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Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
2. No recruiting for your cockamamie projects (you won't replace facebook with 3 dudes you found on the internet and $20)
3. If you can't articulate why a language is bad, don't start slinging shit about it. Just remember that nothing is worse than making CSS IE6 compatible.
4. Use [code] tags to format code blocks. |
On March 16 2012 22:47 Manit0u wrote:
#include <iostream>
using namespace std;
void displayGraph(int map[6][6]);
int main()
{
int map[6][6] =
{
{1, 1, 1, 1, 1, 1},
{1, 0, 0, 0, 0, 1},
{1, 0, 0, 0, 0, 1},
{1, 0, 0, 0, 0, 1},
{1, 0, 0, 0, 0, 1},
{1, 1, 1, 1, 1, 1}
};
displayGraph(map);
system("PAUSE");
return 0;
}
void displayGraph(int map[6][6])
{
for (int x = 0; x < 7; x++)
{
for (int y = 0; y < 7; y++)
{
if (map[x][y] == 1)
{
cout << "#";
}
else if (map[x][y] == 0)
{
cout << " ";
}
}
}
return;
}
Cleared up the code (global variables are unnecessary here, used prototype for displayGraph function) and removed endlines. Experiment with it 
tiny hint: When your array has 6 entries, they are numerated 0 through 5. So your for-loops should be conditioned to x<6, not x<7 ;P same for y obviously.
/edit: also, for robustness, you should add a ' else {cout << "?";} ', otherwise your formatting breaks when values other than 1 and 0 occur. And i believe, a line break should be written after the inner for-loop.
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I didn't write that. I just cleared the formatting a bit.
And yeah, linebreak should be there.
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Alright, so I'm writing a User Interface for a touch-screen on a robot. The user will tap on a map where they want the robot to go, and it'll go. We've already got the robot capable of going anywhere on the map, and finding its way around. My problem is, the program to control the robot's motion is in C++, but the UI is being written in Java. Due to the complexity of the robot's operating system, writing both in a single C++ program is pretty much out of the question. The touch-screen drivers and the motors' drivers can't talk to each other very easily, so the program would have access to one or the other, but not both.
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this?
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On March 17 2012 05:07 Millitron wrote:
Alright, so I'm writing a User Interface for a touch-screen on a robot. The user will tap on a map where they want the robot to go, and it'll go. We've already got the robot capable of going anywhere on the map, and finding its way around. My problem is, the program to control the robot's motion is in C++, but the UI is being written in Java. Due to the complexity of the robot's operating system, writing both in a single C++ program is pretty much out of the question. The touch-screen drivers and the motors' drivers can't talk to each other very easily, so the program would have access to one or the other, but not both.
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this?
This is precisely what Google's Protocol Buffers was designed for, you can define your messages and then instantiate them on either side, fill in the data, then just push it through a socket and deserialize on the other side.
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On March 17 2012 05:07 Millitron wrote:
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this?
There's something called JNI (but that doesn't start a separate process, it lets you call native code from within JVM). Alternatively, you can use regular IPC or some library like the one suggested by b0lt.
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On March 17 2012 05:15 b0lt wrote:Show nested quote +On March 17 2012 05:07 Millitron wrote:
Alright, so I'm writing a User Interface for a touch-screen on a robot. The user will tap on a map where they want the robot to go, and it'll go. We've already got the robot capable of going anywhere on the map, and finding its way around. My problem is, the program to control the robot's motion is in C++, but the UI is being written in Java. Due to the complexity of the robot's operating system, writing both in a single C++ program is pretty much out of the question. The touch-screen drivers and the motors' drivers can't talk to each other very easily, so the program would have access to one or the other, but not both.
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this? This is precisely what Google's Protocol Buffers was designed for, you can define your messages and then instantiate them on either side, fill in the data, then just push it through a socket and deserialize on the other side.
Also worth looking into Java Native functionality. You can have some C++ functions declared in a header file (implemented elsewhere, ofc) and you can use java to call these C++ functions. Also worth looking into static and dynamic libraries (.lib and .dll). Best of luck on your inter-language integration! There are a thousand ways to accomplish what you are looking to do, but you only need one, so if you think one is too hard, move on to the next!
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On March 17 2012 05:15 b0lt wrote:Show nested quote +On March 17 2012 05:07 Millitron wrote:
Alright, so I'm writing a User Interface for a touch-screen on a robot. The user will tap on a map where they want the robot to go, and it'll go. We've already got the robot capable of going anywhere on the map, and finding its way around. My problem is, the program to control the robot's motion is in C++, but the UI is being written in Java. Due to the complexity of the robot's operating system, writing both in a single C++ program is pretty much out of the question. The touch-screen drivers and the motors' drivers can't talk to each other very easily, so the program would have access to one or the other, but not both.
