Us astute readers have also noted that your earth-massed black hole is going to pull on you with a lot more than 1G if you're going to be that close to it.
You're right, that's why I said "adjust masses to achieve appropriate effect outside the Schwarzchild radius". I stated that badly, my point was that you're very close to the object's center of gravity, so the mass needs to be adjusted.
If you were 1,080 miles from this black hole (radius of Earth)
Finally, a chance to say "what planet are you on?" in a meaningful context! Please hand your astute reader card in on your way out. The radius of Earth is more like 3980 miles...;)
Now like electromagnetism, gravity is one of the four fundamental forces. If we can create a shield to block one of them why not block gravity?
Hmm, although I agree it's difficult to say that shielding against gravity is impossible, the above is not exactly sound logic. You need to look at the origin of the forces in question to see why.
The general relativistic model of gravity as the effect of warped spacetime would seem to indicate that blocking gravity could be a fundamentally different problem than blocking electromagnetic radiation.
Electromagnetic radiation travels through spacetime, i.e. it follows the curvature of spacetime. Blocking it is simply a matter of constructing the right kind of interfering device, such as a faraday cage, to prevent electromagnetic photons/wave packets from penetrating.
OTOH, according to GR, gravity as we perceive it is essentially a secondary effect due to the curvature of spacetime. To "block" it, you would have to be able to uncurve spacetime in the vicinity you wish to block. This is a little different from blocking photons. The only thing we've ever discovered that's capable of warping spacetime is "mass". So sure, we can counter the effects of gravity, there's no mystery about it: simply use a mass as large as the mass of the object whose gravitational effects you want to counter.
Unfortunately, in the case of gravity, this doesn't really work the way we want. Let's say I create a black hole with a similar mass to that of the Earth (I have a fairly well-equipped basement). In the vicinity of the black hole, I would feel a force towards the hole (please no goatse jokes) of approximately 1G (adjust masses to achieve appropriate effect outside the Schwarzchild radius, etc.) So if I hang the black hole from my ceiling, I could create a micro-gravity environment in my basement, with the force upward cancelling the force downward.
Astute readers have by now noticed a slight problem with this scenario. Despite my well-equipped basement, I don't happen to possess a means for suspending an Earth-mass object a few feet above another Earth-mass object (i.e. the Earth itself). There's not going to be a heck of a lot I can do about the fact that my black hole is going to shoot down towards the earth under a combined force of 2G and a momentum that would require numbers with "E" in them to describe. (I had better not be standing beneath it, if I want to avoid rather nasty tidal effects as the black hole travels through my body - that killed a guy on Mars once.)
Because of the nature of gravity, "shielding" against its effects may not even be meaningful. Even if it is possible, it's highly doubtful that we will stumble across the solution by random experimentation with e.g. spinning disks. Spinning disks might confuse researchers, but they don't confuse the universe.
You're welcome. Some of the most interesting computer science I've come across has been from googling based on Slashdot messages...;)
You have a valid point that it's not possible to rely on recursion always being as efficient as iteration in a given language or language implementation, so for maximum efficiency, you have to become familiar with the capabilities and quirks of the system you're using. That's true of many other features also, though.
This is a big reason that recursion gets a somewhat bad rap: mainstream languages have virtually zero support for it (other than e.g. tail call support in gcc), and support in other languages varies wildly. I expect over the next decade or so, we'll start seeing better recursion support in mainstream languages.
Actually, most of these terms should be liberally enclosed in scare quotes. I'm assuming all sorts of things
Ditto.
We may be talking at cross purposes. If we tell someone to do something consciously, we can be reasonably sure that if they subsequently do it, that at some point, a concious decision was made to do it. It's easy to test that this is not some kind of automatic response to instruction, certainly.
In addition, it's easy to determine that a truly conscious decision to do something (as opposed to something which may appear conscious after the fact) must precede the action itself. Here's a way to prove this: look at a coffee cup, say out loud "I'm going to lift that coffee cup", and then lift the coffee cup. Did a conscious decision precede the action? If you say no, then we have to start redefining our terms, since I say it does, inevitably.
What I think you're focusing on is how and when conscious decisions get communicated to the parts of our brain and body that actually cause physical actions to be executed. I agree that this mechanism is probably wholly unconscious.
In the CD player example, I'm saying that a conscious decision is made by the subject, *prior to the action*. However, for all we know, this conscious decision may be made quite some time ahead of the action - we really have no way to tell. As a software developer, I would use the analogy of queuing an event request. Having made the conscious decision to perform an action, an event request is queued. At some point after that, the action is performed, by an unconscious mechanism. The exact timing of our initiation of the action is out of our control in a similar way as it is in a software system: there may be other higher-priority events queued, garbage collection may need to take place (software analogy), etc.
So when you say "But, the point of the CD experiment is to show that it's not a conscious decision", I believe that by "it", in the context of this discussion, you mean the unconscious initiation of an action which was triggered by a prior conscious decision. I don't think there's any mystery here, and in fact I think psych folk might benefit from writing some real-time software to gain an intuitive feel for some of these things. Of course, that's one of the points of AI work on things like autonomous robots.
BTW, one of the many automatic processes that must take place in any real-time system (including us!) is the synchronization of perception of external events with internal processes. Anyone who writes real-time software sooner or later runs into a situation where delay in detecting external events must be taken into account, since catastrophic errors can result otherwise, as the effects of the delay are compounded over time. So software effectively has to set back the timestamp on external events - often by different amounts depending on the kind of event or other factors. From the point of view of a control program, which compares timestamps, it sees events happening in the appropriate sequence, even though reality may be different depending on how and where you measure it. Our consciousness exhibits a similar effect, which is hardly surprising.
