Not only will O'Caml detect this error at compile time, it can do so without forcing the programmer [to] write type declarations everywhere.
Only if the object's type is explicit at some point in the function call tree at compile time, I suppose. I can think of dynamic scenaroios where this would not be knowable at compile time.
Static checking as you describe would involve propogating type information from the called function up through its callers while that call sequence is being checked. While nobody does this for Ruby (I think Matz's Ruby compiler is still in alpha-test) it's theoretically possible.
Hm. Is it possible to add DBC to Ruby? Has anyone already done it? There are enough instrumentation entry points in Ruby that you could probably do it without modifying the interpreter.
You have two options with scaffolds: let them be generated every time the program starts, or get the code generated into view source code that you can edit from then on. So, you either have code that you don't have to maintain at all, or code that's yours. Pick the best for what you're doing. It's brief and clear code. If you use the generated-every-time option, you can override it method-by-method simply be creating a view source file for that method.
Ruby doesn't contradict the Object Oriented programming paradigm. If you go back to the origins of OO in Smalltalk, it was much closer to Ruby than some tightly-typed OO languages like C++ and Java. Perhaps the lesson to be learned is that tight typing of class references isn't that good an idea.
Maintainability is a combination of several factors. Most important is: can you
read and understand the code? Ruby on Rails wins in this category because it's
brief - smaller and thus easier to comprehend than Java - without being cryptic
like APL. Second most important is: is it easily modified? Here Rails wins again, because of the say it only once philosophy and because of Ruby's duck typing *. Say-it-once means that you don't have to track down the other
places where you've had to say the same thing (as in Java) and change them. Duck typing means you can change an object substantially without the user of that object seeing the change, because the user only knows what methods the object is expected to respond to, not the object's type.
Bruce
* Duck typing: If it looks like a duck and sounds like a duck, it's a duck! Object types don't matter to the users of Ruby objects. What matters is that the
object responds to a particular collection of methods. This is something like virtual functions, but does not require inheritance from any class or virtual class although inheritance from a Ruby module (sort of an abstract base class) is often the best way to implement those methods. So, a Ruby object might
export a collection of methods called Enumerable and would respond positively to an is_enumerable? method to identify that those services are available.
Generating reverse noise would require that you guess random numbers correctly before they happen. But these numbers are the result of a manmade signal. If you had perfect knowledge of all of the data on the wire (possible) and were able to integrate perfectly and in real time the electromagnetic characteristics of the 3-D world around you for some distance and to an extremely high resolution (very impossible, even if all of that stuff held still), you could do it.
A signal modulated with perfect efficiency would have a frequency spectrum indistinguishable from that of noise. Practical signals only approach the spectrum of noise. But they are anough like the noise that it is not generally possible to isolate one from the other.
I know that NASA can filter out a fraction of a milliwatt signal out of the background noise of the entire universe as well as the noise from the electronic spectrum in the atmosphere.
The main feats there are subperb antennas and amplification. This is exactly the sort of application that could not handle additional noise. They start out with a really big dish antenna, hundreds of feet in diameter - or the one at Aricebo which could cover a town. Sometimes they gang several of them together with a phasing network to get an even tighter focus. The antenna they use is accurate in its dimensions to a small fraction of a wavelength at the frequency of interest, pointed in exactly the right direction. And the amplifier at the feed horn is a carefully picked gallium arsenide transistor made very cold to eliminate quantum noise. Domestic noise is reduced because they are far from habitation (although sites like the Hat Creek Observatory near Mt. Lassen have already been forced off of low frequencies by local development - and the housing there is neither close nor dense nor provided with BPL). The antenna is physically shielded from the horizon, and they may even enforce a radio quiet zone as the U.S. does in North Carolina.
There is a fundamental issue with everything that I've described so far. If the noise is coming from the same direction as the signal, you amplify the noise too.
After the wonderful antennas and the amplification, they use the best DSP available to pick out whatever signal is there.
Turn up the interference and those folks are out of business. Take a look at all of the false-alarm signals the SETI project picks up using that same equipment. They are generally from aircraft, and would obscure observations at the same frequency. Indeed, radio astronomers have quite a problem with aircraft noise these days.