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this? This is precisely what Google's Protocol Buffers was designed for, you can define your messages and then instantiate them on either side, fill in the data, then just push it through a socket and deserialize on the other side.
This looks promising, but I still have a problem.
Is there a way to have only the Java program running until it gets input from the user, then have it start the C++ program and send it its necessary data? Because we'd like to include other functionality as well. For instance, the robot also has a little grabber arm it can move around. The grabber code is written in C++ too. We want the user to be able to access all the functionality from this one UI. Currently, you have to go through the file browser and manually start either the code for moving the robot itself, or the code for moving the arm. So if its possible, I'd like to not have all this stuff running at the same time, and instead only boot up the programs the user selects. The description of the Protocol Buffer makes it sound like I need both ends running at the same time.
On March 17 2012 05:28 RoyGBiv_13 wrote:Show nested quote +On March 17 2012 05:15 b0lt wrote:On March 17 2012 05:07 Millitron wrote:
Alright, so I'm writing a User Interface for a touch-screen on a robot. The user will tap on a map where they want the robot to go, and it'll go. We've already got the robot capable of going anywhere on the map, and finding its way around. My problem is, the program to control the robot's motion is in C++, but the UI is being written in Java. Due to the complexity of the robot's operating system, writing both in a single C++ program is pretty much out of the question. The touch-screen drivers and the motors' drivers can't talk to each other very easily, so the program would have access to one or the other, but not both.
What I'm wondering is, is it possible to start a C++ program and send it commands from within a Java program? How would I go about doing this? This is precisely what Google's Protocol Buffers was designed for, you can define your messages and then instantiate them on either side, fill in the data, then just push it through a socket and deserialize on the other side. Also worth looking into Java Native functionality. You can have some C++ functions declared in a header file (implemented elsewhere, ofc) and you can use java to call these C++ functions. Also worth looking into static and dynamic libraries (.lib and .dll). Best of luck on your inter-language integration! There are a thousand ways to accomplish what you are looking to do, but you only need one, so if you think one is too hard, move on to the next!
I'll check out these things too. And thanks, I think I'll need the luck 
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it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet.
that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant.
/edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html
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Hello everybody! I am currently working on small school project (just a small online library system), and in it you should be able to search for a book. Anyways, i wrote a SOL-Query (ViIsual Studios MYSQL) that looks like this:
+ Show Spoiler +SELECT bTitle,Bocker.bId,bPubliceringsAr,bGenre,ISBN,fFornamnNamn, fEfternamn, fPnr,fId,
FROM Bocker, Forfattare, bokForfattare
WHERE bTitle=@bokTitle AND Bocker.bId=bokForfattare.bId AND Forfattare.fId=bokForfattare.fId;
Some names in Swedish but its pretty straight forward. It gets a book title and some other stuff and also authors to the book, through a middle table since the book can have many authors.
Anyways, when i tested the query in VS i changed it automatically to this:
+ Show Spoiler +
SELECT bTitle, Bocker.bId, bPubliceringsAr, bGenre, ISBN, fFornamn, fEfternamn, fPnr, Forfattare.fId
FROM Bocker
INNER JOIN bokForfattare ON Bocker.bId = bokForfattare.bId
INNER JOIN Forfattare ON bokForfattare.fId = Forfattare.fId
WHERE (Bocker.bTitle = @bokTitle)
Now i understand this full and well, but my question is why it changed it. Is this method faster? putt less stress on the database? I can agree that it looks more proffesional, but is it better?
Love ♥
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On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html
I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it?
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aderum , what you want to google is implicit join vs explicit join.
The following is considered ANSI syntax:
SELECT bTitle, Bocker.bId, bPubliceringsAr, bGenre, ISBN, fFornamn, fEfternamn, fPnr, Forfattare.fId
FROM Bocker
INNER JOIN bokForfattare ON Bocker.bId = bokForfattare.bId
INNER JOIN Forfattare ON bokForfattare.fId = Forfattare.fId
WHERE (Bocker.bTitle = @bokTitle)
This version also has less predicates(# of where clauses) and is easier for debugging purposes.
The execution time for both are the same. Take a look at the execution plan to see what the both the queries are doing. They will have the same execution plan.
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On March 17 2012 08:23 Millitron wrote:Show nested quote +On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it?
Wouldn't it be possible to just re-write the touch screen GUI in C++? Having 2 different languages operating the same robot seems like a bitch to maintain and more trouble than actual help.
