Developing for the iPhone

The last time I used Objective-C, it wasn't 2.0. As such, I'm needing to brush up quite a bit on my skills. I'm not used to having the compiler generate my properties for me, or the dot syntax etc.

I'm also not a big fan of mixing garbage collection with no garbage collection, I feel that's a recipe for disaster, however I'm going to cautiously proceed anyway.

I will say that the Xcode tools have shown immense improvement since the last release. I wasn't a fan of them at all, and I was surprised that my muscle memory for emacs keybindings isn't wasted completely in the Xcode editor.

If I can keep my interest level high in this area, I may just splurge for that 99 dollar license to deploy applications.

No more Facebook for me.

I decided I didn't want to be a part of their product...

Thoughts on Lazy Evaluation...

... I'll do it later.

Stuff...

So I got an iPad. I've had it about one month. I've been paying a lot of attention to the talk about how it doesn't do Flash, why it doesn't do Flash, how Apple is committing war crimes against humanity by disallowing applications authored in 3rd party tools etc etc.

As a developer who's spent a good bit of time working on different projects that scale from tiny little machines, to medium sized computers to giant supercomputing clusters (yes, I've been on several of the top 10 of the top500 list, writing software to squeeze performance out of them) I can tell you that flexible tool chains, great documentation, and great support do not always go hand in hand.

My opinion on that is that it's a bit sad that I won't be writing and running Haskell code on a non-jailbroken i(Phone|Pod|Pad) but that that's not a deal breaker for most people. Cocoa is a nice framework, with many years behind it making it great. Objective-C is a pretty cool language, (though I feel they should have kept it simpler, no garbage collection, all this automatic atomic update stuff can be confusing etc). Grand Central Dispatch and the libdispatch stuff is powerful, even in a raw C programming context, though some folks I know don't think it's well served to use it outside the realm of Objective-C. Having suffered programming with threads and locks, (even implementing my own locks on certain platforms) I'd say that this is a big step forward in thinking about concurrency and parallelism by means of organizing program code at a low level.

Yes, when you buy Apple's stuff, it's a bit more about doing things "their way" than doing things "your way". The limits Apple places on the hardware it supports with its operating systems, or the limits placed on programmers via the tool chains, are all really there for 2 reasons (in my opinion).

1. It keeps Apple from losing control of its own platform.

2. Apple can focus their engineering and support efforts on making a product that seemingly "just works" with all supported stuff, because the space of stuff to support is a lot smaller!

To me, neither of these things are inherently "evil", as some folks might like to convince you.

I should note I've used my iPad every day since I got it at least one time/day. To pay for it I began selling some of the stuff I intend not to need anymore, such as my old iPod touch, and my old laptop. So far it's been a great trade!

Just a thought or two on strictness

I've noticed that a lot of times when it comes to profiling programs in any language, that it is often surprising where the big cost centers are. Maybe it's just due to experience, but a lot of times I at least feel like I'm not as surprised in imperative languages when I recognize a cost center or my tool chain does. With functional languages, I'm often surprised that certain implementations of functions are as costly as they are, while others are not. This is even more true in "lazy" functional languages like Haskell.

When you're dealing with strict evaluation by default, you can basically just read the program top down and get a good idea for what happens when, and how data much a particular chunk of code ought to be using, and for the most part you'll get this right with experience.

With a language like Haskell, sometimes, all bets are off unless you know very well how a particular library of functionality is implemented. There's both strict and non-strict versions of Control.Monad.State for example. The non-strict version almost requires you to read the code, then think about how much stuff can be deferred to the last minute, and realize that those little deferred computations will have to be evaluated later. This can not only change the order of evaluation and thusly the data size of your program, but can also change the behavior a great deal.

Data.Map has operations within it for update that will be deferred (non-strictly evaluated) and some that are strict. It's important to read the documentation.

My advice to beginners is to try to understand strictness vs non-strictness (often called laziness) in Haskell as early as possible. It will give you great leverage to expressing some really beautiful solutions to problems, and save you from pulling all of your hair out or suffering any existential crises when trying to figure out why a program doesn't do what you thought.

All of that said, it's pretty easy for me to see why some people will decide that non-strict functional programming languages are not for them. It certainly takes a little mind bending to see the value in it if all you've ever done is imperative or strict functional programming, but I promise you the value is truly there. I also find that by challenging myself to learn how to think in these new paradigms I am simultaneously strengthening my understanding of the older paradigms a good deal more, so give it a shot and don't give up! There's help out there for you.

NineP is on hackage!

I'm excited about it. There's still work to be done, but now I think there's a good chance to get a lot more feedback about the module as it's in experimental, and hopefully we can get some of these folks interested in distributed systems to use this nice, simple protocol.

9ph package for cabal/hackage

The 9ph code repository now has a fully cabalized module, and I'm waiting on a response to get permission to upload stuff to Hackage. This will be my first shared contribution to the Haskell community, though all I've done is create a simple test program and some of the administrative work around wrapping this code up. If anyone likes this, the credit should go to Tim.

I've got some ideas for enhancements, and ways to make a nice server/client API on top of this lovely encoding/decoding library that Tim created on top of the very excellent binary package for Haskell and the lovely Applicative module.