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• Text message intent - catch and send

  - by Espen

  Hi! I want to be able to control incoming text messages. My application is still on a "proof of concept" version and I'm trying to learn Android programming as I go. First my application need to catch incomming text messages. And if the message is from a known number then deal with it. If not, then send the message as nothing has happened to the default text message application. I have no doubt it can be done, but I still have some concern and I see some pitfalls at how things are done on Android. So getting the incomming text message could be fairly easy - except when there are other messaging applications installed and maybe the user wants to have normal text messages to pop up on one of them - and it will, after my application has had a look at it first. How to be sure my application get first pick of incomming text messages? And after that I need to send most text messages through to any other text message application the user has chosen so the user can actually read the message my application didn't need. Since Android uses intents that are relative at best, I don't see how I can enforce my application to get a peek at all incomming text messages, and then stop it or send it through to the default text messaging application...

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• when an autoreleased object is actually released?

  - by psebos

  Hi, I am new in objective-c and I am trying to understand memory management to get it right. After reading the excellent Memory Management Programming Guide for Cocoa by apple my only concern is when actually an autoreleased object is released in an iphone/ipod application. My understanding is at the end of a run loop. But what defines a run loop in the application? So I was wondering whether the following piece of code is right. Assume an object @implementation Test - (NSString *) functionA { NSString *stringA; stringA = [[NSString alloc] initWithString:@"Hello" autorelease] return stringA; } - (NSString *) functionB { NSString *stringB; stringB = [self functionA]; return stringB; } - (NSString *) functionC { NSString *stringC; stringC = [self functionB]; return stringC; } - (void)viewDidLoad { [super viewDidLoad]; (NSString *) p = [self functionC]; NSLog(@"string is %@",p); } @end Is this code valid? From the apple text I understand that the NSString returned from functionA is valid in the scope of functionB. I am not sure whether it is valid in functionC and in viewDidLoad. Thanks!

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• Using JavaCC to infer semantics from a Composite tree

  - by Skice

  Hi all, I am programming (in Java) a very limited symbolic calculus library that manages polynomials, exponentials and expolinomials (sums of elements like "x^n * e^(c x)"). I want the library to be extensible in the sense of new analytic forms (trigonometric, etc.) or new kinds of operations (logarithm, domain transformations, etc.), so a Composite pattern that represent the syntactic structure of an expression, together with a bunch of Visitors for the operations, does the job quite well. My problem arise when I try to implement operations that depends on the semantics more than on the syntax of the Expression (like integrals, for instance: there are a lot of resolution methods for specific classes of functions, but these same classes can be represented with more than a single syntax). So I thought I need something to "parse" the Composite tree to infer its semantics in order to invoke the right integration method (if any). Someone pointed me to JavaCC, but all the examples I've seen deal only with string parsing; so, I don't know if I'm digging in the right direction. Some suggestions? (I hope to have been clear enough!)

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• FILE* issue PPU side code

  - by Cristina

  We are working on a homework on CELL programming for college and their feedback response to our questions is kinda slow, thought i can get some faster answers here. I have a PPU side code which tries to open a file passed down through char* argv[], however this doesn't work it cannot make the assignment of the pointer, i get a NULL. Now my first idea was that the file isn't in the correct directory and i copied in every possible and logical place, my second idea is that maybe the PPU wants this pointer in its LS area, but i can't deduce if that's the bug or not. So... My question is what am i doing wrong? I am working with a Fedora 7 SDK Cell, with Eclipse as an IDE. Maybe my argument setup is wrong tho he gets the name of the file correctly. Code on request: images_t *read_bin_data(char *name) { FILE *file; images_t *img; uint32_t *buffer; uint8_t buf; unsigned long fileLen; unsigned long i; //Open file file = (FILE*)malloc(sizeof(FILE)); file = fopen(name, "rb"); printf("[Debug]Opening file %s\n",name); if (!file) { fprintf(stderr, "Unable to open file %s", name); return NULL; } //....... } Main launch: int main(int argc,char* argv[]) { int i,img_width; int modif_this[4] __attribute__ ((aligned(16))) = {1,2,3,4}; images_t *faces, *nonfaces; spe_context_ptr_t ctxs[SPU_THREADS]; pthread_t threads[SPU_THREADS]; thread_arg_t arg[SPU_THREADS]; //intializare img_width img_width = atoi(argv[1]); printf("[Debug]Img size is %i\n",img_width); faces = read_bin_data(argv[3]); //....... } Thanks for the help.