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On March 17 2012 08:39 Neshapotamus wrote:
aderum , what you want to google is implicit join vs explicit join.
The following is considered ANSI syntax:
SELECT bTitle, Bocker.bId, bPubliceringsAr, bGenre, ISBN, fFornamn, fEfternamn, fPnr, Forfattare.fId
FROM Bocker
INNER JOIN bokForfattare ON Bocker.bId = bokForfattare.bId
INNER JOIN Forfattare ON bokForfattare.fId = Forfattare.fId
WHERE (Bocker.bTitle = @bokTitle)
This version also has less predicates(# of where clauses) and is easier for debugging purposes.
The execution time for both are the same. Take a look at the execution plan to see what the both the queries are doing. They will have the same execution plan.
Okay great, reading about it right now (remember reading about it when i started to learn SQL...)
Thank you kind sir =)
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About to start a project - school admin system (grades, library, personnel, finance modules + other possible stuff like forum). Will be a ruby on rails app and I have plans to monetize it in the future (there's a dire need for good school admin systems here in Mexico). If anyone is interested in participating, pm me, some knowledge of ruby/rails is a bonus, willingness to work is preferable. This sounds like a job offer but it isn't, just an open source project where you can participate. And it can instead become a programming/ruby/rails study group.
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On March 17 2012 08:23 Millitron wrote:Show nested quote +On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it?
a programs stdin, stdout and stderr are all pipes that can be redirected to whatever in any operating system. For instance, you can write two programs that only use stdin and stdout, and then "connect" them by calling "programA | programB" on your command line.
For instance, you can build processing chains like "ls all file names", "grep all file names whose regexp matches X", "delete all matched files" by building a chain with "ls -parameters > grep regexp > del" or something like this. > is a one-way-pipe redirecting stdout, | is a both way pipe connecting stdin and stdout forward an backwards i believe. You can also redirect stderr through >&2 or something weird like that, google up on that if you really want to know. You can even redirect stdout and stderr to a file (./program > stdout.txt), or append to a file (./program >> stdout.txt) or even us a file as stdin (./program < stdin.txt).
This all works without using any special language features, every program just needs to use its stdin and stdout. The operating system can already redirect those however it likes.
Anyhow, when invoking a process from within java (and other languages certainly offer equal features), of course you can read and write from these pipes, too. To obtain a pipe to the programs stdin in java, do something like this:
Process process = Runtime.getRuntime().exec("command") ;
PrintWriter toProgram = new PrintWriter(process.getOutputStream());
toProgram.println("drive left!");
toProgram.println("drive straight!");
the effect is the same as when you usually would type into the programs console.
Similarly you can obtain the programs stdout as process.getInputStream() and stderr as process.getErrorStream(), and then read from those. Wrap in BufferedReaders for automatic .readLine() and the likes, use it just the same as when reading from a FileInputStream. Read up on what you can do with these process objects here: http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html
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On March 17 2012 08:53 Manit0u wrote:Show nested quote +On March 17 2012 08:23 Millitron wrote:On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it? Wouldn't it be possible to just re-write the touch screen GUI in C++? Having 2 different languages operating the same robot seems like a bitch to maintain and more trouble than actual help.
The biggest advantage for us using Java for the GUI is that we can test it on any computer, not just the robot. We could write the GUI in C++ I suppose, but to be able to test it on a normal PC, it would have to be completely separate from the robot's code anyways. Because of the file structure and operating system on the robot, it is pretty difficult to install stuff to it. If it was written directly into the robot's code, it would have to be compiled and re-installed every time we made a change, which would be a huge pain. So this means we pretty much need two programs anyways, 1 for the GUI, one for the robot's motion. And if we already need two programs, we may as well have the GUI in Java, so when I graduate, other students at my school can easily pick up where I left off, since Java is taught freshman year.