NSA does amazing things too.
Among other things they are GNU Radio users, and have ordered a number of Universal Software Radio Peripheral boards. The radio astronomy folks use that too. You can try this stuff out - the software is free and the hardware relatively inexpensive - and get a better idea of what you can and can not do with DSP. Both the software and the hardware were developed by Radio Amateurs and many of us are experimenting with it.
I know Am Radio covers alot of bands but if you have one you want to pick up, you should be able to design a bandpass (notch) filter to pass only the signal.
Well, if you bandpass filter noise, you still get noise, just a lower bandwidth of it. And you still have to make the signal of interest powerful enough at the reciever to stand out within the noise.
I don't know the characteristics of the signals and noise to see how much the noise would affect the signal. Has anyone done this math?
Oh yes.. There is well-known math for calculating the link power budget - the power you need to reliably overcome ambient noise, atmospheric attenuation, etc. Noise is one of the main terms, along with such things as antenna gain, processing gain, power, and bandwidth. Although you can do things about the noise, even with all possible help your signal has to be strong enough to overcome that noise or you don't have a link. It does follow directly from Shannon's work. I'd imagine it's in basic books on RF engineering.
600K in the USA? Licensed operators? That seems high. Maybe that many licenses but not that many active.
They have to renew their licenses every 10 years, so these are not graveyard voters. There are always a lot of people talking when I turn on my radio. Even a lot of people using code, and digital communications.
Broadband interfernece filters..they exist, I've worked on enough Gov't comm projects to know they do.
There are various kinds of DSP filters. They make the signal sound better, more comfortable to listen to, and sometimes can recover a marginal signal and make it readable. But if you turn the noise up even higher, they're sunk. It's actually theoretically impossible to do much about broadband noise, Shannon's information theory explains a lot of that. What you can do to well with digital filtering is filter out discrete freqencies like hetrodying carriers, and notch a narrow band where the information you want to recieve is, and you can make a channel sound quiet if your signal is sufficiently well above the noise that you can determine which is signal and which is noise. But all of these are still vulnerable to broadband noise. Turn the noise up more, and they fail. You can remove broadband noise that comes from a point-source with an antenna phasing network that nulls it out, but BPL is a distributed - not point - source. You can recover spread-spectrum signals using processing gain, but this is a power-for-bandwidth trade that is still vulnerable to noise.
The bottom line is: if you have high-level noise of the kind that would come from RF-unfriendly BPL systems, you're pretty sunk.
Yes, I am already involved in lobbying about this, both through ARRL and on my own. There are indeed several overriding interests that should protect Amateur Radio from BPL. One is emergency communications, use of those frequencies for education in technology and experimentation are another.
ARRL doesn't have any reason to fib about BPL. If it wasn't making interference, it wouldn't bother them or their membership. On the other hand, the BPL manufacturers and operators have reasons to lie about their potential for interference. They want to make money from their systems without having to build the technology necessary to get along with another spectrum users. BPL is really a marginal proposition - it has to compete with cable and DSL which don't have these problems and can deliver more to the customer because their physical transports are better. Thus, if BPL doesn't make it work cheaply, it won't be profitable.
Unfortunately, digital signal processing doesn't elmimiate broadband interference. When you have enough noise, you can't pick out the signal no matter what your algorithm is.
We're not just talking about a hobby here. These are the emergency communicators who may save your life next. And it's not a few thousand hams. There are 600K in this country alone. But even if it were only hobbyists, we don't allow commerce to tread rough shod over people's leisure, otherwise that bike lane would be another lane for cars and you'd work 16 hours every day, including weekends.
Radio-unfriendly BPL systems are just another sort of pollution. The manufacturers can make non-polluting equipment and the operators can use it. We'll continue to fight their lies until they behave.
