Ask HN: Particularly elegant programs to study?

[sz]

Examples help tremendously in learning any abstract subject. What are some famously well-written programs whose source is available to look at?

[variety]

The djb way: "straight, no chaser":

   http://cr.yp.to/

qmail in particular, and also (if you like math) primegen.

BTW, his code is not easy to understand (quite the opposite) -- there are few source comments, and most of these are snarky, cryptic or both; and not only does he explain almost nothing on a global scale but oftentimes what he is doing might look, at first blush, kinda wrong, obtuse even.

But that's precisely the point -- there are a lot of idioms in there that most C programmers just wouldn't think of, especially if you're into minimalism (when it comes to things like dealing with strings, error handling, forking, etc).

[kazuya]

> and not only does he explain almost nothing on a global scale but oftentimes what he is doing might look, at first blush, kinda wrong, obtuse even.

Can you give some examples?

[jamii]

I don't know about famous, but Conal Elliots ideas about denotational semantics have led to some beautifully elegant libraries - http://conal.net/blog/posts/denotational-design-with-type-cl...

Don't be put off by the academic tone, at its heart the paper is about how to design abstractions.

[sz]

This looks awesome, thanks. How to design abstractions was what I had in mind when posing the question.

[michael_dorfman]

TeX.

Or, any of Knuth's other Literate Programs.

Also, the book "Beautiful Code" is an attempt along these lines, but personally, I don't find the programs there as beautiful as Knuth's.

[jashmenn]

Léon Bottou's implementation of Stochastic Gradient SVMs is the most concise implementation of an SVM that you'll find: http://leon.bottou.org/projects/sgd

[sz]

(since I had to look it up what a SVM was)

"Support vector machines (SVMs) are a set of related supervised learning methods... The standard SVM takes a set of input data, and predicts, for each given input, which of two possible classes the input is a member of... Intuitively, an SVM model is a representation of the examples as points in space, mapped so that the examples of the separate categories are divided by a clear gap that is as wide as possible. New examples are then mapped into that same space and predicted to belong to a category based on which side of the gap they fall on." [wikipedia]

[d4rt]

sqlite is both beautiful and has a significant test suite. http://www.sqlite.org/

[jamii]

The sqlite test suite is a fantastic example of how to produce solid software. I wish it were used as a case study for all software engineering courses.

[dkurth]

Here's Peter Norvig's toy spelling corrector (in Python), along with some helpful explanation:

http://norvig.com/spell-correct.html

[plinkplonk]

Code from Peter Norvig's "Paradigms of Artificial Intelligence Programming"

[nomurrcy]

Lua (The programming language) is very well written and well worth reading and understanding.

http://www.lua.org/

[davidsiems]

I have to disagree. The language spec and the docs on the Lua website are well written but the VM itself is a mess. It's a trainwreck of ambiguously named variables, minimal documentation, and overuse of macros to force inline code.

The Lua VM is a good example of something that isn't well written from a reading / understanding point of view, but is something that is well written from the 'it works' point of view.

[pygy_]

Here are the source code reading order recommendations by Mike Pall (the author of LuaJIT).

http://www.reddit.com/r/programming/comments/63hth/ask_reddi...

[srean]

I am surprised that nobody has pointed to http://news.usethesource.com/ yet.

[techbio]

I searched for "russian doll pseudocode" hoping to discover something elegant, but the clearest "code" there is a nicely colored Venn-ish diagram.

http://ijcai.org/papers09/Papers/IJCAI09-106.pdf

[petercooper]

This is very Ruby specific (so mostly not "famous" stuff) but if that's your scene, I asked the same question to Rubyists recently and got some good suggestions: http://www.rubyflow.com/items/1817

[jbarham]

http://code.google.com/p/go/source/browse/ is the source for the Go compilers and standard library. Very clean, clear code in the Bell Labs tradition.

[doublez]

The Lift framework core has some rather lithe Scala in it. Do mind that it's an actively developed, actively deployed framework - functionality sometimes takes priority ... ;)

[doublez]

https://github.com/lift/lift

[dawsdesign]

I've heard that Postfix is as close to perfect you can get, but I haven't dived in personally.

[pierrefar]

I've heard good things about the code of Redis and Tokyo Tyrant.

[abyssknight]

c99shell. No, really, it's very well written.