The data in executable bytestreams has a large amount of redundancy. Therefore there are lots of "wasted" bits which can be fiddled with to store data. The site's slashdotted but I assume this works by replacing certain instructions in the binary with other, equivalent instructions.
There is a definite limit on the amount of data you can embed without increasing the file size, because a finite file can only have a finite amount of redundancy.
Perhaps the author thought this was too obvious to mention. I certainly didn't get the impression he was claiming the ability to embed arbitrary amounts of data in tiny executable files.
If you embed a signiature of the file into the file, this by definition changes the file's signiature.
It is typically assumed for these kinds of things that the signature itself is not part of the data being signed.
However if the file can be modified, so can it's signiature.
You could easily solve that by using X.509 certificates, issues by a trusted CA, similar to the Microsoft "signcode.exe" program for signing CAB files and EXEs. However, that would only prove the integrity of the binary. It's still impossible to write a program which refuses to run when modified, because you can always just remove the code that checks the validity of the signature. That's the real paradox.
Either that, or the author is misinformed to a degree I don't think I've seen before...
png uses Run Length Encoding (RLE) to compress the images.
It does not. PNG uses a set of predictive filters on a row-by-row basis and then applies zlib "deflate" compression to the transformed rows. This is the same compression as used in gzip. Programs like pngcrush operate by trying different combinations of predictive filters and pixel modes to see which achieves the highest compression.
So anywhere in an image that you see large expanses of color is where png will excel.
This is correct, but not because it uses run-length encoding. The predictive filters reduce many rows to a single color, and the deflate compression can compress these very effectively.
It's also where jpg is going to fall down
You can easily disprove this by making a large color image of one solid color, then JPEG compressing it. JPEG handles solid color absolutely fine.
jpg (which uses fractal compression) essentially records the "roughness" of an image.
It has nothing to do with fractals or "roughness." It transforms 8x8 blocks of image data into the frequency domain, quantizes the resulting cosine basis function coefficients, arranges the quantized coefficients in a special order, applies a maximum frequency threshold, and outputs the coefficients using Huffman codes.
I have hyperhydrosis, which essentially makes my hands sweat more than normal.
These days there is a surgical procedure, thoracoscopic sympathectomy, to cure this. Basically, they cut into your spine and sever a nerve near the spinal cord. This stops the sweating.
How does point size have anything to do with eye strain? The paper is still the same distance away from your face regardless of the size of the letters on the paper. Your eyes focus the same in either case.
I thought we'd moved beyond the medieval superstition that looking at certain kinds of things can damage your eyes...
The original author can display their tab characters as equivalent to 8 or whatever, and you can view it as 4 or whatever. That's the genius of using tabs for indentation.
If you think indentation should be done with tabs then logically you must oppose the 80-column limitation.
Think about it. Suppose my tab stops are 2 columns, and I'm tabbed three levels in, and I write a line of code that extends over to column 78. Now, somebody with 4 column tab stops opens my code and suddenly the line is indented by 12 characters instead of 6 and that same line of code now extends over to column 84. There goes your precious 80-column limitation.
If you like the idea of an 80-column limit on code, then you MUST use spaces to indent, not tabs.
If you "win" (ie. make money), it does not necessarily mean that someone else "lost" (lost money).
In order for both people to profit in a transaction, money must be created somehow. Either money flowed into the country from some other country (in which case, the other country got poorer), or the government created more money (which will eventually just lead to a devaluation of the dollar anyway).
In a closed economic system where the government is not synthesizing money out of thin air, what you're talking about is impossible. If it's not zero sum, where did the net increase come from?
Unless dollars have found a way to breed in my wallet, I think you're not making any sense.
Considering Google probably gets a billion hits a day, easily, that's 365 billion hits a year. If you guess that each ad impression nets Google one cent, that's $3.65 billion a year just in advertising revenue.
Not to mention the value of the technology and know-how of the top people working on the Google search engine. How much is that worth? Well, in a free market, it's worth what people are willing to pay for it. In this case, we're looking at around $30 billion for the entire company.
I assert that if people are willing to value Google at $30 billion, then Google is, in fact, worth $30 billion. With hard advertising revenue of at least $3.65 billion a year, and God-knows-what sort of intellectual property, I'd say a $30 billion evaluation is not unreasonable at all.
True, the black sail will heat up from the absorbed proton. However the heat escaping from the sail will add to it's inital velocity.
First, it isn't absorbing protons. It is absorbing light. If it was absorbing protons, the sail would be charging up to an enormous voltage.
