Defensive Programming: Put the Guards Near the Gate

We can file this one under “not interesting to pretty much anyone who reads this blog,” but it’s an important concept for writing robust code. This is part of a discipline called Defensive Programming.

Let’s say you build yourself a castle in a clearing in the woods. There is one path to the front gate, and you need to guard it. “Hah!” you think, “I’ll put the guards where the path comes out of the woods, to stop shenanigans before they even get close!” You post the guards out there in a little guardhouse, secure in the knowledge that no bad guys will reach your gate.

Until someone makes a new path. Perhaps when the new path is created the path-maker will notice that there are guards on the other path and put a little guardhouse on the new path as well. But perhaps not.

In software, it’s the difference between code that says, “when all conditions are right, call function x”, and having function x test to make sure everything is OK before proceeding.

Putting the guard by the trees:

    function x(myParameter) {
        myParameter.doSomething();
    }

    thing = null;

    ... other stuff that might or might not set 'thing'

    if (thing != null) {
        x(thing);
    }

This is fine as long as everything that calls function x knows to check to make sure the parameter is not null first. It might even seem like a good idea because if ‘thing’ is not set you can save the trouble of calling the function at all. But if some other programmer comes along and doesn’t know this rule, she might not do the check.

    // elsewhere in the code...

    anotherThing = null;

    ... other stuff that might or might not set 'anotherThing'

    x(anotherThing); // blammo!

Better to move the guards close to the gate:

    function x(myParameter) {
        if (myParameter != null) {
            myParameter.doSomething();
        }
    }

Now when someone else writes code that calls function x, you can be confident that your guards will catch any trouble. That doesn’t mean you can’t ALSO put guards out by the edge of the forest, but you shouldn’t rely on them.

Pretty Badass…

I just put the following comment in my code:

// now SHIT GETS REAL

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Help Wanted

Anybody know a kickass Web engineer looking for work? I’m happy to discuss specific technologies and whatnot with anyone who might be interested.

Numbers, English, and Lazy Programmers

While doing research for an episode you will likely see shortly, I went to YouTube and did a search. This is what I got back:
Screen Shot 2014-06-11 at 10.46.47 AM
Note that it says I got “About 1 results”. Obviously, “results” is incorrect. There’s only one result! And About? What’s the standard deviation on that result?

This from a company that was bought by Google for a billion dollars or so. You’d think they’d have someone who could spend five frickin’ minutes to put in

if (results.count == 1) {…

and to only include the word “About” when the code rounds off the number of results (which it does for very large result sets). Neither of those things should be difficult, and I’d be embarrassed if my program were so sloppy. Yet there it is on one of YouTube’s most oft-loaded pages.

MapMyRide.com made a bit more of an effort, but didn’t test all the cases:
Screen Shot 2014-06-08 at 5.13.22 PM

11st place! The rule that works for 1 and 21 doesn’t work for 11. Crazy English and the words we have for the low teens. I sent off a friendly report to MayMyRide letting them know; the bug was in a new feature, and MMR doesn’t have the resources that YouTube does. We’ll see if they fix it before I fall to 13rd place.

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Esoteric Programming Languages

Most readers of this blog are probably familiar, at least by name, with some of the more common programming languages out there. This blog is brought to you courtesy of PHP, and then there are the seminal C and FORTRAN (after all these years, still king of the number-crunchers), the infamous COBOL, well-structured PASCAL, ground-breaking SmallTalk, Sun’s heavily-marketed Java and Microsoft’s counterploy C#, and newcomers like Ruby and Javascript.

There are a lot of computer languages. While there are some pretty striking differences between the above, they all have two things in common. They all involve controlling a computer by writing lines of code, and they were all invented to be useful.

There is another category of language that is not burdened by that second attribute. Useful? Pf. Not bound by the constraints of utility, the whole ‘lines of code’ thing often ceases to apply as well. These non-utile outliers fall under the general category of “esoteric language”, sometimes shortened (but not by me) to esolang.

While I have long been peripherally aware of this category of languages, in a small email discussion recently a friend of mine mentioned the language Brainfuck (sometimes written b****fuck to avoid offending people). Another member of the discussion linked to an amusing top-ten list of odd languages. I read the article and my brain started fizzing.

A programming language that is written as a musical score? Blocks of color that simultaneously convey quantity and program flow*? A program specifically designed to be as difficult as possible to write code in?

Some might ask, “why would anyone bother with such useless languages?” I don’t have an answer to that. I could go on about Befunge and the wire-cross theorem, or about Turing Completeness, but at the end of the day, I think it’s the same answer as one might give to the question “why does one bother writing poetry, when prose is so much clearer?”