So my comment about orthogonality is that the CD player experiment is measuring the things I've just described, relating to things like execution of queued actions and perception delays, i.e. the aftereffects of a conscious decision. It doesn't say anything about the initial conscious decision that led to this activity.
Note that I'm not saying all decisions are conscious; just that some are, and that it's possible to control for conscious decisions. When such a conscious decision occurs, it necessarily must precede the action which is taken as a result. However, the final mechanism by which that action is taken is primarily unconscious.
It may be the case that there is an "unconscious conscious" that has "free will" but that doesn't appear in the forefront of consciousness.
That may well be true, but isn't what I was talking about.
Or, what is consciousness? (I.e., is consciousness just awareness, or is that only a small part of consciousness.)
The terms are very overloaded, but "conscious decisions" are not quite as vague as consciousness, and that's really what we're talking about. The definition I've been using is of a decision made deliberately with the awareness of our conscious minds (some recursiveness there, can't be helped), prior to the actual execution of that decision. By this definition, because of the reasons we've discussed, some decisions may seem to be conscious that in fact aren't; nevertheless, it is possible to control for this in lab environments by appropriate interaction with the participants.
The point is that rather than having a causal chain that looks like:
decide to raise hand -> raise hand
it's more like:
hand raises -> consciousness says 'I meant to do that.'
This is an example of an "unconscious" action, though, like scratching your nose. I'm familiar with variations on the studies you describe. I did a year of undergrad psych, which means I may not even know enough to be dangerous. However, I don't think the quote above covers the case of a consciously motivated action. There are actions that are "unconscious", to which our consciousness may nevertheless attribute conscious motivation (e.g. nose-scratching) - and there are actions which are consciously initiated, but like all actions, have to be routed through the usual nervous system channels. These channels operate unconsciously, so the causal chain for "decide to raise hand/raise hand" is really something like:
* decide to raise hand * hand-raising instruction issued as result of decision * hand raises, under control of nervous system (including associated brain function) * consciousness says "I meant to do that" - and it's right.
Your CD player example, as described, might simply illustrate the lag between signalling in the body and physical motion. I'm familiar with other experiments which have shown the retcon effect you're describing, but I don't think there's anything too mysterious about it: it's a simple necessity to sync external events with our perceptions - not just our own actions, but other external activity as well. But even if the actual study took this into account, it still doesn't say anything about whether the original motivation was conscious or not.
In fact, based on studies that have been done of how people's perception can change if continually exposed to some distortion in their environment (like seeing everything upside down), if you gave someone a set of goggles that delayed everything by an extra half-second, I suspect their brain would soon adjust to increase the retcon period. But this issue is orthogonal to the question of the initiation of actions being conscious or unconscious.
Hmmm. It isn't clear from your post whether you're aware that all recursion can automatically be transformed into iteration. This was the point of my statement that recursion and iteration are mathematically equivalent, i.e. each can be converted into the other following well-defined rules. This makes such conversion quite amenable to automated transformation, e.g. by compiler.
In fact, in the CPS intermediate representation for compiled code, commonly used for functional languages, *all* calls are converted to tail calls, automatically. CPS conversion and subsequent closure optimization allows functions to be written recursively, without worrying about tail calls, and converted by the compiler into an iterative tail call form, where possible.
Re:Not about computer science; try SICP instead
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I don't like math much though I adore logic)
I also tend to prefer the logic side of things. A lot of computer science of the kind that SICP deals with has to do with mathematical logic, which I find more logic-like than math-like.
For that reason, I love the lambda calculus, which is what almost all functional programming is based on.
If you like logic, and you like programming, you *must* learn the lambda calculus - it'll give you new insight into the meaning of computer programming, and you'll probably enjoy it, too. It has applications to literally every programming language. If you're not already familiar with lambda calculus, the name sounds a lot more daunting than it really is. To start out with, you can think of it as a really simple and primitive programming language - almost the prototypical programming language.
I'm not sure what the best intro source into lambda calculus is - the academic works are mostly heavier-duty than you really need. Some google searching definitely turns up some useful stuff, but offhand I don't know of a definitive intro site. However, SICP teaches a lot of the necessary fundamentals, since the Scheme language that it uses as a teaching tool is just about the closest language to the lambda calculus that there is. If you learn a bit of Scheme first, learning lambda calculus from the lay perspective is fairly straightforward. (I say "lay perspective" because it has some hairy mathematical underpinnings, which I mostly ignore, and that's OK for most purposes unless you're trying to prove mathematical theories.)
(ie: I know to how to program, but not how to make good programs. Every tome i need to add unexpected features or when I review my old stupid ugly code, I am reminded of that fact:-)
...And then there's programming under a deadline, which is a whole 'nother story.
I think that these academic topics can be excellent for improving one's design and thinking skills, at least I've found that to be the case. It's an indirect kind of thing, though, and experience is probably equally useful. Abstraction is key, though, whether you do it using object-orientation or modules in functional programs, keeping interfaces separate from implementations is probably one of the most important things, which people violate all the time. It doesn't help that many languages don't provide features to do this properly...
Isn't looping a subset of recursion, or a limited way of recursion?
Any recursion can be translated into a loop, and vice versa, so the answer is no. However, it's certainly true that recursion is usually more expressive than looping, i.e. more concise and communicative of the intent of the code.