And if by "heat escaping from the sail" you mean infrared radiation, yes, that would exert a pressure on the sail, but there is no way to make the radiation go in a single direction. Both sides of the sail would radiate, and the pressures would cancel to no net effect.
If dark objects emit heat faster than lighter objects, then two hot objects placed in the dark (so they're not absorbing more heat from the sun) would cool at different rates, even though made from the same material?
I'm assuming you're referring to a coat of paint on the objects, because if two objects are made of the same material they must surely be the same color, correct?
If you had, say, two identical cubes of wood, at the same temperature, and one was painted white and one was painted black, and the paint was of the same thickness on each, and the thermal conductivity of the paint was identical on each, then the cube painted black would cool faster.
I suppose you might be referring to, for example, different colors of plastic. You could have a black polyurethane sheet, and a white one. However these no longer qualify as the "same material" because the black sheet has had particles of black dye added in order to color it black. The black sheet, although made of polyurethane like the white one, will cool/heat faster.
Now let's go back to the example of the black and white shirts. If the goal is to heat the individual, then clearly the black shirt is better because it absorbs sunlight. Whereas a white shirt can maintain the body heat of the wearer but cannot easily increase it because it cannot absorb sunlight. (In reality the situation is much more complicated because shirts have holes to allow air to pass through.)
Now, take that person out of the sun and stick him in a crater on the moon. Now, a black shirt is a huge liability because it radiates heat much faster than a white shirt would.
When it comes down to radiation and absorption on the surface of an object, all that really matters is the blackness of the surface. It might be the case that a particular white object gets hotter faster in the sun than a particular black object, but that means the white object has a lower thermal conductivity and hence cannot "sink" that heat further into the object. "All other things being equal" is the key phrase here.
I would penalized, regardless of how well I drive, because of my WORK SCHEDULE?
Are you suggesting that the concept of basing insurance premiums on the statistical likelihood of having an accident is unfair? What would be fair, a flat rate for all customers? Think about it.
The property of how well something gives off heat from its surface (I suppose this is what you mean by "radiator") is a property of what material it is--unrelated to what color it is.
I don't know where you are getting this "correct" information, but it isn't. Absorption and emission of radiation are both controlled by the material's emissivity. A material which is twice as effective at absorbing energy (as compared to some baseline) is also twice as effective at radiating it.
Instead of a house, let's say you want to keep a person warm. Which color T-shirt should they wear--white or black? The black one will get warmer as it absorbs more sunlight.
No, the ideal shirt would be aluminized mylar -- perfectly reflective, allowing no body heat to escape. A black shirt warms up in the sun, but in the absence of sun a black shirt is the worst color you could wear, since it will radiate the heat away from your body much faster than a reflective shirt. And no, not because it got "hotter" than a white shirt would have.
Maybe the idea you were going for was that dark-colored objects will give off more heat, but that is because they have absorbed more and therefore have more to give.
Wrong. There is no physical difference between absorption and emission of radiation. They are the same process in different directions. A good absorber is a good radiator. This is made explicit in the equations, which you obviously do not know.
I have more than a trivial knowledge of what I speak...
Computer Science is a facinating field of study, and a great hobby. Its a rotten career. [...] There are very few companies out there that truly respect their programmers
That's the problem right there. You think CS is about programming. I heartily agree that the field of computer programming can be a crap one, but that's not what CS is about.
There are computer scientists working at NASA, writing physical dynamics software. Computer scientists at places like Google who do nothing but write information-theoretic equations on whiteboards all day, trying to enhance search algorithms. There are computer scientists designing machine learning algorithms, robotic control systems, and programs that play Go.
There are computer scientists who spend 8 hours a day thinking about how to optimize the arrangement of boxes in the back of a UPS truck.
It's no wonder you disparage the field of CS, because you've confused it with your daily grind of programming computers. The two are not the same thing at all.
If you can't find ways to make your computer science degree fun and rewarding for you, I think you have an enormous lack of vision. Expect your alternate job with your alternate master's degree to be equally unrewarding. Just switching topics isn't going to fix the fundamental problem, which is that you have no drive.
I wouldn't hire a CS person w/out a CS degree... Otherwise they "think" they know what they're doing but they don't.
Holy shit, this is the most naive comment I've ever seen on Slashdot.
What would you hire a "CS person" for? Choose your answer carefully, because I think it will demonstrate that you have no idea what a "CS person" actually studies, knows, and is good at. Hint: it isn't programming.
Why get a Biology degree and then look for a job in computers? You picked the major so go find a job in it, sheesh.