Some of the languages are just for fun. INTERCAL (Compiler Language with No Pronounceable Acronym) set out with only one goal: to not be like any other language. For instance, since all coders have long been taught to avoid the GO TO command, INTERCAL instead uses COME FROM. And every now and then you have to say PLEASE. You don’t have to be a geek (but it helps) to enjoy this article about INTERCAL and Befunge (includes a Befunge program to generate Mandelbrot sets).

One can only read about esoteric languages for so long before one must scratch the itch and find a new way to write “Hello, World!” on a screen. I became intrigued by Befunge, a language that is not written as lines of code at all, but as a grid that a pointer moves around on, steered by >,<,^, and v characters. The program appealed to me for two key reasons: the characters the program cursor encounters can mean different things depending on which direction the cursor is moving at the time, and, even better, you can have the program alter itself by changing the characters in the playfield. So, here's my Hello, World! in Befunge:


         095*0     v          0*59    <      
This 'Hello World' program is written  in Befunge, a
  language invented expressly to be as difficult to compile
  as possible.
 
 In fact, with this code, control flow  goes straight through
 this block of text and uses the p in  'program' as an instruction.

                                      +
v      g0*59       <                  1
     >                            "H",^
>:0-!|
v    <
     >                            "e",^
>:1-!|
v    <
                 > "0"+292*p >    "l",^
     > :6*9- :9`!|
>:2-!|           > $         ^
v    <
     > 7"0"+273*p                 "o",^
>:4-!|
v    <
     >                            " ",^
>:5-!|
v    <
     >                            "W",^
>:6-!|
v    <
     >                            "r",^
>:8-!|
v    <
       >                          "d",^
>:52*-!|
v      <

      v<
      " 
>:65+-!|
      "
v      <
      ,
      @

Of course, it was absolutely required that the code alter itself at least once, and occasionally have the same symbol mean different things. This program is based on a counter, and when the counter is 0, it outputs an 'H'. When the counter is at 1, out comes an 'e'. 'l' is a little more complicated; after it matches the 2, the program does a little algebra (6x-9) to come up with 3, with which it then overwrites the 2 in the code. That way, on the next loop, when the counter is 3, we get another 'l', and the same equation replaces the 3 with a 9, ready for the 'l' in 'World'.

In the language, ! means 'not'. At the very bottom, this code evaluates the ! as 'not', which causes the program to loop around and pass through "!" (with quotes), turning what had been a program instruction into the exclamation point at the end of "Hello, World!" A nice little exclamation point on my program, as well.

The astute will recognize the place where an error output should occur, but currently doesn't.

You can watch the program execute in Super Slow-Mo with this Javascript Befunge interpreter. Paste the above code into the top box, click 'show', then click 'slow' below. I recommend setting the time to 50ms rather than the default 500.

Wooo! Big fun! While this language is nearly useless for actually accomplishing anything, I like the way you can make your code physically resemble the problem you are solving. A coworker mentioned writing a tic-tac-toe program with Befunge, and I immediately thought of building a program that is a grid of nine segments and the program alters the paths through the grid as moves are made. It would be awesome.

If I went back to college and majored in computer science, I could get credit for writing it.

In my wanderings, there was one program that completely blew my mind. You remember Brainfuck? There are only eight commands in that language, which makes it relatively simple to write an interpreter. An interpreter is a program that reads the code and executes the instructions as it encounters them, translating them from the (allegedly) human-friendly programming language into machine-friendly instructions for that particular processor. (Compilers do all the translating at once, before the program is executed, while interpreters do it on the fly.)

So here, ladies and gentlemen, is a Brainfuck interpreter, written in another esoteric language, Piet:

piet_bfi
(courtesy Danger Mouse — if I'm not mistaken, the inventor of Piet)

That picture right there? That's a program, written in a Turing-complete language, that implements another Turing-complete language. (**)8-O (the sound you heard was my head exploding.)

______

* In Piet, you can write a program to calculate pi that is a circle.

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How to Make a Geek Happy

I once explained in great detail why HTML is the worst thing that ever happened to the Internet. In that episode I was a bit disingenuous — I also snuck in flaws with the protocol that delivers most of that HTML rubbish to your computer: HTTP.

Finally, finally, twenty years later than necessary, the tools are available to make Web applications work like all the other apps on your computer. (If you’re willing to set down your browser, World of Warcraft and its predecessors have been doing this for a long time now. But finally we can have good application design through the browser as well.)

While the primary benefit of this revolution is for the engineers making the apps (whom you as a user have to pay eventually), there are tangible benefits for Joe Websurfer as well. Mainly, things will work better and be snappier. You will curse at your browser about 30% less. (That number brought to you courtesy of the dark place I pulled it from.)

