Bluish Coder

Here are a bunch of blogs from my RSS reader that I think are worth reading. Some of them haven't updated in a while, but the archives may be worth a look anyway.

* Blogs with a math focus:

http://blog.sigfpe.com

http://bit-player.org

http://mathr.co.uk/blog/

https://www.johndcook.com/blog/

* Blogs with a programming languages focus:

https://existentialtype.wordpress.com

https://bluishcoder.co.nz

http://blog.ezyang.com

http://akkartik.name

http://lambda-the-ultimate.org

http://mrale.ph

* Blogs with a UI design focus:

http://www.brandonwalkin.com/blog/

http://ignorethecode.net/blog/

http://interuserface.net

* Blogs with a graphics / 3D rendering focus:

http://c0de517e.blogspot.com

http://diaryofagraphicsprogrammer.blogspot.com

https://directtovideo.wordpress.com

http://graphicrants.blogspot.com

http://www.reedbeta.com

http://www.realtimerendering.com/blog/

https://blog.demofox.org

http://eelpi.gotdns.org/blog.wiki.html

* Other interesting / more general programming blogs (many of these have a "systems" focus):

http://danluu.com

http://ewontfix.com

http://chneukirchen.org/blog/

http://neverworkintheory.org

http://apenwarr.ca/log/

https://www.snellman.net/blog/

https://www.pvk.ca

http://psy-lob-saw.blogspot.com

https://randomascii.wordpress.com

http://fastcompression.blogspot.com

https://fgiesen.wordpress.com

http://blog.plover.com

http://chneukirchen.org/trivium/

http://rachelbythebay.com/w/

You are doing yourself a great service by learning Scheme - that can fundamentally change how you think about programming. Reading the first chapter of SICP[0] will change you forever. Yet right now you're using Scheme as a Python/C/Ruby with a strange syntax, while it's a totally different language with its own idioms. You should learn them to master Scheme.

As for your particular questions:

1. map yields an error under mzscheme

I'm at work, and didn't have access to a proper scheme, so I used an online REPL[1], which apparently is more forgiving. Regardless, you can write your own map (a good exercise!) that stops as soon as one of the arguments is exhausted. Make it tail-recursive[2] as well!

2. list-ref is bad

Lists are beautiful data structures designed for recursive algorithms. If you are using lists and not using recursion (or a hidden recursion in the form of map), you're doing something wrong. list-ref uses list as a vector, which has a performance implications - your algorithm is O(n^3) while mine is O(n^2).

3. set! is bad

Margins are too small for a proper explanation :), but basically set! has side-effects[3], and functional programming should avoid having them.

Have fun learning Scheme!

[0] http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-9.html#%_chap_1
[1] http://www.bluishcoder.co.nz/jsscheme/
[2] http://en.wikipedia.org/wiki/Tail_call
[3] http://en.wikipedia.org/wiki/Side_effect_(computer_science)

I see. Yeah, I stand corrected.

I was conflating continuation-based and closure-based webservers because both allow straight-line code instead of explicitly managing url handlers.

And the traditional rhetoric in favor of this technique has come from Seaside, which popularized the name 'continuation-based' (http://www.linux-mag.com/id/7424; http://www.bluishcoder.co.nz/2006/05/server-side-javascript.html)

I'd never seen anybody say this is just an early-prototyping technique. But searching found Patrick Collison concur: http://www.quora.com/Whats-the-best-continuation-based-web-framework

It was too harsh to say it paints us into a corner; it is possible to replace fnid links with new defops. I went back and looked at the frontpage when not logged-in, and saw that there are 0 fnid links in that common case. (One possible way to gradually use a second server would be to just serve the frontpage off it. You'd need to move to a centralized store for user/profile/story objects, but the fnids table could continue to live on one server.)

It also turns out that there's at least one company trying to scale continuation-based servers (http://bc.tech.coop/blog/040404.html). So it was overly harsh to call it a dead end.

I have written a single javascript program in my life, and it was an emulator for an 8080-based machine. I used https://bluishcoder.co.nz/js8080/ for that part of the emulator, though I had to make some changes to it.

I found the emulator ran 4x faster on firefox than on chrome. The culprit was the main dispatch loop, a 256-entry switch statement. Chrome used a slow fall-back path because there were too many cases. The fix was to have "if (opcode < 128) { switch for first 128 cases} else { switch for other 128 cases }". It made FF a little bit slower, but greatly sped up on Chrome.

I also tried generating 256 functions and then dispatch to the right sub based on an array of function pointers, but it wasn't any faster than the switch statement.

But that was five year ago, and I'm sure the landscape is different now.

I think you can do this with proof assistants, and with the SPARK version of Ada.

You can also do it with a dependent type system. I haven't used it, but from what I've read, in the ATS programming language, which is dependently typed, you can guarantee that array index accesses and pointer arithmetic never goes out of bounds, at the cost of having to pass proof variables explicitly to various functions.

This poster goes over how to ensure you don't cause buffer overflows in it:

https://bluishcoder.co.nz/2014/04/11/preventing-heartbleed-bugs-with-safe-languages.html

https://bluishcoder.co.nz/2018/01/10/capturing-program-invariants-in-ats.html

It's a bit obscure; this is the only person who's ever blogged about ATS, as far as I can tell.

So awesome.

Presumably this doesn't yet allow streaming, including scrubbing / resolution & bitrate switching / etc, since Media Source Extensions / MPEG-DASH aren't supported in anything but Chrome?

MSE: https://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html

MPEG-DASH: http://en.wikipedia.org/wiki/Dynamic_Adaptive_Streaming_over_HTTP

Apparently Firefox is getting close, which is heartening: http://bluishcoder.co.nz/2013/08/20/progress-towards-media-source-extensions-in-firefox.html

If anyone from Kickstarter is here, love to hear if you're starting to play with MSE support for supported browsers, or if you're just doing download-and-play. Congrats either way - so glad to see more of this.