The arrogance of this comment is astonishing. A college degree indicates that you have dedicated four years of your life to study, work, and long-term goals. It proves that you're able to stick it out even when confronted with nonsense and bullshit. It demonstrates that your mind is flexible enough to apply to many different fields of learning.
Most of all, it demonstrates that you are serious about the outcome of your own life.
Around here, we require college degrees of all employees. It doesn't matter what the degree is in. We've hired philosophy majors as system administrators, electrical engineers as programmers, biology majors as human resources directors, forest management majors as technical support staff, etc. The degree proves a certain level of intelligence and tenacity. The particular subject area is less important.
To make this as easy as possible for insurance company representatives (or any other representatives of big business and government) to understand: Stay the f**k out of my life.
I would posit that insurance companies have, to some degree, a right to examine certain details of your life in exchange for insurance coverage. Otherwise, we'd all have to pay premiums based on the average payout, which would be higher for some and lower for others.
Are you really suggesting I should pay the same for car insurance as a guy who has 50 speeding tickets? And that he should pay less because I'm subsizing his dangerous driving?
To claim that the insurance company should give you a good deal without ever having a chance to examine the very behavior they are insuring is pretty pig-headed, I think. If you don't like it, don't get car insurance. There are other options, like bonding your vehicle with the state.
Do I think mandatory recording of driving habits is a good idea? No. But asserting that the insurance company has no right whatsoever to inquire into your driving history is arrogant and unrealistic.
Re:Still need two good eyes?
on
3D Monitor
·
· Score: 4, Interesting
It really sucks being blind in one eye sometimes.
I would think it would be easier to create 3D display technology for one-eyed individuals than for people with two eyes.
For people with two functioning eyes there are three major depth cues: stereovision, focus, and attenuation. With one eye you still have focus and attenuation, but no stereovision. (You also have parallax as the eye is moving, but this isn't as helpful.) So a one-eyed person doesn't rely on stereovision at all to gauge depth.
Notice that it is only the stereovision which is hard to simulate with a display device -- software could be written to simulate focal blur and distance attenuation, and since these are the only depth cues available to people with a single eye, this should be a pretty convincing representation of a 3D scene.
What I want to see is a 3d hologram platform/table.
Why bother making a physical image when you can just inject visual data directly into the brain? I wager we'll figure out how to do that before we figure out how to make a true 3D projection.
It would be *really* cool if someone set something up that would absorb IR in the winter (like a dark roof) but not in the summer (light roof).
No, you actually still want a light roof in winter. A black roof is a good absorber and a good radiator as well. In the winter, a black roof will radiate the heat out of your house more rapidly than it can heat up from the sun (since the radiant intensity is generally much lower in winter). You still want a light-colored, insulating roof, even in winter.
In areas of the world that receive snowfall in winter, the snow on the roof is actually helping, by reflecting heat back into the building.
Slashdot Mirror
Don't be dense. The part of the file where the hash is written is not included in the hash. Duh.
b = 'hola'
b = 'y' + b[1:]
In general, to replace the n'th char of a string (n=1 is the first char):
str = str[:n-1] + char + str[n:]
There is a definite limit on the amount of data you can embed without increasing the file size, because a finite file can only have a finite amount of redundancy.
Perhaps the author thought this was too obvious to mention. I certainly didn't get the impression he was claiming the ability to embed arbitrary amounts of data in tiny executable files.
It is typically assumed for these kinds of things that the signature itself is not part of the data being signed. However if the file can be modified, so can it's signiature.
You could easily solve that by using X.509 certificates, issues by a trusted CA, similar to the Microsoft "signcode.exe" program for signing CAB files and EXEs. However, that would only prove the integrity of the binary. It's still impossible to write a program which refuses to run when modified, because you can always just remove the code that checks the validity of the signature. That's the real paradox.
png uses Run Length Encoding (RLE) to compress the images.
It does not. PNG uses a set of predictive filters on a row-by-row basis and then applies zlib "deflate" compression to the transformed rows. This is the same compression as used in gzip. Programs like pngcrush operate by trying different combinations of predictive filters and pixel modes to see which achieves the highest compression.
So anywhere in an image that you see large expanses of color is where png will excel.
This is correct, but not because it uses run-length encoding. The predictive filters reduce many rows to a single color, and the deflate compression can compress these very effectively.
It's also where jpg is going to fall down
You can easily disprove this by making a large color image of one solid color, then JPEG compressing it. JPEG handles solid color absolutely fine.
jpg (which uses fractal compression) essentially records the "roughness" of an image.