If recursion and looping were not equivalent, there would be operations which you could not do without one or the other approach (or you'd need a third alternative), but that's not the case. The equivalence of recursion and loops can be proved via a formal mathematical proof - which qualifies as real computer science, btw.
An easy way to prove it mentally is to construct a general rule for translating recursion to a loop: simply declare each of the original recursive function's parameters as an array, and use the loop index to index into that array. Of course, many recursive operations can be loopified more efficiently than this.
You could argue that in going to the trouble of implementing recursive behavior as a loop, you're effectively implementing recursion, and thus no longer looping at all; but that kind of proves the point that there really isn't much difference between the two, conceptually.
A loop is like a recursion in which you declare all function variables as globals, you can't pass arguments (can't declare anything local). And with no return functionality?
That's reasonably accurate, although I would replace "can't" with "less convenient".
Re:Not about computer science; try SICP instead
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We want it for free:(
The link I gave to SICP includes the full text in HTML. How much more free do you need it to be? It's accessible by clicking the link on that page which reads "Full text! The complete text in HTML". Unintuitive, I know, but that's the kind of thing you'll learn to understand as a computer scientist...
though many of the critics are ineed covered in the book: naming of variables, abstracting and not hardcoding stuff, making it readable, making it generic, wrapping code, etc.
These things have very little to do with computer science, with the exception of abstraction (which has very little to do with "not hardcoding stuff"). What we have here is a situation where people who know absolutely nothing about the current practice of computer science are using the term to mean whatever they imagine it means.
Variable naming, readability, wrapping code etc. all involve techniques which any good programmer should understand, academic or otherwise. But calling that computer science is like calling hammering a nail "civil engineering" or "materials science". The Python book, at best, could be described as an intro guide to software engineering, but even that's a stretch. It's really "how to program in Python", with a few technical terms introduced along the way.
Sorry, but you're confused
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While Python is my favourite language, I think it's rather silly to teach Computer Science and especially basic algorithmics with a language that doesn't have pointers.
At low level, pointers are everything, and low level is what you want to teach when you're teaching basic data structures and algorithms.
Conceptually and from a computer science perspective, the object references present in languages like Python, Java etc. are equivalent to pointers in all the ways that matter for representation of data structures and algorithms. In the academic community and elsewhere, it's generally considered beneficial to teach such things without reference to the machine pointers which you're referring to, since machine pointers carry a lot of baggage that's unrelated to the abstractions involved in data structures and algorithms.
There's simply no point in demonstrating list implementation with an interpreted language that has very efficient native lists, dictionaries, etc.
To refute this, let me offer a tutorial: A Gentle Introduction to ML. If you work through this tutorial, you'll very soon begin implementing functions in the ML language for basic list operations and the like - functions that already exist in the language. And guess what: the implementations that the beginner typically comes up with in that tutorial are very close to the actual implementations that ML uses - the tutorial gives some examples of actual implementations for comparison.
This high-level operation doesn't even cost much -languages in the ML family, including OCaml, regularly are top performers - see e.g. Doug Bagley's language shootout. They can perform on par with languages like C because their type systems allow sophisticated compile-time optimizations to be performed, and their high-level abstraction features are supported by optimizations such as tail recursion.
C/C++ or Pascal are much better for that; with them you can teach real implementations, not toy ones.
If you believe that C/C++ and Pascal are good languages for teaching computer science, you don't know much about modern computer science. All three of those languages have very weak type systems and lack basic features that allow the construction of high-level abstractions.
Pascal is all but a dead language in the CS community nowadays. The primary use for C is as a decent portable assembler. Learning C has very little to do with computer science, and absolutely nothing to do with teaching computer science concepts.
I would rather focus on the idea of getting Federal matching funds for Open Source than proving I'm a worthy soul.
Good response. I just replied to one of your other posts about your tax deduction idea, but when I saw this I wanted to add: getting Federal matching funds for Open Source is not a bad idea, but I think you may be looking in the wrong direction when it comes to the IRS. However, the Federal government gives out grants for all sorts of things, and it would seem to make more sense to look in that direction for ways in which open source might fit into existing programs.
But I doubt you'll find some existing loophole that allows you to simply receive cash for open source by just filling out a form. More likely, with a lot of political lobbying etc., it might be possible to get the government to be more receptive to funding open source projects that are in the public interest. However, you'll have to fight lobbies of commercial software makers who feel threatened, so it's not likely to be easy.
If you want to be realistic instead of ideological (no value judgement there, just being pragmatic), you might have more luck finding a business which is interested in contributing towards the work in question.
Re: land yourself in jail for evasion
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What after all is so bloody dangerous about the idea of people create great works of value, donating them to the public, and getting some "public compensation"?
When it comes to taxes, the definition of "bloody dangerous" is set by the tax department, and pretty much equates to "anything that reduces tax revenues".
I'm not a tax person, but I think Sheldon may have gotten it right in his original answer to you. Imagine if, instead of donating one of your works, you sold it instead, and then turned around and donated that money. It's a net wash to you - you got income, but you donated it, so you don't pay tax on that income.
In your scenario, you're conveniently leaving out the bit where you receive income for the work. When you donate it, you're taking a tax deduction based on income you never received. A fairly basic point about taxes is that deductions are almost always based on your income, they're not free gifts of cash from the government.
So, it seems to me that any tax department in the world is likely to take a dim view of your idea, since it essentially involves the tax department paying you, rather than you paying them and them giving you deductions. Once again, the tax department is not in the business of giving out cash grants, whether for public works or otherwise.
