andrew1

I find the environmental criticisms here bizarre; do the communication mechanisms the rest of us use suddenly have no environmental costs?

In fairness, that sounds apocryphal. If it were really common then there would be no money in doing it because the market would have factored in days before the event the fact that the price were going to fall.

It might be the reason that Apple are infringing on the patent is that they are selling, not just using, a product which contains something which infringes the patent.

Thanks, that's an interesting article.

Do you have a link to what you consider to be a good description/definition/tutorial of "Data Oriented Programming"?

If the two larger circles had that ratio then it would imply that the two circles in the bottom left and bottom right would have the same radius. Which they don't appear to. So the ratio between the two larger circles must be slightly smaller, 1.5ish maybe.

I'm not really sure what you mean. If company X allows customers to pay for goods/services with bitcoins then they would be able to pay the wages of their employees using the bitcoins.

> Can someone else explain, why i'd take time off of work to do this job interview? Why not take a day off and interview with Google/Apple/Microsoft instead?

Surely it depends on the job. Maybe it's paying twice as much as Google/Apple/Microsoft for the same role.

Wouldn't the geometric mean of 1 and 3 be sqrt(3) ?

But that's precisely the point, if they're all "highly logical" then in the island-wtih-3-brown-and-1-green case the person with green eyes can't correctly know their eye colour so can't kill themself. But they are in exactly the same situation as a person with brown eyes in the island-with-four-brown-people case. So if the green eyed person in the first case can't deduce their eye colour, then neither can the brown eyed person in the second case.

If you don't agree, please explain to me what extra piece of information the brown eyed person in the second case has which means he can kill himself on day four. As far as I can see they are both in the situation that they can see three people with brown eyes, and no one has yet killed themselves. What is the extra piece of information that allows the brown eyed person in the second case to deduce that he has brown eyes?

OK, so we agree that if there are X <= 3 people then they're stuck and cannot kill themselves.

You claim that if X = 4 and everyone has brown eyes then on day 4 they will all kill themselves. Suppose I am one of these islanders. I can see three people with brown eyes. On days one, two and three no one kills themselves. On day four I get up and kill myself because I know that I have brown eyes.

Fine, now let's consider the case where there are three people with brown eyes, and one person with green eyes:

As I think we've agreed above, the three people with brown eyes cannot infer that they have brown eyes (i.e. the X < 3 case). So they are not able to kill themselves.

But consider the green eyed person: he can see three people with brown eyes and no one kills themselves on days one, two or three.

He is in exactly the same situation at this point as the brown eyed person we considered in the four-brown-eyed-people case. So at this point, by your logic, he must know that he has brown eyes. Which is a contradiction.

I think you are wrong that induction is not involved in establishing eye colour. (unless you can convince me in the X = 4 case that is :) ).

This isn't a problem I'm unfamiliar with it, a colleague asked me it when I was being interviewed for my current job, and it gets rediscussed periodically. I really do think you're wrong I'm afraid.

Suppose instead of being 900 brown eyed people there are X brown eyed people.

Suppose X is one, then the brown eyed person appears to be stuck, all the blue eyed people are dead so he knows he doesn't have blue eyes, but he can't determine what colour his eyes are (are they brown?, are they green?).

If X is two then we're left with two people after all the blues are dead. Each one can see a brown eyed person, but again, this doesn't help them determine what colour their own eyes are. Again, why can they not be green?

The case for X>2 seems similar to the case for X=2, there's no magical point at which they can suddenly all say 'I don't have green eyes, I must have brown eyes'

With all respect, I think you are underestimating the problem. :)

You originally said that the people with brown eyes would commit suicide after 900 days. Can you explain to me how any of them can know for sure that they don't have green eyes?

> It's only a short reprieve though; because either the browns know that only two colours exist (and so on day 100 immediately know they are brown) or they face the same conundrum as blue, and commit suicide on day 900.

In the case where they aren't told that only two colours exist, why would they kill themselves on day 900? Suppose instead that one of the brown eyed people had green eyes, I don't see how the brown eyed people or green eyed person could deduce the colour of their own eyes.

I wouldn't really agree that it doesn't work out in practice. For the systems that I work on, the concept of privacy is extremely useful, perhaps we're doing things 'the wrong way' to believe that but I don't think that's all that likely.

What would you suggest as a better alternative, outside of a purely functional approach? Just as an example, suppose that Java's LinkedList class didn't have a cached size and that instead it went and iterated its elements to calculate its size each time someone asked for it. I might write a wrapper around LinkedList with two private variables, the LinkedList and an int to cache its size in. Then I would update the int each time an operation was performed on my member list. If I can't make those two members private, how can I ensure that no one accidentally updates the list without updating the size, or vice-versa. It mightn't be an unreasonable mistake for someone to think calling mylist.size = 0 would empty the list. What is the 'safe' way of constructing this concept?

I'd have to politely disagree; if your class has mutable state and you want to maintain some invariant relationships amongst the elements of your class then as far as I can see you really need to be able to specify that some operations can only be performed within the class. If your class is immutable then I'd agree that in most cases privacy offers you few benefits.

I haven't followed the story that well, and only skim read this article, but there was a four-ish hour outage in the morning last week. I think the LSE came up OK for about half an hour but then went down (although it might not have come up at all; I can't remember). It seems unlikely that that was caused by data vendors not reporting end of day close prices correctly.

