop in the middle and continue later... and once you're done you just commit and push... all the while the code continues to work. Even cooler, perhaps: no unit test is re-run if not affected. And given the compiler knows the full AST of everything , it knows exactly when a test must run again.
jweir
I tried it out. Fascinating language and a completely different paradigm. The language itself is familiar, but the structure of the program is different - no files – all functions are in a database and their history. I found the language a bit difficult to navigate, but that is probably because of my experience of work with files, and having tools based on files.
anonzzzies
Makes me think of Unison [0]. I never used it but I found it interesting to read about.
aeonik
The Bruijn language is a really cool language that takes some of theae ideas to the extreme and fundamentals.
Variables aren't named, they are beta reduced and referred to by abstraction level.
bradrn
Also Io, to some extent: https://iolanguage.org/guide/guide.html#Importing
VMG
Functions are not isolated values.
They are nodes in a graph, where the other nodes are the input types, output types and other functions.
It makes sense to cluster closely associated notes, hence Modules.
Etheryte
As with other similar proposals, doesn't this simply move the complexity around without changing anything else? Now instead of looking for the right module or whatnot, you'll be sifting through billions of function definitions, trying to find the very specific one that does what you need, buried between countless almost but not quite similar functions.
jasode
If there are no modules but a "flat" global namespace which requires every function name to be unique to avoid collisions... it means people would inevitably re-invent pseudo/fake "modules" and hierarchy in metadata tags in large non-trivial codebases.
Consider a function name: log()
Is it a function to log an event for audit history?
Or is it a function to get the mathematical natural logarithm of a number?
The global namespace forces the functions to be named differently (maybe use underscore '_') in "audit_log()" and the other "math_log()". With modules, the names would isolated be colons "::" or a period '.' : Audit.log() and Math.log(). Audit and Math are isolated namespaces. You still have potential global namespace collisions but it happens at the higher level of module names instead of the leaf function names. Coordinating the naming at the level of modules to avoid conflicts is much less frequent and more manageable.
Same issue in os file systems with proposing no folders/directories and only a flat global namespace with metadata tags. The filenames themselves would have embedded substrings with underscores to recreate fake folder names. People would reinvent hierarchy in tag names with concatenated substrings like "tag:docs_taxes_archive" to recreate pseudo folders/directories of "/docs/taxes/archive". Yes, some users could deliberately avoid hiearchies and only name tags as 1-level such as "docs", "taxes", "archive" ... but that creates new organizational problems because some have "work docs" vs "personal docs" ... which gravitates towards a hierarchical organization again.
john2x
This is what Emacs Lisp has, and what indeed does happen with libraries
_Wintermute
Happens with R as well where everything gets dumped into a global namespace. It's a huge mess.
If you're lucky all functions will have a common prefix str_* or fct_*. If you're unlucky then you have to figure out which package has clobbered a standard library function, or the exact ordering of your package import statements you need for your code to run.
bfung
Same with S3 object names.
There’s no directories in S3, just object names.
The feature of the object names being hierarchical with “/“ delimiters are out of habit and easier to reason about for the avg user.
skydhash
Same thing happens to me with Bear.app (note taking). It only has tags, and the first thing I believe everyone does is to go with hierarchical structure again, because you need some tag, but also an additional specifier. Which help with grouping an location (And Bear.app have support for that naming scheme and displays it as a tree).
bionhoward
IMHO, aren’t modules necessary for big projects to limit the amount of complexity we have to deal with at any one time?
Our minds can (allegedly) only handle 7+/-2 concepts in working memory at once. Your whole codebase has way more than that, right? But one module could easily fit in that range.
codethief
> all functions go into a global (searchable) Key-value database
Very much related: https://scrapscript.org/
bjourne
This is an all-time classic, but, sadly, most HN commenters just don't "get it". Perhaps because they have no experience with the Erlang VM so they don't understand Joe's premises The Erlang VM is best described as a dynamic process manager and a "function" is just a callstack template. You want to fix a bug in your executing function without stopping it? Sure, no problem. Just reload the function and have the VM seamlessly upgrade the callstack to the new template. Since data is immutable it mostly just works. Now since functions forms the basic unit of work in Erlang modules are kind of irrelevant. Recompiling a module is the same as recompiling every function in the module. Hence, what use does the abstraction serve? The proliferation of "utils" or "misc" modules in not only Erlang but many other languages supports his point.
Btw, the more experienced I've gotten the more I've found that organizing code is mostly pointless. A 5000-line source file (e.g., module) isn't necessarily worse than five 1000-line files.
skydhash
It's all related to naming. You can refer to a symbol with auth/guard/token/authenticate or auth_guard_token_authenticate, and what matters is the amount of characters you type sometimes. Also you can have encapsulation with the first option.
Smalltalk have the same live experience, but do have modules, because it makes editing easier and encapsulation is nice for readability and clarity.
igouy
Is a 5,000-line function worse than 500 10-line functions?
(Locality of reference.)
I miss Joe, he left us too early. He always had wild ideas like that. For a while he had this idea of a git + bittorrent he called it gittorrent, only to find out someone had already used the name. I think it was a bit of an extension of this universal functions idea.
If you expand some of the comments below, he and other members of the community at the time have a nice discussion about hierarchical namespace.
I particularly like his "flat beer and chips" comment:
https://groups.google.com/g/erlang-programming/c/LKLesmrss2k
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> I'd like to know if there will be hierarchial modules in Erlang, because tree of packages is a rather good idea:
No it's not - this has been the subject of long and heated discussion and is why packages are NOT in Erlang - many people - myself included - dislike the idea of hierarchical namespaces. The dot in the name has no semantics it's just a separator. The name could equally well be encoders.mpg.erlyvideo or mpg.applications.erlvideo.encoder - there is no logical way to organise the package name and it does not scale -
erlyvideo.mpegts.encoder erlyvideo.rtp.encoder
But plain module namespace is also ok. It would be impossible for me to work with 30K LOC with plain function namespace.
The English language has a flat namespace.
I'd like a drink.alcoholic.beer with my food.unhealthy.hamburger and my food.unhealthy.national.french.fries
I have no problem with flat beer and chips.
/Joe
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