Your Bill Gates example doesn't really wash for this same reason: he takes deductions from the taxes that he's paying, based on his income. You want to take deductions based on no income. Allowing you to do that would be tantamount to allowing you to print your own dollar bills.
Not about computer science; try SICP instead
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That's because it's not about Software Engineering, you fool. It's about Computer Science.
If you actually look at the book in question, you'll see that the original poster was correct: it's not about computer science at all. It's a Python programming book with a marketing angle relating it to computer science.
If you really want a book which teaches "How to Think Like a Computer Scientist", try SICP. For a good summary of the book, see this comment from the recent "Best Computer Books" article.
I still hate scheme not everything should be recursive.
Sounds like you didn't actually learn the lesson. Recursion and loops are mathematically equivalent - if you see a difference between the two, it's only in your head (and perhaps on the stack of a language that doesn't properly support it).
All of the most sophisticated languages available today make recursion a very natural part of their operation: the ML family, including OCaml; Haskell; and of course, Scheme. Here's a factorial function in ML:
fun fact 0 = 1 | fact n = n * fact(n-1);
All it says is "the factorial of 0 is 1; the factorial of n is n times the factorial of n-1". Of course, factorial might be called a naturally recursive function, but the point is that in languages that support recursion, recursion is as natural as looping, and in fact usually much clearer in terms of communicating what's happening.
If you'd like to learn about recursion in a very natural way, try A Gentle Introduction to ML, which is an excellent tutorial. You don't have to get very far into it before it becomes obvious how useful and natural recursion can be.
What's special about the DMCA is the extreme degree of punitiveness of the penalties it allows. For the "offense" Perens was planning to commit, it makes no sense (except to an RIAA member) that anyone should be on the hook for years in jail and $500,000 in fines - especially considering that the offense in question is actually no offense at all, under previously extant accepted legal fair use principles.
So my point is that the DMCA protects itself against challenges by being so extreme - if no one is willing to violate it and test its legality in court, and may be left standing despite the fact that it violates long-established legal principles.
Aside from anything else, this is rather disturbing in its implications for future laws: to avoid challenges to bad laws, the creators simply have to make sure that the punishment is serious enough to discourage such challenges. Allowing the DMCA to stand sets a bad example for future corporate-sponsored laws. Corporations are succeeding in creating large, blunt instruments that they can wield without ever going to court. Yes, this has long been the case in the US legal system, but the DMCA is an extreme example.
It doesn't sounds as though you understand the issues that the DMCA raises. You're not alone, and this is one of the reasons that the DMCA has remained unchallenged for as long as it has.
I'm plenty old enough to pay for CDs, and I do. I've occassionally previewed downloaded music, but I haven't stolen a penny from the RIAA, by any definition. But this is so far from being the issue with the DMCA that it's not even funny. I don't have time to write up an essay about it right now, but I'll try to encapsulate it briefly.
The DMCA represnts an unprecedented extension of copyright and intellectual property (IP) powers in favor of the IP owners. IP owners now have the right to control your use of their creations in ways that they previously, under established fair use laws, did not have a right to do. In addition, if you choose to circumvent the law - as people do all the time, such as when speeding or parking illegally - you are then subject to extremely punitive fines and jail sentences.
Your point about hardship is irrelevant. For the record, I fled the country of my birth, under threat of arrest for a non-violent political offense. I've experienced life under a non-democratic government. Yes, the situation may be worse for other people and in other places, and the DMCA is not as serious as, say, the rule of the Taliban was. Does that mean we should simply give up more of our freedoms to corporations who want more money and greater control over our wallets and our actions? Obviously not. It's an irrelevant point.
Another subject that's poorly understood in these discussions is what intellectual property really means. There's longstanding legal precedent which acknowledges that creators of IP benefit from access to the public domain in creating their works, which is why laws only allow an IP owner limited control over their works for a limited period of time. IP owners like Disney, however, have succeeded in gutting this principle in the law, and the DMCA extends this gutting much further, eliminating many forms of what was previously considered legal fair use.
There's a common myth that intellectual "property" should be legally treated like any other property, but just a little thought and applied intelligence indicates that this is clearly not the case.
In my opinion, much of what's in the DMCA will not survive when it finally reaches the point of being properly tested up to the Supreme Court level, because it violates basic premises of what is in the public interest. Unfortunately, the DMCA itself provides enormous disincentives to challenging it - in the form of extreme fines and sentences for even minor acts - which was the point of my original post.
Wallace seems to have is own agenda based around pushing the Alicebot. I've interacted with Alicebots myself, and obviously one doesn't really try to challenge it since it soon becomes apparent how limited it is. Sitting on Alice's side, as Wallace does, looking at the responses from people and concluding something about those people is like watching adults interact with a baby and concluding that the human vocabulary consists of lots of words like "goo-goo", said in a high-pitched tone of voice.
You're also correct about the math issue: we're good computers for certain preprogrammed tasks, which makes us little different than any other computing device. He's complaining that we're not good at reprogramming ourselves to do tasks for which we weren't specifically evolved, but in that sense he can't compare us to computers, since they also can only perform the tasks they're programmed for, and have no consciousness of the processes they perform.
Wallace is a smartish guy with some apparently serious social skills problems (ref NYT article posted on/. previously), and he seems to be using Alice as a shield/weapon against the rest of the world.
[The male bower bird] seems to make conscious decisions about how best to design the nest. However, attributing consciousness to the bower bird is an iffy proposition. I have a hard time imagining a bower bird with an interior monologue:
BB: Yeah, baby. Check out those shells. I gotsta get me some of them for my swingin' bachelor pad. I'm gonna be pimpin' like a mother once I get hooked up with some of that shit. Those fly hoochies will be all over my jimmy! Damn.
