Sorting - We're Doing It Wrong

http://blog.rodneyrehm.de/archives/14-Sorting-Were-Doing-It-Wrong.html

by cheeaun • 14 years ago

66 23 14 years ago

blog.rodneyrehm.de

TamDenholm• 14 years ago

This is a very cool visualiser that was posted on HN before if anyone feels like playing: http://visualsort.appspot.com/

y0ghur7_xxx• 14 years ago

previous discussion: http://news.ycombinator.org/item?id=3040157

lliiffee• 14 years ago

Wow-- apparently Mergesort can be implemented in-place!?

Scaevolus• 14 years ago

Yes, but people usually don't since it requires more swap operations and is pretty hard to get correct.

its_so_on• 14 years ago

what, "hard to get correct"? Are we talking about fundamental computer science that literally consists of implementing an algorithm made out of compare and swap/move elements...?

I can't imagine any sort algorithm for which it can possibly be legitimate to say it's 'hard to get correct' unless it's in the sentence 'it's hard for a first-year computer science student to get correct.'

i mean, what is more traditional and basic than implementing tricky sort algorithms?

pestaa• 14 years ago

I had this feeling when we implemented it in school, but couldn't think it through.

My teacher told me it is not possible and convinced me to give up.

brianhempel• 14 years ago

The video is not demonstrating an in-place merge sort. Notice how the sorted pairs suddenly merge. There's another buffer (not included in the visualization) where each merged list is temporarily stored while it is being built up. The sudden merger is when that temporary buffer is copied back into the main list.

gooderlooking• 14 years ago

Maybe I'm the only one who missed the memo, but in case anyone else is wondering what a hash is doing in JS:

"When writing (in text, not in JavaScript) about properties on specific prototypes, you may use the JavaScript notation, foo.prototype.bar. However, this shorter (non-JavaScript) notation is often used instead: foo#bar. Basically, the hash (#) stands for .prototype. — fancy huh?"

http://mathiasbynens.be/notes/javascript-prototype-notation

wahnfrieden• 14 years ago

A bit confusing since it's a common convention to use # to refer to instance members, e.g. Foo#bar means my_instantiation_of_foo.bar

tantalor2• 14 years ago

That's exactly what happens in the JavaScript case:

  new Array().sort === Array.prototype.sort # true

geuis• 14 years ago

You're not alone. I've never seen this before either.

Look, when you're writing an article about programming, stick to spelling things out properly.

It's ok to use acronyms when talking about companies (AT&T, IBM), nations (USA, USSR), or long technical terms as long as you define them early in the document so the reader knows what to expect.

Programming docs should explicitly refer to code in the language being discussed. Array.prototype.sort tells me exactly what you're talking about and my brain doesn't have to make mental leaps to understand what is being said. If its a language I'm not familiar with, like Objective C for example, then I probably will want to copy and search on code being demoed to learn about it. This would be very hard to do if I have to translate your custom abbreviations into the terminology everyone else in the world uses.

Keep it simple and succinct.

crazygringo• 14 years ago

This was confusing for me as well. Why on earth would anyone create a separate "text" notation for a programming language?

Please just stick to writing out ".prototype", if writing for a general audience.

Camillo2• 14 years ago

It's a Ruby-ism.

jdpage• 14 years ago

I've seen it in Javadoc doc comments as well.

tantalor2• 14 years ago

This is fixed in Python:

The sort() method takes optional arguments for controlling the comparisons.

"key" specifies a function of one argument that is used to extract a comparison key from each list element.

In general, the key and reverse conversion processes are much faster than specifying an equivalent cmp function. This is because cmp is called multiple times for each list element while key and reverse touch each element only once.

http://docs.python.org/library/stdtypes.html

numeromancer• 14 years ago

This is worth reading for that video alone. Mergesort was particularly cool.

Rickasaurus• 14 years ago

Another great example of Javascript being awful.

tomjakubowski• 14 years ago

Care to elaborate?

Camillo2• 14 years ago

For a moment, I thought there was actually something new about sorting. That turned out not to be the case, of course.

I understand the importance of linkbait titles, but specifying the context (e.g. "we're doing it wrong in JavaScript") would save people time without weakening the impact on those who might be interested in the article (JavaScript developers).

cldrope• 14 years ago

Thank you. HN seems to be subject to tons of vague or mildly misleading titles and I'm getting pretty sick of it.

I wouldn't be bothered as much, but in some places if you get into too many technical details it seems to confound people and then frustrate them. This is kind of silly since I'm still in college and probably one of the least educated coders here.

Seems wrong to be then downvoted for using basic technical knowledge in a place called Hacker News.

ruxkor• 14 years ago

javascript sorting: having expected a sorting somewhat similar to python and being very... surprised that javascript essentially sorts everything but primitive types by comparing their String counterparts, I decided to implement a more sensible compare function, similar to e.g. python:

https://gist.github.com/2772234

I am currently using this in server only environments, so there is no comparison for DOM elements.

Sorting - We're Doing It Wrong

Related Stories