I remember when I was in college, a very tricky quiz was to convert recursive code to a non-recursive one. I have always found it very challenging.

Permutation can easily be solved with recursion. So I tried to solve it without recursion. It was a fun exercise.

alpha = 'xyz'

def main():
    n = list(alpha)
    while n:
        print n
        n = next(n)


def next(str):
    str.pop()
    # loop to find a upgradable tail
    while str:
        tail = str[-1]
        # search for an upgrade to the tail
        new_tail = [i for i in alpha if i > tail and i not in str]
        if not new_tail:
            str.pop()
            continue
        str[-1] = new_tail[0]
        # fill the rest
        return str + [i for i in alpha if i not in str]

If you read the Google Cast API, you know exactly why it is called ChromeCast: the receiver device simply runs a boiled-down version of the Chrome browser and listens for commands sent by sender applications. It seems to also be able to run custom applications as the receiver in the device, as long as it is not resource intensive and it's a regular web application. So the important take-away is that there will be two applications at play, most likely maintained in two separate code bases (not to mention the number of programming languages involved).

Saying there is no SDK for AppleTV is misleading: it's true that there is no way to create custom applications to run on AppleTV (yet), but there is an API to use AirPlay/AppleTV as a second screen. The emphasis is on second screen: there is only one app that simply render content to two screens. The app just sees a second UIWindow instance and renders views on to it as usual, and the system takes care of the rest. It's inherently simple, and there is one codebase and most likely one programming language involved. Apps like Real Racing 2 HD and the Redfin app are taking very good advantage of this well-documented feature. With Mavericks, users can set up an AppleTV as a regular external monitor at the system level, so it's even simpler for developers: if your Mac app can deal with dual monitors, you can utilize AppleTV. Compare this to a Google Cast application: to use the receiver device as a second screen, you either create a dedicated receiver application and get the main app to communicate to it by commands, or you have to roll out your own implementation of a virtual screen: have your UI code draw to a virtual screen, encode the screen pixels as video stream and get receiver to play that stream. The former method is too limited and latter is too cumbersome (and likely infeasible without hardware support).

My reply to the argument that all inventions should be commoditized.

I am all for all inventions must eventually become a commodity. However, if you look at the long term instead of just getting innovation to become cheap commodities available to everybody as soon as possible, some protection should be provided to the inventor so while cool new progressive "stand on the shoulders of giants" changes can keep coming, risky groundbreaking innovations can also emerge once in a while. Without effective patent protection, everybody will resort to do safer small-step improvements instead of spending years and billions to build (and market) something vastly different from what people are familiar with. In other words, with zero patent protection, you will still see cars getting better mileage, but you won't see an electrical car. You will also see more equivalent of pharmaceutical companies becoming more interested in making toothpaste instead of medicine.

If we want to argue for patent reform, we need to focus on the true patent trolls. Apple is not a patent troll and arguing against this will push many people to the other side of patent reform debate.

There is a beautiful story named Jonathan’s Card listed on hacker news today. It is about an experiment on sharing a starbucks card – everybody can buy a coffee on this card, and everybody can also chip in if he wants. It has been interesting to see the balance up and down throughout the day.

Then there is an even more beautiful story on good infection.

My girlfriend and I were graduating from pharmacy school and she was applying for residency positions (yes, they have those for pharmacists). Well, she found out she got the one she really wanted and so that night we went out to a nice dinner to celebrate. We did it up like you would expect a happy couple to – nice bottle of wine, share an appetizer and dessert, etc. We were still living on loans at the time and so in my head I was keeping track of about how much the meal was going to run me at the end of the night (for better or worse – keep in mind we were in college at the time). We had easily cleared a hundred bucks (quite the meal for college students who usually eat $7 sandwiches or more likely cook for themselves!), and when it was time for the bill, our waitress told us “The couple that was sitting over there paid for it.”

And some people pay for bridge toll for more than just themselves.

Google is fighting a six-front war, and some are saying Google is sitting comfortably in their search advertising castle, and playing guerrilla warfare everywhere else. I don’t think so.