Great example, but I think you have that a bit backwards. I don't have a problem attributing some bird-like equivalent of that internal dialog to the bower bird - but I would have trouble attributing true "consciousness" to a person saying that to themselves while beachcombing. In the person's case, the internal dialog probably serves a function as a kind of check/balance on the activity, but doesn't necessarily denote a high level of consciousness.
Part of the problem here may be definitional: the apparently "conscious" decisions which the bower bird makes don't necessarily imply "consciousness" in the sense that we normally use it. Then again, interacting with a well-trained parrot, one gets the sense that something more than mere instinct is operating in its tiny brain, albeit a limited form of whatever it is. But that's the Turing Test all over again - how do we know the parrot isn't just fooling us into thinking it's intelligent - and is their actually any difference between being able to fool someone into thinking you're intelligent, and actually being intelligent?
This is an excellent example of how the DMCA can have a chilling effect on free speech without even having to be tested in court. People often focus on the law itself as the threat, but as much of a threat can be how companies and individuals behave in response to the law - self-policing can sometimes be the worst kind.
Since Slide is not specifically intended for source code management, I would imagine subversion has many features in this area that Slide does not. However, I haven't used either, only read about them.
If you're looking for something to embed/extend and you know Java, then Slide would make sense, especially if you're planning to use it for something other than source code management. However, you might still want to use subversion for the source of that project... Most people don't need to extend their source code manager much, except perhaps with a few scripts.
Slashdot Mirror
You're right, that's why I said "adjust masses to achieve appropriate effect outside the Schwarzchild radius". I stated that badly, my point was that you're very close to the object's center of gravity, so the mass needs to be adjusted.
Finally, a chance to say "what planet are you on?" in a meaningful context! Please hand your astute reader card in on your way out. The radius of Earth is more like 3980 miles... ;)
AFAIK, there are no consistent quantum theories of gravity, so I'm sticking to my story...
Hmm, although I agree it's difficult to say that shielding against gravity is impossible, the above is not exactly sound logic. You need to look at the origin of the forces in question to see why.
The general relativistic model of gravity as the effect of warped spacetime would seem to indicate that blocking gravity could be a fundamentally different problem than blocking electromagnetic radiation.
Electromagnetic radiation travels through spacetime, i.e. it follows the curvature of spacetime. Blocking it is simply a matter of constructing the right kind of interfering device, such as a faraday cage, to prevent electromagnetic photons/wave packets from penetrating.
OTOH, according to GR, gravity as we perceive it is essentially a secondary effect due to the curvature of spacetime. To "block" it, you would have to be able to uncurve spacetime in the vicinity you wish to block. This is a little different from blocking photons. The only thing we've ever discovered that's capable of warping spacetime is "mass". So sure, we can counter the effects of gravity, there's no mystery about it: simply use a mass as large as the mass of the object whose gravitational effects you want to counter.
Unfortunately, in the case of gravity, this doesn't really work the way we want. Let's say I create a black hole with a similar mass to that of the Earth (I have a fairly well-equipped basement). In the vicinity of the black hole, I would feel a force towards the hole (please no goatse jokes) of approximately 1G (adjust masses to achieve appropriate effect outside the Schwarzchild radius, etc.) So if I hang the black hole from my ceiling, I could create a micro-gravity environment in my basement, with the force upward cancelling the force downward.
Astute readers have by now noticed a slight problem with this scenario. Despite my well-equipped basement, I don't happen to possess a means for suspending an Earth-mass object a few feet above another Earth-mass object (i.e. the Earth itself). There's not going to be a heck of a lot I can do about the fact that my black hole is going to shoot down towards the earth under a combined force of 2G and a momentum that would require numbers with "E" in them to describe. (I had better not be standing beneath it, if I want to avoid rather nasty tidal effects as the black hole travels through my body - that killed a guy on Mars once.)
Because of the nature of gravity, "shielding" against its effects may not even be meaningful. Even if it is possible, it's highly doubtful that we will stumble across the solution by random experimentation with e.g. spinning disks. Spinning disks might confuse researchers, but they don't confuse the universe.
The Moller Flying Car.
You have a valid point that it's not possible to rely on recursion always being as efficient as iteration in a given language or language implementation, so for maximum efficiency, you have to become familiar with the capabilities and quirks of the system you're using. That's true of many other features also, though.
This is a big reason that recursion gets a somewhat bad rap: mainstream languages have virtually zero support for it (other than e.g. tail call support in gcc), and support in other languages varies wildly. I expect over the next decade or so, we'll start seeing better recursion support in mainstream languages.
Ditto.
We may be talking at cross purposes. If we tell someone to do something consciously, we can be reasonably sure that if they subsequently do it, that at some point, a concious decision was made to do it. It's easy to test that this is not some kind of automatic response to instruction, certainly.
In addition, it's easy to determine that a truly conscious decision to do something (as opposed to something which may appear conscious after the fact) must precede the action itself. Here's a way to prove this: look at a coffee cup, say out loud "I'm going to lift that coffee cup", and then lift the coffee cup. Did a conscious decision precede the action? If you say no, then we have to start redefining our terms, since I say it does, inevitably.
What I think you're focusing on is how and when conscious decisions get communicated to the parts of our brain and body that actually cause physical actions to be executed. I agree that this mechanism is probably wholly unconscious.