Well, you have it wrong in a number of ways. First, the BPL signals have to propogate through the transformer and down the 110/220 wires into homes and businesses where you will plug in your BPL modem. So, the interference goes wherever people live, work, etc. And of course the longer the antenna the better at those frequencies - if you want your signal to go long distances. Power lines are very long compared to other radio antennas. Signals in the range of 1-30 MHz with less than one watt of power have worldwide range when the ionospheric "weather" is right - and with the wide bands used by BPL, the weather will be "right" on some frequencies all of the time.
You may better understand that it doesn't take "hundreds of watts" to interfere when you consider that the interference need only be above the level of a more distant signal - which also has that inverse-square-law propogation. A miliwatt in the right place - where the reciever is - will take out a distant high-powered signal. Take a look at the amount of RF that recievers expect - it's really miniscule - fractions of microvolts.
I think the Cincinatti system is one that has been reported to have problems, yes. Check out the ARRL web site and search for old news.
Unfortunately, the FCC rules don't protect the hams, because they define the degree of protection necessary incorrectly by several orders of magnitude.
When the flooding happened in New Orleans, nearly 1000 well-trained hams showed up to supplement the efforts of the hams who already lived there. The government physically kept them out for a few days (who knows what they were thinking) but had eventually to let them in because they were essential to recovery efforts. You can't really have emergency communications on a "disaster" scale without hams. There isn't another corps of 600,000 trained volunteer communicators in our country to draw upon. And you can't have large-scale disaster communications without 1-30 MHz, as these are the only frequencies that go long distances without infrastructure between the communicating stations.
Most power companies are regulated, and it is very unlikely that they will go to a regulator and ask to lower prices because their expenses have gone down. Especially if they've only gone down by the amount necessary to pay the poor slob who reads your meter at most once a month. But the power companies have had low-rate narrow-band PLC (power-line carrier) for something like 50 years and could have used it for this. They use it to run their facilities and collect telemetry. So, there is IMO sero potential that this will lower prices.
ARRL and Motrola have demonstrated a BPL system that doesn't cause problems. It does not carry the internet signal on the medium-voltage wires (the ones before the transformer). It uses wireless for that and goes to BPL after the transformer and operates something like homeplug. This way, you don't need to shove a ton of power down the line to get a 0-80 MHz broadband signal through a 60 Hz transformer. But few (or no) BPL providers use the Motorola system.
There are also inexplicable errors in the FCC rules, like an interference contour that is wrong by several orders of magnitude.
Hm. Sun's main objection to SISSL - in their complaints to me - has been something like "it allowed IBM to fork OpenOffice and not give anything back". My answer was mostly "yes, that's what you were trying to allow when you created SISSL". People who object to GPL generally only think about the perspective of the recipient of GPL software rather than that of the grantor. But I think the copyright assignment policy is much more relevant to the problem than SISSL vs. LGPL, especially in the context of Sun's contract with Microsoft.
I think an interoperable office suite is necessary for the Linux desktop. I guess Gnumeric interoperates pretty well with Excel, but my impression has been that Abiword does not interoperate as well as OpenOffice Writer and that there isn't another PowerPoint-compatible. I haven't looked at KOffice lately, so please do tell if it makes the grade for these applications.
German comments aren't so hard to figure out. "puffer" is "buffer", and we have machine translation these days, so I'm not so sure that's the problem with OpenOffice. Also, the KDE team has a large Norwegian and German complement. It could be the code is hard to understand, but look at the Linux kernel, which is no picnic to understand and has an incredible community.
I'm more familiar with Evolution. I'd call it an open source project, even though it was developed almost exclusively by Ximian/Novell employees. Is it not?
Evolution and Nautilus had the heavy lifting done by Ximian and Eazel, but both projects were carried out as subsystems of the larger GNOME project, rather than as stand-alone Open Source projects. My impression was that the larger GNOME community was involved, if not actively collaborating, that the intent was always to have the GNOME team accept those tools - and that the companies would thus have to meet GNOME's quality standards. The tools did have to go through GNOME's quality processes eventually, including, I remember, some usability work led by Sun.
I don't know much first-hand about how Eclipse went on, but wasn't there a consortium with a lot of companies as members? I'd assume initially not Sun, since blocking the sun is what eclipses are for, but I remember that Sun did eventually get involved.