Don’t ever think Google is playing guerrilla warfare just to poke fun at the other guys while sitting on a pile of cash. The reason Google is attacking these companies is simple: they have become clear threats to Google’s core business – not search, but targeted advertising on the web. Apple’s race to dominance to the mobile space with its walled-garden approach was threatening the whole web-based and ads-driven model; Microsoft’s stronghold on browser market with an ancient browser was holding the web hostage and killing the potential of web as a service serving platform; Facebook keeps valuable information that is not accessible to Google bot and may even be able to develop the next big thing to replace search, not to mention that it is sucking the best talent; and it has been very clear that local advertising is where the future growth of targeted advertising will be from.

Google is being offensive and aggressive, and they are not comfortable about it when their core business – not search but serving ads – is being threatened.

GitHub released its Mac client. It’s very top notch, and has a very modern feeling. rjh29 on HN wonders why GitHub would create one native app for one platform rather than basing on something like Qt to build a native app that works on as many platforms as possible. And I argue,

The definition of native app has changed. It’s no longer a synonym for compiled binary; or using native widget. It is not as simple as coding your UI in a cross-platform toolkit. In these days, a native app means something that feels like the built-in apps: it’s beyond skinning and appearance and is more about how the app as a whole interacts with the user to get the job done. As the platforms diverge, it’s now really hard – if not impossible – to make a cross-platform native app. Among Performance, Cost, Time, Scope, you can only pick three. GitHub sacrifices the scope.

catch23 else pointed out an interesting story on the use of cross platform widget set,

Reminds me of when Intuit was building out Quicken — most of their versions were built using cross platform tools, but inside the code it became a big mess and most recently they decided to scrap the whole thing and re-write the mac client in native objective-c instead of c++

After many years of pushing the concept of platform independence, we finally come to realize that it is not an excuse for end user independence. We should not favor developer convenience over user experience.

A bit off topic, but you triggered something I’ve been thinking about for a couple of years. That “spark” is fluency.

I swtiched jobs from being a computer programmer to being an ESL teacher in Japan. Japan is somewhat famous for churning out students who know a lot about English, but can’t order a drink at Mac Donald’s. We used to have a name for those kinds of people with regard to programming languages: language laywers. They can answer any question you put to them about a programming language, but couldn’t program to save their life. These people often make it past job interviews easily, but then turn out to be huge disappointments when they actually get down to work. I’ve read a lot about this problem, but the more I look at it, the more I realise that these disabled programmers are just like my students. They have a vocabulary of 5000 words, know every grammar rule in the book but just can’t speak.

My current theory is that programming is quite literally writing. The vast majority of programming is not conceptually difficult (contrary to what a lot of people would have you believe). We only make it difficult because we suck at writing. The vast majority of programmers aren’t fluent, and don’t even have a desire to be fluent. They don’t read other people’s code. They don’t recognise or use idioms. They don’t think in the programming language. Most code sucks because we have the fluency equivalent of 3 year olds trying to write a novel. And so our programs are needlessly complex.

Those programmers with a “spark” are programmers who have an innate talent for the language. Or they are people who have read and read and read code. Or both. We teach programming wrong. We teach it the way Japanese teachers have been teaching English. We teach about programming and expect that students will spontaneously learn to write from this collection of facts.

In language acquisition there is a hypothesis called the “Input Hypothesis”. It states that all language acquisition comes from “comprehensible input”. That is, if you hear or read language that you can understand based on what you already know and from context, you will acquire it. Explanation does not help you acquire language. I believe the same is true of programming. We should be immersing students in good code. We should be burying them in idiom after idiom after idiom, allowing them to acquire the ability to program without explanation.

So let’s read more good code.

via slashdot.

IIRC, Android sort of does what iCloud does, but iCloud is very different and IMHO a much better offering from a developer perspective. According to Apple’s website:

iCloud Storage APIs enable your apps to store documents and key value data in iCloud. iCloud will wirelessly push documents to a user’s device automatically and update the documents when changed on any device — automatically.

iCloud allows an app developer to treat the cloud as a natural extension of the iOS device. In-cloud storage is almost as easy to use as saving data locally, and you get push synchronization for free.

This is similar to Dropbox, but baked right into the system APIs. I don’t think there is anything like this in Android. You of course can hack something using Google Storage API or Amazon S3, but they are very different beasts from iCloud: while iCloud associate the storage with a user, Google and Amazon associate it with an app. That difference has a huge implication. iCloud makes it trivially easy to synchronize data for one app across devices of the same user. To achieve the same thing with Google and Amazon’s offerings, you would have to provide your own code to identify user, isolate data of different users in the cloud, and bring in your own synchronization/push magic. On the other hand, if you want to mine across data of all users – answering questions like the most-bookmarked pages – then you might feel iCloud’s extra layer of abstraction getting into your way.