I work in a blissful world where my stuff doesn’t have to work on older browsers, and especially not on Internet Explorer. That means what might be ‘bleeding edge’ for most Web developers is merely ‘leading edge’ for me. I’m starting a new Web application, and it won’t use HTTP. It won’t even use AJAX.

Quick description of HTTP:
Your browser asks the server for something. The server gives it to you, then forgets you ever existed. This is especially crazy when you want your connection to be secure (https), because you have to negotiate encryption keys every damn time. That’s huge overhead when all you want is the user’s middle initial.

And what if something changes on the server that the page showing in the browser should know about? Tough shit, pal. Unless the browser specifically asks for updates, it will never know. Say that item in your shopping cart isn’t available anymore — someone else snapped up the last one. You won’t know your order is obsolete until you hit the ‘check out’ button. The server cannot send messages to the page running in your browser when conditions warrant.

Lots of work has gone into mitigating what a pain in the ass that all is, but the most obvious solution is don’t do it that way. Keep your encrypted connection open, have each side listening for messages from the other, and off you go. The security layer in my new app is so much simpler (and therefore sturdier) that I’m going to save days of development. (Those days saved will go straight to the bottom line at my company, since I’m an operating expense. The effect of my app will also go straight to the bottom line, as I save other people time and energy. Better yet, the people who will be made more efficient are dedicated to making the company more efficient. Those days of development time saved go through three stages of gain. Shareholders, rejoice.)

So, that makes me happy. Web Sockets, event-driven servers, a chance to create the Missing Middleware to make the tools out there fly. Bindings over the wire.

Of course, I’m not building it all from scratch; I’m using and improving tools created by those who have gone before me into this ‘software working right’ revolution. It means picking up a whole toolbox at one time, from database to server to client library to extensions of all of the above. There are times while I’m trying to put it all together that it feels like my head is going to explode. In a good way.

But boy, the difference a good book can make. In technical writing, there are two kinds of documentation: tutorial and reference. Mostly I gravitate toward reference materials: I have a specific question and I want to get a specific answer. References are raw information, organized to allow you to get to the nugget you need. Tutorials are training documents; they take you through a sequence to help you build complete understanding of a system.

There are many technical documents that try to be both, or don’t know which they are. We call those docs “shitty”. Then there are videos. SPARE ME THE FUCKING VIDEOS. Videos as a reference: completely worthless; videos as a tutorial: rarely adequate – what was that again?

(I’d be interested to hear from my formally-trainied tech writer pals about my above assertions.)

Anyway, On the client side I’m using a library called Backbone, and on top of that Marionette. I like them, but I was starting to get lost in the weeds. The reference material is pretty good, but getting an overall understanding of how the pieces worked together was slow and frustrating. Too many new ideas at once.

So I found a book endorsed by The Guy Who Made Marionette (yeah, The Guy. One guy, having a huge impact on the next generation of Internet applications. Could have been anyone, but there had to be The Guy.) that not only puts the pieces together, but introduces best practices and the reasoning behind them along the way. It may well be the best tutorial-style documentation I’ve run across in this industry. So, hats off for Backbone.Marionette.js: A Gentle Introduction. This book really helped me get my ducks in a row. My fastest learning curve since Big Nerd Ranch oh so very long ago.

So all that makes me a pretty happy geek. Lots to learn, Web applications built right, a new project with lots of creative freedom. And while I’m coming up to speed on the new tools, I already see gaps — the tools are young — including a potentially ground-breaking idea, that I will get to explore.

Can you believe they pay me to do this?

Lost in Translation?

Even if you’re not a programmer, take a look at the following lines of code:

public function sendCommunication($oCommunication)
{
    if (self::emailMode != EMAIL_TEST_MODE_NONE) {
        if (self::emailMode == EMAIL_TEST_MODE_LOGGED_IN_ONLY) {
            // DO NOT COMMENT OUT THE FOLLOWING LINES
            // EVER
            // FOR ANY REASON
            // INSTEAD CHECK THE TEST MODE AND SET THE ADDRESS FIELDS ACCORDINGLY
            $oCommunication->to = $oCommunication->from;
            $oCommunication->cc = '';
        }

Now, I ask you, even if you’re not a programmer, you know there’s one thing you would never, ever, do to the above code. Right? Now let’s say you are a programmer, a professional, being paid because of your ability to find solutions to problems and express them in an abstract language.

Now further imagine that changing the above code can lead to the customers of the people paying for this work getting spammed with confusing emails with our client’s name on them.

Yeah, you guessed it.

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