Sorry, Bruce, but you're going to have to explain this one because that just doesn't make much sense to me. Does "Open Source project" mean "something that's got an open source license and a big, de-centralized community of developers"?
Yes. To get the full benefit of Open Source, you need a big enough community to drive work for many different agendas rather than mostly one agenda. The problem is tha OO is still mostly Sun. If this were GNOME, for example (which is a project upon which Sun shares work as am equal partner with a large community) quality would be higher.
And all of this makes me sad because the program is so important to the Linux desktop.
OO is Open Source because it's Open Source licensed. The OpenOffice project falls somewhat short of achieving all of the benefits of an Open Source project due to a lack of community, and that in turn is due to some of Sun's decisions about the project policies and about their corporate communications concerning Open Source over several years.
Sun hasn't every been successful at building a viable outside community for OpenOffice. And thus, it's not really an Open Source project, it's just Open Source licensed.
I think some of this has historicaly been a trust problemn, and some has been their copyright assignment policy (which is also a trust problem).
A self-assembling virus is as likely to infect your brain as your computer. Either is so unlikely that it's not worth consideration.
Rather, any extraterrestrial easter-egg would come with instructions for building the machine on which it would execute, and would bait people into building it with promises of an oracle of extraterrestrial knowledge.
Since we have yet to recieve the first bit of data from an extraterrestrial intelligence, I'm not going to worry about that.
Open Source refers only to software with a license that complies with the Open Source Definition. That document was created as the Debian Free Software Guidelines and was blessed by RMS as a good definition of Free Software.
The development model is important, but is not part of the definition of Open Source and software that is developed solely by one guy or one company, as Monty Wirzenius and (later) MySQL AB developed the MySQL server entirely inside of their company, is still Open Source even though it does not share the development model.
If Open Source had community participation as a prerequisite, it would never be created. It's almost always created by one person or group and then opened up for community participation.
Although there has been some divergence between Open Source and Free Software, that was driven by personalities that are now irrelevant, not by any real philosophical difference. The two names still refer to the same thing.
Control is a good word to say to business people. Freedom is something they get to appreciate after they have control for a while, and start thinking about why:-)
Slashdot Mirror
Hm. Then perhaps the best way to maintain code quality is to change languages every few years :-)
Thanks
Bruce
Only if the object's type is explicit at some point in the function call tree at compile time, I suppose. I can think of dynamic scenaroios where this would not be knowable at compile time.
Static checking as you describe would involve propogating type information from the called function up through its callers while that call sequence is being checked. While nobody does this for Ruby (I think Matz's Ruby compiler is still in alpha-test) it's theoretically possible.
Thanks
Bruce
Thanks
Bruce
Bruce
Thanks
Bruce
Bruce
Oops. Duck typing is like virtual base classes, not virtual functions.
Bruce
* Duck typing: If it looks like a duck and sounds like a duck, it's a duck! Object types don't matter to the users of Ruby objects. What matters is that the object responds to a particular collection of methods. This is something like virtual functions, but does not require inheritance from any class or virtual class although inheritance from a Ruby module (sort of an abstract base class) is often the best way to implement those methods. So, a Ruby object might export a collection of methods called Enumerable and would respond positively to an is_enumerable? method to identify that those services are available.
A signal modulated with perfect efficiency would have a frequency spectrum indistinguishable from that of noise. Practical signals only approach the spectrum of noise. But they are anough like the noise that it is not generally possible to isolate one from the other.
Bruce
The main feats there are subperb antennas and amplification. This is exactly the sort of application that could not handle additional noise. They start out with a really big dish antenna, hundreds of feet in diameter - or the one at Aricebo which could cover a town. Sometimes they gang several of them together with a phasing network to get an even tighter focus. The antenna they use is accurate in its dimensions to a small fraction of a wavelength at the frequency of interest, pointed in exactly the right direction. And the amplifier at the feed horn is a carefully picked gallium arsenide transistor made very cold to eliminate quantum noise. Domestic noise is reduced because they are far from habitation (although sites like the Hat Creek Observatory near Mt. Lassen have already been forced off of low frequencies by local development - and the housing there is neither close nor dense nor provided with BPL). The antenna is physically shielded from the horizon, and they may even enforce a radio quiet zone as the U.S. does in North Carolina.