In the CD player example, I'm saying that a conscious decision is made by the subject, *prior to the action*. However, for all we know, this conscious decision may be made quite some time ahead of the action - we really have no way to tell. As a software developer, I would use the analogy of queuing an event request. Having made the conscious decision to perform an action, an event request is queued. At some point after that, the action is performed, by an unconscious mechanism. The exact timing of our initiation of the action is out of our control in a similar way as it is in a software system: there may be other higher-priority events queued, garbage collection may need to take place (software analogy), etc.
So when you say "But, the point of the CD experiment is to show that it's not a conscious decision", I believe that by "it", in the context of this discussion, you mean the unconscious initiation of an action which was triggered by a prior conscious decision. I don't think there's any mystery here, and in fact I think psych folk might benefit from writing some real-time software to gain an intuitive feel for some of these things. Of course, that's one of the points of AI work on things like autonomous robots.
BTW, one of the many automatic processes that must take place in any real-time system (including us!) is the synchronization of perception of external events with internal processes. Anyone who writes real-time software sooner or later runs into a situation where delay in detecting external events must be taken into account, since catastrophic errors can result otherwise, as the effects of the delay are compounded over time. So software effectively has to set back the timestamp on external events - often by different amounts depending on the kind of event or other factors. From the point of view of a control program, which compares timestamps, it sees events happening in the appropriate sequence, even though reality may be different depending on how and where you measure it. Our consciousness exhibits a similar effect, which is hardly surprising.
So my comment about orthogonality is that the CD player experiment is measuring the things I've just described, relating to things like execution of queued actions and perception delays, i.e. the aftereffects of a conscious decision. It doesn't say anything about the initial conscious decision that led to this activity.
Note that I'm not saying all decisions are conscious; just that some are, and that it's possible to control for conscious decisions. When such a conscious decision occurs, it necessarily must precede the action which is taken as a result. However, the final mechanism by which that action is taken is primarily unconscious.
It may be the case that there is an "unconscious conscious" that has "free will" but that doesn't appear in the forefront of consciousness.
That may well be true, but isn't what I was talking about.
Or, what is consciousness? (I.e., is consciousness just awareness, or is that only a small part of consciousness.)
The terms are very overloaded, but "conscious decisions" are not quite as vague as consciousness, and that's really what we're talking about. The definition I've been using is of a decision made deliberately with the awareness of our conscious minds (some recursiveness there, can't be helped), prior to the actual execution of that decision. By this definition, because of the reasons we've discussed, some decisions may seem to be conscious that in fact aren't; nevertheless, it is possible to control for this in lab environments by appropriate interaction with the participants.
decide to raise hand -> raise hand
it's more like:
hand raises -> consciousness says 'I meant to do that.'
This is an example of an "unconscious" action, though, like scratching your nose. I'm familiar with variations on the studies you describe. I did a year of undergrad psych, which means I may not even know enough to be dangerous. However, I don't think the quote above covers the case of a consciously motivated action. There are actions that are "unconscious", to which our consciousness may nevertheless attribute conscious motivation (e.g. nose-scratching) - and there are actions which are consciously initiated, but like all actions, have to be routed through the usual nervous system channels. These channels operate unconsciously, so the causal chain for "decide to raise hand/raise hand" is really something like:
* decide to raise hand
* hand-raising instruction issued as result of decision
* hand raises, under control of nervous system (including associated brain function)
* consciousness says "I meant to do that" - and it's right.
Your CD player example, as described, might simply illustrate the lag between signalling in the body and physical motion. I'm familiar with other experiments which have shown the retcon effect you're describing, but I don't think there's anything too mysterious about it: it's a simple necessity to sync external events with our perceptions - not just our own actions, but other external activity as well. But even if the actual study took this into account, it still doesn't say anything about whether the original motivation was conscious or not.
In fact, based on studies that have been done of how people's perception can change if continually exposed to some distortion in their environment (like seeing everything upside down), if you gave someone a set of goggles that delayed everything by an extra half-second, I suspect their brain would soon adjust to increase the retcon period. But this issue is orthogonal to the question of the initiation of actions being conscious or unconscious.
In fact, in the CPS intermediate representation for compiled code, commonly used for functional languages, *all* calls are converted to tail calls, automatically. CPS conversion and subsequent closure optimization allows functions to be written recursively, without worrying about tail calls, and converted by the compiler into an iterative tail call form, where possible.
I also tend to prefer the logic side of things. A lot of computer science of the kind that SICP deals with has to do with mathematical logic, which I find more logic-like than math-like. For that reason, I love the lambda calculus, which is what almost all functional programming is based on.
If you like logic, and you like programming, you *must* learn the lambda calculus - it'll give you new insight into the meaning of computer programming, and you'll probably enjoy it, too. It has applications to literally every programming language. If you're not already familiar with lambda calculus, the name sounds a lot more daunting than it really is. To start out with, you can think of it as a really simple and primitive programming language - almost the prototypical programming language.
I'm not sure what the best intro source into lambda calculus is - the academic works are mostly heavier-duty than you really need. Some google searching definitely turns up some useful stuff, but offhand I don't know of a definitive intro site. However, SICP teaches a lot of the necessary fundamentals, since the Scheme language that it uses as a teaching tool is just about the closest language to the lambda calculus that there is. If you learn a bit of Scheme first, learning lambda calculus from the lay perspective is fairly straightforward. (I say "lay perspective" because it has some hairy mathematical underpinnings, which I mostly ignore, and that's OK for most purposes unless you're trying to prove mathematical theories.)