On March 17 2012 09:32 MisterD wrote:Show nested quote +On March 17 2012 08:23 Millitron wrote:On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it? a programs stdin, stdout and stderr are all pipes that can be redirected to whatever in any operating system. For instance, you can write two programs that only use stdin and stdout, and then "connect" them by calling "programA | programB" on your command line. For instance, you can build processing chains like "ls all file names", "grep all file names whose regexp matches X", "delete all matched files" by building a chain with "ls -parameters > grep regexp > del" or something like this. > is a one-way-pipe redirecting stdout, | is a both way pipe connecting stdin and stdout forward an backwards i believe. You can also redirect stderr through >&2 or something weird like that, google up on that if you really want to know. You can even redirect stdout and stderr to a file (./program > stdout.txt), or append to a file (./program >> stdout.txt) or even us a file as stdin (./program < stdin.txt). This all works without using any special language features, every program just needs to use its stdin and stdout. The operating system can already redirect those however it likes. Anyhow, when invoking a process from within java (and other languages certainly offer equal features), of course you can read and write from these pipes, too. To obtain a pipe to the programs stdin in java, do something like this: Process process = Runtime.getRuntime().exec("command") ; PrintWriter toProgram = new PrintWriter(process.getOutputStream()); toProgram.println("drive left!"); toProgram.println("drive straight!"); the effect is the same as when you usually would type into the programs console. Similarly you can obtain the programs stdout as process.getInputStream() and stderr as process.getErrorStream(), and then read from those. Wrap in BufferedReaders for automatic .readLine() and the likes, use it just the same as when reading from a FileInputStream. Read up on what you can do with these process objects here: http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html
Oh man, the Process class is so cool. I wish I knew about it sooner. It's just so elegant.
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So here's my question...
I have absolutely no knowledge of how to program, none, and I am moving into Computer Sciences at UNB this fall and I'm curious if anyone can give me the possibility to enter into programming in a manner that its not a huge steep learning curve... I know a lot about computers, but just nothing about the process of programming them : ( Anyone help? Just general tips would be nice
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On March 18 2012 09:16 NeMeSiS3 wrote:
So here's my question...
I have absolutely no knowledge of how to program, none, and I am moving into Computer Sciences at UNB this fall and I'm curious if anyone can give me the possibility to enter into programming in a manner that its not a huge steep learning curve... I know a lot about computers, but just nothing about the process of programming them : ( Anyone help? Just general tips would be nice
Try this: http://cecilsunkure.blogspot.com/2011/02/i-want-to-learn-programming-but-i-know.html
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On March 17 2012 14:29 Millitron wrote:Show nested quote +On March 17 2012 08:53 Manit0u wrote:On March 17 2012 08:23 Millitron wrote:On March 17 2012 05:47 MisterD wrote:it boils down to either making your robot stuff a .dll (or linux equivalent) and using it with a native interface in java, or writing a c++ standalone host application that gets sent commands via network sockets. The latter is certainly more work, as you have to write a proper network handler in c++ in addition to the java client, but on the other hand allows you to easily write a lot more clients and implement remote-control through lan/wlan/internet. that google proto stuff that someone linked seems to be just a marshalling format, i suppose this would help in the socket approach as you can just create java and c++ stucts for your data objects which both use the same marshalling format, so you can easily flatten data into a network stream and reconstruct it at the other end. So if you go this way, that might be helpful. for direct method invocation through native interfaces, it's probably rather irrelevant. /edit: java can start other programs, have a look at http://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html I'm looking into the Runtime API, and I'm wondering, can the output stream of the runtime object act as the console for the C++ program? So instead of dealing with native interfaces or networking, I could just have the C++ program read the instructions from the console? I'm thinking that from the C++ program's point of view, a console is a console, it doesn't really care what fills in the prompts on the console, does it? Wouldn't it be possible to just re-write the touch screen GUI in C++? Having 2 different languages operating the same robot seems like a bitch to maintain and more trouble than actual help. The biggest advantage for us using Java for the GUI is that we can test it on any computer, not just the robot. We could write the GUI in C++ I suppose, but to be able to test it on a normal PC, it would have to be completely separate from the robot's code anyways. Because of the file structure and operating system on the robot, it is pretty difficult to install stuff to it. If it was written directly into the robot's code, it would have to be compiled and re-installed every time we made a change, which would be a huge pain. So this means we pretty much need two programs anyways, 1 for the GUI, one for the robot's motion. And if we already need two programs, we may as well have the GUI in Java, so when I graduate, other students at my school can easily pick up where I left off, since Java is taught freshman year.
Well, if you have stuff in C++ in the robot OS, I hardly see a problem. Especially that GUI like wxWidgets (which I'm just getting into) is platform-independent and pretty damn neat.
http://www.wxwidgets.org/
From the 'about':
wxWidgets is a C++ library that lets developers create applications for Windows, OS X, Linux and UNIX on 32-bit and 64-bit architectures as well as several mobile platforms including Windows Mobile, iPhone SDK and embedded GTK+. It has popular language bindings for Python, Perl, Ruby and many other languages. Unlike other cross-platform toolkits, wxWidgets gives its applications a truly native look and feel because it uses the platform's native API rather than emulating the GUI. It's also extensive, free, open-source and mature.
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EPT