There is a fundamental issue with everything that I've described so far. If the noise is coming from the same direction as the signal, you amplify the noise too.
After the wonderful antennas and the amplification, they use the best DSP available to pick out whatever signal is there. Turn up the interference and those folks are out of business. Take a look at all of the false-alarm signals the SETI project picks up using that same equipment. They are generally from aircraft, and would obscure observations at the same frequency. Indeed, radio astronomers have quite a problem with aircraft noise these days.
NSA does amazing things too.
Among other things they are GNU Radio users, and have ordered a number of Universal Software Radio Peripheral boards. The radio astronomy folks use that too. You can try this stuff out - the software is free and the hardware relatively inexpensive - and get a better idea of what you can and can not do with DSP. Both the software and the hardware were developed by Radio Amateurs and many of us are experimenting with it.
I know Am Radio covers alot of bands but if you have one you want to pick up, you should be able to design a bandpass (notch) filter to pass only the signal.
Well, if you bandpass filter noise, you still get noise, just a lower bandwidth of it. And you still have to make the signal of interest powerful enough at the reciever to stand out within the noise.
I don't know the characteristics of the signals and noise to see how much the noise would affect the signal. Has anyone done this math?
Oh yes.. There is well-known math for calculating the link power budget - the power you need to reliably overcome ambient noise, atmospheric attenuation, etc. Noise is one of the main terms, along with such things as antenna gain, processing gain, power, and bandwidth. Although you can do things about the noise, even with all possible help your signal has to be strong enough to overcome that noise or you don't have a link. It does follow directly from Shannon's work. I'd imagine it's in basic books on RF engineering.
Bruce
Thanks
Bruce
They have to renew their licenses every 10 years, so these are not graveyard voters. There are always a lot of people talking when I turn on my radio. Even a lot of people using code, and digital communications.
Broadband interfernece filters..they exist, I've worked on enough Gov't comm projects to know they do.
There are various kinds of DSP filters. They make the signal sound better, more comfortable to listen to, and sometimes can recover a marginal signal and make it readable. But if you turn the noise up even higher, they're sunk. It's actually theoretically impossible to do much about broadband noise, Shannon's information theory explains a lot of that. What you can do to well with digital filtering is filter out discrete freqencies like hetrodying carriers, and notch a narrow band where the information you want to recieve is, and you can make a channel sound quiet if your signal is sufficiently well above the noise that you can determine which is signal and which is noise. But all of these are still vulnerable to broadband noise. Turn the noise up more, and they fail. You can remove broadband noise that comes from a point-source with an antenna phasing network that nulls it out, but BPL is a distributed - not point - source. You can recover spread-spectrum signals using processing gain, but this is a power-for-bandwidth trade that is still vulnerable to noise.
The bottom line is: if you have high-level noise of the kind that would come from RF-unfriendly BPL systems, you're pretty sunk.
Yes, I am already involved in lobbying about this, both through ARRL and on my own. There are indeed several overriding interests that should protect Amateur Radio from BPL. One is emergency communications, use of those frequencies for education in technology and experimentation are another.
Bruce
Unfortunately, digital signal processing doesn't elmimiate broadband interference. When you have enough noise, you can't pick out the signal no matter what your algorithm is.
We're not just talking about a hobby here. These are the emergency communicators who may save your life next. And it's not a few thousand hams. There are 600K in this country alone. But even if it were only hobbyists, we don't allow commerce to tread rough shod over people's leisure, otherwise that bike lane would be another lane for cars and you'd work 16 hours every day, including weekends.
Radio-unfriendly BPL systems are just another sort of pollution. The manufacturers can make non-polluting equipment and the operators can use it. We'll continue to fight their lies until they behave.