It has nothing to do with fractals or "roughness." It transforms 8x8 blocks of image data into the frequency domain, quantizes the resulting cosine basis function coefficients, arranges the quantized coefficients in a special order, applies a maximum frequency threshold, and outputs the coefficients using Huffman codes.
You still haven't explained where the dollars come from.
And you assert that natural rubber is not chemical in nature? What is it? Metaphysical?
If they wanted to indicate the artificial nature of the rubber, they could have called it... DUM DUM DUM.... "artificial rubber."
This reminds me of when my grandmother once told me she didn't "want to eat food that has any chemicals in it."
These days there is a surgical procedure, thoracoscopic sympathectomy, to cure this. Basically, they cut into your spine and sever a nerve near the spinal cord. This stops the sweating.
As opposed to spiritual rubber, perhaps.
I thought we'd moved beyond the medieval superstition that looking at certain kinds of things can damage your eyes...
If you think indentation should be done with tabs then logically you must oppose the 80-column limitation.
Think about it. Suppose my tab stops are 2 columns, and I'm tabbed three levels in, and I write a line of code that extends over to column 78. Now, somebody with 4 column tab stops opens my code and suddenly the line is indented by 12 characters instead of 6 and that same line of code now extends over to column 84. There goes your precious 80-column limitation.
If you like the idea of an 80-column limit on code, then you MUST use spaces to indent, not tabs.
Ever heard of lower and upper bounds?
If you'd like to dispute that Google gets a billion hits a day, then dispute it. I think it's perfectly possible.
If you'd like to dispute a $0.01 price per ad impression, then dispute that.
Oh, I get it. What you're saying is that estimation is impossible. Well, that's just brilliant.
In order for both people to profit in a transaction, money must be created somehow. Either money flowed into the country from some other country (in which case, the other country got poorer), or the government created more money (which will eventually just lead to a devaluation of the dollar anyway).
In a closed economic system where the government is not synthesizing money out of thin air, what you're talking about is impossible. If it's not zero sum, where did the net increase come from?
Unless dollars have found a way to breed in my wallet, I think you're not making any sense.
Not to mention the value of the technology and know-how of the top people working on the Google search engine. How much is that worth? Well, in a free market, it's worth what people are willing to pay for it. In this case, we're looking at around $30 billion for the entire company.
I assert that if people are willing to value Google at $30 billion, then Google is, in fact, worth $30 billion. With hard advertising revenue of at least $3.65 billion a year, and God-knows-what sort of intellectual property, I'd say a $30 billion evaluation is not unreasonable at all.
First, it isn't absorbing protons. It is absorbing light. If it was absorbing protons, the sail would be charging up to an enormous voltage.
And if by "heat escaping from the sail" you mean infrared radiation, yes, that would exert a pressure on the sail, but there is no way to make the radiation go in a single direction. Both sides of the sail would radiate, and the pressures would cancel to no net effect.
I'm assuming you're referring to a coat of paint on the objects, because if two objects are made of the same material they must surely be the same color, correct?
If you had, say, two identical cubes of wood, at the same temperature, and one was painted white and one was painted black, and the paint was of the same thickness on each, and the thermal conductivity of the paint was identical on each, then the cube painted black would cool faster.
I suppose you might be referring to, for example, different colors of plastic. You could have a black polyurethane sheet, and a white one. However these no longer qualify as the "same material" because the black sheet has had particles of black dye added in order to color it black. The black sheet, although made of polyurethane like the white one, will cool/heat faster.
Now let's go back to the example of the black and white shirts. If the goal is to heat the individual, then clearly the black shirt is better because it absorbs sunlight. Whereas a white shirt can maintain the body heat of the wearer but cannot easily increase it because it cannot absorb sunlight. (In reality the situation is much more complicated because shirts have holes to allow air to pass through.)
Now, take that person out of the sun and stick him in a crater on the moon. Now, a black shirt is a huge liability because it radiates heat much faster than a white shirt would.
When it comes down to radiation and absorption on the surface of an object, all that really matters is the blackness of the surface. It might be the case that a particular white object gets hotter faster in the sun than a particular black object, but that means the white object has a lower thermal conductivity and hence cannot "sink" that heat further into the object. "All other things being equal" is the key phrase here.
Are you suggesting that the concept of basing insurance premiums on the statistical likelihood of having an accident is unfair? What would be fair, a flat rate for all customers? Think about it.
I don't know where you are getting this "correct" information, but it isn't. Absorption and emission of radiation are both controlled by the material's emissivity. A material which is twice as effective at absorbing energy (as compared to some baseline) is also twice as effective at radiating it.