(ie: I know to how to program, but not how to make good programs. Every tome i need to add unexpected features or when I review my old stupid ugly code, I am reminded of that fact :-)
I think that these academic topics can be excellent for improving one's design and thinking skills, at least I've found that to be the case. It's an indirect kind of thing, though, and experience is probably equally useful. Abstraction is key, though, whether you do it using object-orientation or modules in functional programs, keeping interfaces separate from implementations is probably one of the most important things, which people violate all the time. It doesn't help that many languages don't provide features to do this properly...
Any recursion can be translated into a loop, and vice versa, so the answer is no. However, it's certainly true that recursion is usually more expressive than looping, i.e. more concise and communicative of the intent of the code.
If recursion and looping were not equivalent, there would be operations which you could not do without one or the other approach (or you'd need a third alternative), but that's not the case. The equivalence of recursion and loops can be proved via a formal mathematical proof - which qualifies as real computer science, btw.
An easy way to prove it mentally is to construct a general rule for translating recursion to a loop: simply declare each of the original recursive function's parameters as an array, and use the loop index to index into that array. Of course, many recursive operations can be loopified more efficiently than this.
You could argue that in going to the trouble of implementing recursive behavior as a loop, you're effectively implementing recursion, and thus no longer looping at all; but that kind of proves the point that there really isn't much difference between the two, conceptually.
A loop is like a recursion in which you declare all function variables as globals, you can't pass arguments (can't declare anything local). And with no return functionality?
That's reasonably accurate, although I would replace "can't" with "less convenient".
The link I gave to SICP includes the full text in HTML. How much more free do you need it to be? It's accessible by clicking the link on that page which reads "Full text! The complete text in HTML". Unintuitive, I know, but that's the kind of thing you'll learn to understand as a computer scientist...
though many of the critics are ineed covered in the book: naming of variables, abstracting and not hardcoding stuff, making it readable, making it generic, wrapping code, etc.
These things have very little to do with computer science, with the exception of abstraction (which has very little to do with "not hardcoding stuff"). What we have here is a situation where people who know absolutely nothing about the current practice of computer science are using the term to mean whatever they imagine it means.
Variable naming, readability, wrapping code etc. all involve techniques which any good programmer should understand, academic or otherwise. But calling that computer science is like calling hammering a nail "civil engineering" or "materials science". The Python book, at best, could be described as an intro guide to software engineering, but even that's a stretch. It's really "how to program in Python", with a few technical terms introduced along the way.
At low level, pointers are everything, and low level is what you want to teach when you're teaching basic data structures and algorithms.
Conceptually and from a computer science perspective, the object references present in languages like Python, Java etc. are equivalent to pointers in all the ways that matter for representation of data structures and algorithms. In the academic community and elsewhere, it's generally considered beneficial to teach such things without reference to the machine pointers which you're referring to, since machine pointers carry a lot of baggage that's unrelated to the abstractions involved in data structures and algorithms.
There's simply no point in demonstrating list implementation with an interpreted language that has very efficient native lists, dictionaries, etc.
To refute this, let me offer a tutorial: A Gentle Introduction to ML. If you work through this tutorial, you'll very soon begin implementing functions in the ML language for basic list operations and the like - functions that already exist in the language. And guess what: the implementations that the beginner typically comes up with in that tutorial are very close to the actual implementations that ML uses - the tutorial gives some examples of actual implementations for comparison.
This high-level operation doesn't even cost much -languages in the ML family, including OCaml, regularly are top performers - see e.g. Doug Bagley's language shootout. They can perform on par with languages like C because their type systems allow sophisticated compile-time optimizations to be performed, and their high-level abstraction features are supported by optimizations such as tail recursion.
C/C++ or Pascal are much better for that; with them you can teach real implementations, not toy ones.
If you believe that C/C++ and Pascal are good languages for teaching computer science, you don't know much about modern computer science. All three of those languages have very weak type systems and lack basic features that allow the construction of high-level abstractions.
Pascal is all but a dead language in the CS community nowadays. The primary use for C is as a decent portable assembler. Learning C has very little to do with computer science, and absolutely nothing to do with teaching computer science concepts.
Good response. I just replied to one of your other posts about your tax deduction idea, but when I saw this I wanted to add: getting Federal matching funds for Open Source is not a bad idea, but I think you may be looking in the wrong direction when it comes to the IRS. However, the Federal government gives out grants for all sorts of things, and it would seem to make more sense to look in that direction for ways in which open source might fit into existing programs.
But I doubt you'll find some existing loophole that allows you to simply receive cash for open source by just filling out a form. More likely, with a lot of political lobbying etc., it might be possible to get the government to be more receptive to funding open source projects that are in the public interest. However, you'll have to fight lobbies of commercial software makers who feel threatened, so it's not likely to be easy.
If you want to be realistic instead of ideological (no value judgement there, just being pragmatic), you might have more luck finding a business which is interested in contributing towards the work in question.
When it comes to taxes, the definition of "bloody dangerous" is set by the tax department, and pretty much equates to "anything that reduces tax revenues".
I'm not a tax person, but I think Sheldon may have gotten it right in his original answer to you. Imagine if, instead of donating one of your works, you sold it instead, and then turned around and donated that money. It's a net wash to you - you got income, but you donated it, so you don't pay tax on that income.
In your scenario, you're conveniently leaving out the bit where you receive income for the work. When you donate it, you're taking a tax deduction based on income you never received. A fairly basic point about taxes is that deductions are almost always based on your income, they're not free gifts of cash from the government.