Bruce
You may better understand that it doesn't take "hundreds of watts" to interfere when you consider that the interference need only be above the level of a more distant signal - which also has that inverse-square-law propogation. A miliwatt in the right place - where the reciever is - will take out a distant high-powered signal. Take a look at the amount of RF that recievers expect - it's really miniscule - fractions of microvolts.
I think the Cincinatti system is one that has been reported to have problems, yes. Check out the ARRL web site and search for old news.
Unfortunately, the FCC rules don't protect the hams, because they define the degree of protection necessary incorrectly by several orders of magnitude.
When the flooding happened in New Orleans, nearly 1000 well-trained hams showed up to supplement the efforts of the hams who already lived there. The government physically kept them out for a few days (who knows what they were thinking) but had eventually to let them in because they were essential to recovery efforts. You can't really have emergency communications on a "disaster" scale without hams. There isn't another corps of 600,000 trained volunteer communicators in our country to draw upon. And you can't have large-scale disaster communications without 1-30 MHz, as these are the only frequencies that go long distances without infrastructure between the communicating stations.
Bruce
Bruce
ARRL and Motrola have demonstrated a BPL system that doesn't cause problems. It does not carry the internet signal on the medium-voltage wires (the ones before the transformer). It uses wireless for that and goes to BPL after the transformer and operates something like homeplug. This way, you don't need to shove a ton of power down the line to get a 0-80 MHz broadband signal through a 60 Hz transformer. But few (or no) BPL providers use the Motorola system.
There are also inexplicable errors in the FCC rules, like an interference contour that is wrong by several orders of magnitude.
Bruce
Bruce
German comments aren't so hard to figure out. "puffer" is "buffer", and we have machine translation these days, so I'm not so sure that's the problem with OpenOffice. Also, the KDE team has a large Norwegian and German complement. It could be the code is hard to understand, but look at the Linux kernel, which is no picnic to understand and has an incredible community.
Bruce
Evolution and Nautilus had the heavy lifting done by Ximian and Eazel, but both projects were carried out as subsystems of the larger GNOME project, rather than as stand-alone Open Source projects. My impression was that the larger GNOME community was involved, if not actively collaborating, that the intent was always to have the GNOME team accept those tools - and that the companies would thus have to meet GNOME's quality standards. The tools did have to go through GNOME's quality processes eventually, including, I remember, some usability work led by Sun.
I don't know much first-hand about how Eclipse went on, but wasn't there a consortium with a lot of companies as members? I'd assume initially not Sun, since blocking the sun is what eclipses are for, but I remember that Sun did eventually get involved.
Bruce
Yes. To get the full benefit of Open Source, you need a big enough community to drive work for many different agendas rather than mostly one agenda. The problem is tha OO is still mostly Sun. If this were GNOME, for example (which is a project upon which Sun shares work as am equal partner with a large community) quality would be higher.
And all of this makes me sad because the program is so important to the Linux desktop.
OO is Open Source because it's Open Source licensed. The OpenOffice project falls somewhat short of achieving all of the benefits of an Open Source project due to a lack of community, and that in turn is due to some of Sun's decisions about the project policies and about their corporate communications concerning Open Source over several years.
Bruce
I think some of this has historicaly been a trust problemn, and some has been their copyright assignment policy (which is also a trust problem).
Thanks
Bruce
Rather, any extraterrestrial easter-egg would come with instructions for building the machine on which it would execute, and would bait people into building it with promises of an oracle of extraterrestrial knowledge.
Since we have yet to recieve the first bit of data from an extraterrestrial intelligence, I'm not going to worry about that.
Bruce
The development model is important, but is not part of the definition of Open Source and software that is developed solely by one guy or one company, as Monty Wirzenius and (later) MySQL AB developed the MySQL server entirely inside of their company, is still Open Source even though it does not share the development model.
If Open Source had community participation as a prerequisite, it would never be created. It's almost always created by one person or group and then opened up for community participation.
Although there has been some divergence between Open Source and Free Software, that was driven by personalities that are now irrelevant, not by any real philosophical difference. The two names still refer to the same thing.
Bruce
Bruce