Instead of a house, let's say you want to keep a person warm. Which color T-shirt should they wear--white or black? The black one will get warmer as it absorbs more sunlight.
No, the ideal shirt would be aluminized mylar -- perfectly reflective, allowing no body heat to escape. A black shirt warms up in the sun, but in the absence of sun a black shirt is the worst color you could wear, since it will radiate the heat away from your body much faster than a reflective shirt. And no, not because it got "hotter" than a white shirt would have.
Maybe the idea you were going for was that dark-colored objects will give off more heat, but that is because they have absorbed more and therefore have more to give.
Wrong. There is no physical difference between absorption and emission of radiation. They are the same process in different directions. A good absorber is a good radiator. This is made explicit in the equations, which you obviously do not know.
I have more than a trivial knowledge of what I speak...
That's the problem right there. You think CS is about programming. I heartily agree that the field of computer programming can be a crap one, but that's not what CS is about.
There are computer scientists working at NASA, writing physical dynamics software. Computer scientists at places like Google who do nothing but write information-theoretic equations on whiteboards all day, trying to enhance search algorithms. There are computer scientists designing machine learning algorithms, robotic control systems, and programs that play Go.
There are computer scientists who spend 8 hours a day thinking about how to optimize the arrangement of boxes in the back of a UPS truck.
It's no wonder you disparage the field of CS, because you've confused it with your daily grind of programming computers. The two are not the same thing at all.
If you can't find ways to make your computer science degree fun and rewarding for you, I think you have an enormous lack of vision. Expect your alternate job with your alternate master's degree to be equally unrewarding. Just switching topics isn't going to fix the fundamental problem, which is that you have no drive.
Holy shit, this is the most naive comment I've ever seen on Slashdot.
What would you hire a "CS person" for? Choose your answer carefully, because I think it will demonstrate that you have no idea what a "CS person" actually studies, knows, and is good at. Hint: it isn't programming.
Why get a Biology degree and then look for a job in computers? You picked the major so go find a job in it, sheesh.
The arrogance of this comment is astonishing. A college degree indicates that you have dedicated four years of your life to study, work, and long-term goals. It proves that you're able to stick it out even when confronted with nonsense and bullshit. It demonstrates that your mind is flexible enough to apply to many different fields of learning.
Most of all, it demonstrates that you are serious about the outcome of your own life.
Around here, we require college degrees of all employees. It doesn't matter what the degree is in. We've hired philosophy majors as system administrators, electrical engineers as programmers, biology majors as human resources directors, forest management majors as technical support staff, etc. The degree proves a certain level of intelligence and tenacity. The particular subject area is less important.
You have no real world experience, do you?
I would posit that insurance companies have, to some degree, a right to examine certain details of your life in exchange for insurance coverage. Otherwise, we'd all have to pay premiums based on the average payout, which would be higher for some and lower for others.
Are you really suggesting I should pay the same for car insurance as a guy who has 50 speeding tickets? And that he should pay less because I'm subsizing his dangerous driving?
To claim that the insurance company should give you a good deal without ever having a chance to examine the very behavior they are insuring is pretty pig-headed, I think. If you don't like it, don't get car insurance. There are other options, like bonding your vehicle with the state.
Do I think mandatory recording of driving habits is a good idea? No. But asserting that the insurance company has no right whatsoever to inquire into your driving history is arrogant and unrealistic.
I would think it would be easier to create 3D display technology for one-eyed individuals than for people with two eyes.
For people with two functioning eyes there are three major depth cues: stereovision, focus, and attenuation. With one eye you still have focus and attenuation, but no stereovision. (You also have parallax as the eye is moving, but this isn't as helpful.) So a one-eyed person doesn't rely on stereovision at all to gauge depth.
Notice that it is only the stereovision which is hard to simulate with a display device -- software could be written to simulate focal blur and distance attenuation, and since these are the only depth cues available to people with a single eye, this should be a pretty convincing representation of a 3D scene.
Wow dude, are you really so insecure about your sexuality that you can't stand seeing male actors in porn?
Why bother making a physical image when you can just inject visual data directly into the brain? I wager we'll figure out how to do that before we figure out how to make a true 3D projection.
No, you actually still want a light roof in winter. A black roof is a good absorber and a good radiator as well. In the winter, a black roof will radiate the heat out of your house more rapidly than it can heat up from the sun (since the radiant intensity is generally much lower in winter). You still want a light-colored, insulating roof, even in winter.
In areas of the world that receive snowfall in winter, the snow on the roof is actually helping, by reflecting heat back into the building.