So, it seems to me that any tax department in the world is likely to take a dim view of your idea, since it essentially involves the tax department paying you, rather than you paying them and them giving you deductions. Once again, the tax department is not in the business of giving out cash grants, whether for public works or otherwise.
Your Bill Gates example doesn't really wash for this same reason: he takes deductions from the taxes that he's paying, based on his income. You want to take deductions based on no income. Allowing you to do that would be tantamount to allowing you to print your own dollar bills.
If you actually look at the book in question, you'll see that the original poster was correct: it's not about computer science at all. It's a Python programming book with a marketing angle relating it to computer science.
If you really want a book which teaches "How to Think Like a Computer Scientist", try SICP. For a good summary of the book, see this comment from the recent "Best Computer Books" article.
Sounds like you didn't actually learn the lesson. Recursion and loops are mathematically equivalent - if you see a difference between the two, it's only in your head (and perhaps on the stack of a language that doesn't properly support it).
All of the most sophisticated languages available today make recursion a very natural part of their operation: the ML family, including OCaml; Haskell; and of course, Scheme. Here's a factorial function in ML:
All it says is "the factorial of 0 is 1; the factorial of n is n times the factorial of n-1". Of course, factorial might be called a naturally recursive function, but the point is that in languages that support recursion, recursion is as natural as looping, and in fact usually much clearer in terms of communicating what's happening.If you'd like to learn about recursion in a very natural way, try A Gentle Introduction to ML, which is an excellent tutorial. You don't have to get very far into it before it becomes obvious how useful and natural recursion can be.
As should people who complain about it on Slashdot. The remaining group would be a relaxed bunch of people with good spelling and grammar!
So my point is that the DMCA protects itself against challenges by being so extreme - if no one is willing to violate it and test its legality in court, and may be left standing despite the fact that it violates long-established legal principles.
Aside from anything else, this is rather disturbing in its implications for future laws: to avoid challenges to bad laws, the creators simply have to make sure that the punishment is serious enough to discourage such challenges. Allowing the DMCA to stand sets a bad example for future corporate-sponsored laws. Corporations are succeeding in creating large, blunt instruments that they can wield without ever going to court. Yes, this has long been the case in the US legal system, but the DMCA is an extreme example.
I'm plenty old enough to pay for CDs, and I do. I've occassionally previewed downloaded music, but I haven't stolen a penny from the RIAA, by any definition. But this is so far from being the issue with the DMCA that it's not even funny. I don't have time to write up an essay about it right now, but I'll try to encapsulate it briefly.
The DMCA represnts an unprecedented extension of copyright and intellectual property (IP) powers in favor of the IP owners. IP owners now have the right to control your use of their creations in ways that they previously, under established fair use laws, did not have a right to do. In addition, if you choose to circumvent the law - as people do all the time, such as when speeding or parking illegally - you are then subject to extremely punitive fines and jail sentences.
Your point about hardship is irrelevant. For the record, I fled the country of my birth, under threat of arrest for a non-violent political offense. I've experienced life under a non-democratic government. Yes, the situation may be worse for other people and in other places, and the DMCA is not as serious as, say, the rule of the Taliban was. Does that mean we should simply give up more of our freedoms to corporations who want more money and greater control over our wallets and our actions? Obviously not. It's an irrelevant point.
Another subject that's poorly understood in these discussions is what intellectual property really means. There's longstanding legal precedent which acknowledges that creators of IP benefit from access to the public domain in creating their works, which is why laws only allow an IP owner limited control over their works for a limited period of time. IP owners like Disney, however, have succeeded in gutting this principle in the law, and the DMCA extends this gutting much further, eliminating many forms of what was previously considered legal fair use.
There's a common myth that intellectual "property" should be legally treated like any other property, but just a little thought and applied intelligence indicates that this is clearly not the case.
In my opinion, much of what's in the DMCA will not survive when it finally reaches the point of being properly tested up to the Supreme Court level, because it violates basic premises of what is in the public interest. Unfortunately, the DMCA itself provides enormous disincentives to challenging it - in the form of extreme fines and sentences for even minor acts - which was the point of my original post.
You're also correct about the math issue: we're good computers for certain preprogrammed tasks, which makes us little different than any other computing device. He's complaining that we're not good at reprogramming ourselves to do tasks for which we weren't specifically evolved, but in that sense he can't compare us to computers, since they also can only perform the tasks they're programmed for, and have no consciousness of the processes they perform.
Wallace is a smartish guy with some apparently serious social skills problems (ref NYT article posted on /. previously), and he seems to be using Alice as a shield/weapon against the rest of the world.
Part of the problem here may be definitional: the apparently "conscious" decisions which the bower bird makes don't necessarily imply "consciousness" in the sense that we normally use it. Then again, interacting with a well-trained parrot, one gets the sense that something more than mere instinct is operating in its tiny brain, albeit a limited form of whatever it is. But that's the Turing Test all over again - how do we know the parrot isn't just fooling us into thinking it's intelligent - and is their actually any difference between being able to fool someone into thinking you're intelligent, and actually being intelligent?
This is an excellent example of how the DMCA can have a chilling effect on free speech without even having to be tested in court. People often focus on the law itself as the threat, but as much of a threat can be how companies and individuals behave in response to the law - self-policing can sometimes be the worst kind.
If you're looking for something to embed/extend and you know Java, then Slide would make sense, especially if you're planning to use it for something other than source code management. However, you might still want to use subversion for the source of that project... Most people don't need to extend their source code manager much, except perhaps with a few scripts.
This sounds exactly like Coulter's new book!