May 2017

“App: The Human Story” Screening in San Jose

Here’s the scoop. It’s Sunday, June 4 at 5 pm. There’s a panel afterward with a bunch of people from the movie (including me).

You can get tickets. You should get tickets — the event benefits App Camp for Girls.

Plus I think you’ll enjoy it. :)

JSON Feed

I was hesitant, even up to this morning, to publish the JSON Feed spec.

If you read Dave Winer’s Rules for standards-makers, you’ll see that we did a decent job with some of the rules — the spec is written in plain English, for example — but a strict application of the rules would have meant not publishing at all, since “Fewer formats is better.”

I agree completely — but I also believe that developers (particularly Mac and iOS developers, the group I know best) are so loath to work with XML that they won’t even consider building software that needs an XML parser. Which says to me that JSON Feed is needed for the survival of syndication.

I could be wrong, of course. I admit.

Feed Reader Starter Kit

See my RSXML repository for Objective-C code that reads RSS, Atom, and OPML. I’ve done the work for you of supporting those formats. Go write a feed reader! Seriously. Do it.

I planned to have a JSON Feed parser for Swift done for today, but other things got in the way. It’s coming soon. But you probably don’t actually need any sample code, since JSON is so easy to handle.

Feedback so far

Feedback has been interesting so far. Some questions on the GitHub repo need answering.

Some people have said this should have happened ten years ago, and other people have said that they hate how developers jump on the latest fad (JSON).

And some people really like the icon:

Microformats

One of the more serious criticisms was this: why not just support the hAtom microformat instead? Why do another side-file?

My thinking:

My experience as a feed reader author tells me that people screw up XML, badly, all the time — and they do even less well with HTML. So embedding info in HTML is just plain too difficult. In practice it would be even buggier than XML-based feeds.

And there are other advantages to decoupling: a side-file can have 100 entries where there are only 10 on an HTML page, for instance. A side-file can have extra information that you wouldn’t put on an HTML page. And yet, despite the extra information, a side-file can be much smaller than an HTML page, and it can often be easier to cache (since it’s not different based on a logged-in user, for instance).

Microformats sounds elegant, but I don’t prize elegance as much as I value things that work well.

Frontier Diary #8: When Worlds Collide

I spent the weekend making a bunch of progress on the compiler. It has two pieces: a tokenizer, which I created by rewriting the original C code (langscan.c) in Swift, and a parser.

The parser in OrigFrontier was generated by MacYacc, which is similar to Yacc, which is similar to Bison, which is on my Mac. The thing about the parser is that it’s C code, and the rest of the app is Swift.

How do you bridge the two worlds? Easy answer: with Objective-C, which is a superset of C and which plays nicely (enough) with Swift.

So I renamed langparser.y — the rules file that the parser generator uses — to langparser.ym so that Xcode would know to treat the generated parser source as Objective-C. I edited it slightly, not to change the grammar rules but to change how nodes are created (as return values rather than via inout).

I also made my CodeTreeNode class, written in Swift, an Objective-C class so that it would be visible to my Objective-C code.

And then, finally, I started a build…

…and then it stopped with an error because the parser places my CodeTreeNode in a C union, which isn’t allowed in ARC.

Crushed.

* * *

I think I have three options:

  1. Go down the rabbit hole of figuring out how to get the parser to work with ARC.
  2. Go with the flow: have the parser generate nodes that are, as in OrigFrontier, C structs. The last compilation step would be Objective-C code that translates that tree of C structs into a tree of CodeTreeNode objects, and then disposes the C-struct-node-tree.
  3. Write the parser by hand, in Swift.

My thinking:

I could waste a ton of time on #1, and bending tools in that way can be pretty frustrating work when they refuse to bend.

With #2 I’d feel a bit weird about the redundancy: building a tree and then building a copy of that tree with a different type of object.

My heart tells me #3 is the answer. After all, I’ve already done the tokenizer. How hard would it be to parse those tokens into a code tree? I could skip C and Objective-C altogether and stay in Swift. And it would be so fun. (Because that’s precisely the style of weirdo I am.)

* * *

But the real answer is #2. Writing a parser by hand would take way longer than I think. Given enough tests, it shouldn’t be a huge source of bugs, but still.

The thing about #2 is that yes, it’s redundant, it’s doing more work than it needs to, ideally — but my bet is that it would still be so fast that you wouldn’t be able to tell the difference. Computers are so good at this kind of thing. It’s not like reading files or networking; it’s just in-memory traversal and creating/releasing things.

You remember in Indiana Jones that guy with the twirling swords, and Indy gives that look and then just shoots him? The second option is the Indiana Jones solution.

Update 2:05 pm: Two people have already written me to recommend ANTLR. So I will definitely give that a look. It might be exactly what I need.

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