Ursula is a photographer, and she loves the photo house called Sophia’s. The place is nice and clean, the service is superb, and the price is reasonable. Since Ursula’s free-lance business is doing pretty well, she uses Sophia’s quite often and enjoys 20% discount as part of their VIP program.

It’s Christmas time, and Ursula receives lots of orders to take family portrait in customer’s houses. Running around like crazy to fulfill all the orders, she could no longer visit Sophia’s to pick up the finished prints.

There is this super nice and considerable customer named Claire who offers to pick up the prints on her own from Sophia’s. Ursula loves this idea. However, there is one problem. Sophia’s treats privacy vey seriously. They would not allow anyone to pick up Ursula’s prints without Ursula’s driver license. Ursula obviously cannot give Claire her driver license because, well, there is simply not enough trust in here and asking Claire to later return the driver license is also too much.

Ursula checks with Sophia about this situation, and is happy to find out there is another way to delegate access to her prints. She just needs to follow these procedures.

1. Make sure Claire is registered at Sophia’s. This is to make sure if Claire does something bad, Sophia’s can track her down. This is one-time process.

2. If Claire is indeed on file at Sophia’s, when she is ready to come in and pick up the pictures, she needs to have something called the Access Token. The Access Token basically says the token holder is authorized to access which resource during which time period. In this case, it should say the holder is authorized to pick up Ursula’s prints on her behalf.

3. To get the Access Token, Claire needs a Request Token endorsed by Ursula for exchange. She first calls Sophia’s to get a general Request Token. Based on instructions on the Request Token, Claire asks Ursula to call Sophia’s directly to validate this Request Token. When the validation is successful, Sophia’s asks Ursula to call Claire and tell her the Request Token is now endorsed.

4. With the endorsed Request Token, Claire then calls Sophia’s to exchange it for a long term Access Token.

5. With the Access Token, Claire can visit Sophia’s at any time before the token expires to get the prints as authorized by Ursula.

Many assumes that Facebook has to rely on Google-style in-the-margin ads as its major revenue source. I believe Facebook has the potential to bring a new form of online ads, for example, a new interactive game-like campaign that virally spread across the friend network with those participants given incentives like Facebook credits.

It’s rather limiting to think Facebook as an advertiser like Google. The real potential of Facebook is way beyond this. Facebook is not just connecting people to their friends. It is a middleman – a platform that connects customers to vendors, fans to artists, and gamers to game developers, and there could be much more than these. Think iOS as a platform that connects mobile users and app developers and how it has worked out – and would have worked out even it was a standalone company. Maybe someone will develop an Amway-style direct selling platform on Facebook. Maybe someone could develop a CRM and compete with salesforce.com for SMB. Or maybe a Priceline clone with social features would emerge. And good thing is Facebook does not need to do all these. It just need to inspire a developer community around it and evolve its platform to support new possibilities.

It’s gold rush again, and like last time – it wasn’t the gold miners that get rich; it was the people who sold the miners and other gold rush followers the tools and supplies they needed.

It seems to have become trendy again to hate Apple no matter what, but this is getting ridiculous. Why is it that Apple is expected to be the only platform vendor that has to maintain their own version of the JVM for free? Jobs is quite correct in saying that Java under OS X has long lagged behind the latest official Sun release. I wish it was more common for Apple to leave more components to third parties now that they’ve got more market share. Another example would be graphics drivers, which lag tremendously in both performance and features. I don’t understand why on Earth any Java dev would want to be stuck indefinitely with Apple’s outdated implementation that by definition would never be a major priority rather then get a version from the main organization behind it. For that matter I blame Sun’s longstanding ambivalence toasted FOSS. If we had a fully open GPL edition of the JVM that was best of class like we should have gotten years ago, this never would have been an issue in the first place. It’s yet another tech Sun’s BS has screwed us on, with their insistance to out ZFS under the CDDL rather then Apache/BSD/LGPL being another major example. Anyone still have that old sun strategy wheel, from before ‘acquisition’ became their final exit?