So they're not falling over themselves to fix a bug which no one has noticed for 10+ years, and which hardly anyone is going to hit in actual use. Maybe they're spending their time fixing problems which are actually affecting developers.

IntelliJ's IDEA IDE has excellent Scala integration in the Community Edition (i.e. the free version).

I've been working with Scala for about two years now and in my experience IDEA has always been ahead of Eclipse for Scala development. That being said I prefer IDEA for writing Java code too so this may just be personal preference.

Nope, you can only apply to one college at either Oxford or Cambridge per year (you can't apply to both universities, which probably makes sense as almost everyone who applied to one would probably apply to the other). There is a clearing system I think where if the college you apply to doesn't want you then other colleges can look at your application and choose to interview you, but I think that's fairly rare.

Indeed, Charles attended Trinity College, Cambridge.

Have you done any research on this?

Assume for a moment that the exam results of students follow a bell shaped curve and that the mean and standard deviation of exam results in the state and private sector are the same, then you would expect the proportion of state school pupils accepted by Oxbridge to be the same as the proportion in the general school system. If instead we assume that the mean in the private sector is higher then you would no longer expect the same proportion to be accepted, and indeed that disproportionately many private sector students would get in.

I'm not saying this is the case (although private school students probably do do better in exams on average), but without knowing anything about the situation how can you accuse them of discrimination? The 'oh, I saw a really good person get turned away' argument is silly. Some colleges only offer a few places for some subjects but are presented with 20+ students who all have predicted straight As, good UCAS forms etc. It's inevitable that some good students will not get in, and it doesn't imply discrimination.

Only some UK universities have a collegiate system (Oxford, Cambridge, Durham, St. Andrews(?)). Most do not (I believe) and I imagine are roughly similar to US universities. At collegiate universities there is a split between what a college is responsible for, and what the university is responsible for. Lectures are university-wide, exams also are (you get your degree from the university not the college), departments belong to the university (so if the Enlgish department needs a new building then the university pays for that). All students (and staff) are affiliated to a college (you choose which college to apply to when you apply to the university, and the college decides whether to admit you). The college is responsible for their students accommodation needs, will usually provide a dining option, common room etc. The college provides teaching (so you go to the same lectures as everyone else, but your small group teaching, feedback on work etc. is organised by the college). I think those are the main distinctions.

Given that the colleges are different, this can mean it's important to choose the right one for you. For example, at Cambridge, Trinity College has an illustrious history in mathematics, and attracts excellent staff, so if you're accepted there then you might end up being taught one-on-two by a world renowned mathematician (Fields Medal winning Timothy Gowers for example). Other colleges with less of a reputation might have more trouble attracting the same type of staff. (this isn't to say that being an expert in your field makes you an excellent teacher of course...)

Although you then have to solve two problems; optimizing the constraints, and then optimizing within the constraints.

If I applied the arbitrary constraint that x must be an odd multiple of pi, then I'm not going to get a very good answer to trying to maximise cos(x)...

I think you're generally right that people would normally choose the better prices. A few hypothetical reasons why someone might not could be: once fees/commissions are included the exchange with the worse price could actually be cheaper; an exchange might offer a rebate based on volume so trading on the more expensive exchange could help someone gain a larger rebate; if you wanted to trade a large quantity immediately in one order, and your quantity was greater than the quantity available at the best price, then you'd need to eat into the order book, and the resulting average price might be cheaper on the more expensive exchange; you might be banned from the cheaper exchange and so would have to trade on the more expensive one.

I'm not really sure what you're talking about.

A market participant will choose which exchange to execute a trade on based on their analysis of those exchanges. If for a particular trade they decide that out of all the exchanges, darkpools and this new lightpool available to them that the exchange that is most suited to that order is the lightpool, then they'll probably route it there. What do you expect them to do? If you're going to buy or sell something then there's an associated cost to doing that whether you do it on the NYSE, in a darkpool, or in this new lightpool.

Credit Suisse don't 'own' any customers, people who trade on this exchange will have no obligation to trade there, it sounds like you think that there are people who are forced to trade through Credit Suisse and so will be forced to use an exchange run by Credit Suisse. That is not the case. If they don't like what is on offer at Credit Suisse then they can trade directly in a market, or they can use another broker.

There are markets outside of the US though, where it would be possible to buy on the more expensive exchange.

They're not shafting anyone, no one will be obliged to trade on this market. People are only going to trade on it if they believe they'll gain some advantage through doing it - so conversely you could argue that by offering this service Credit Suisse are doing their customers a favour.

Well, here's a situation where it can't happen:

    Exchange A: Price you can BUY  ACME Co. = $34.50       
    Exchange B: Price you can BUY  ACME Co. = $34.45    
    Exchange B: Price you can SELL ACME Co. = $34.40    
    Exchange A: Price you can SELL ACME Co. = $34.35

> You type in words that you expect to be in the pages you're looking for, and the search engine lists pages that actually contain ALL of those words.

It's not as simple as that though is it? Otherwise how would those GoogleBombs or whatever they're called work where searching for 'warmongering idiot' or something turn up George Bush's biography on whitehouse.gov. I think search result quality is a bit more involved than just testing whether a page contains a set of words.