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• function objects versus function pointers

  - by kumar_m_kiran

  Hi All, I have two questions related to function objects and function pointers, Question : 1 When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example class State { public: //... int population() const; float aveTempF() const; //... }; struct PopLess : public std::binary_function<State,State,bool> { bool operator ()( const State &a, const State &b ) const { return popLess( a, b ); } }; sort( union, union+50, PopLess() ); Question : Now, How does the statement, sort(union, union+50,PopLess()) work? PopLess() must be resolved into something like PopLess tempObject.operator() which would be same as executing the operator () function on a temporary object. I see this as, passing the return value of overloaded operation i.e bool (as in my example) to sort algorithm. So then, How does sort function resolve the third parameter in this case? Question : 2 Question Do we derive any particular advantage of using function objects versus function pointer? If we use below function pointer will it derive any disavantage? inline bool popLess( const State &a, const State &b ) { return a.population() < b.population(); } std::sort( union, union+50, popLess ); // sort by population PS : Both the above references(including example) are from book "C++ Common Knowledge: Essential Intermediate Programming" by "Stephen C. Dewhurst". I was unable to decode the topic content, thus have posted for help. Thanks in advance for your help.

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• Get a "sqlceqp35.dll" error when debugging but not when running deployed code.

  - by nj

  In our current windows mobile project a problem while debugging recently arised. When trying to debug the code it throws an exception on the open command on a connection to the local database. The message is "A SQL Server Compact DLL could not be loaded. Reinstall SQL Server Compact Edition. [ DLL Name = sqlceqp35.dll ]". Sometime it's an unknow error instead, with reference to the same file. If you execute the binary, thats deployd during the debug, on the device it runs without any problem. I've tried: Reinstall both .net and sqlce on the device. Changed the "specific version" on the reference properties in the project. The hardware I'm using is a Motorola MC70 with Windows mobile 5.0. The target platform of the project is windows mobile 5.0. Any ideas on what might cause this problem? EDIT: When I tried it on a MC75 I can debug it. The MC70 got OS Version: 05.01.0478 and the MC75 05.01.0478. My best guess now is that it's someway related to the OS version or the actual device.

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• How to draw some lines in a view element defined in the xml layout

  - by Nils

  Hello, I have problems drawing some simple lines in a view object (Android programming). First I created the layout with the view element(kind of painting area) in it (XML file). [...] < View android:id="@+id/viewmap" android:layout_width="572px" android:layout_height="359px" android:layout_x="26px" android:layout_y="27px" [...] ... and tried then to access it to draw some lines. Unfortunately the program is running and other UI elements like buttons are displayed, but I can't see the drawings. What's wrong ? [...] viewmap = (View) findViewById(R.id.viewmap); Canvas canvas = new Canvas(); viewmap.draw(canvas); Paint p = new Paint(); p.setColor(Color.BLUE); p.setStyle(Paint.Style.STROKE); canvas.drawColor(Color.WHITE); p.setColor(Color.BLUE); canvas.drawLine(4, 4, 29, 5, p); p.setColor(Color.RED); viewmap.draw(canvas); [...] Thanks for help :) !

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• How do I track down sporadic ASP.NET performance problems in a production environment?

  - by Steve Wortham

  I've had sporadic performance problems with my website for awhile now. 90% of the time the site is very fast. But occasionally it is just really, really slow. I mean like 5-10 seconds load time kind of slow. I thought I had narrowed it down to the server I was on so I migrated everything to a new dedicated server from a completely different web hosting company. But the problems continue. I guess what I'm looking for is a good tool that'll help me track down the problem, because it's clearly not the hardware. I'd like to be able to log certain events in my ASP.NET code and have that same logger also track server performance/resources at the time. If I can then look back at the logs then I can see what exactly my website was doing at the time of extreme slowness. Is there a .NET logging system that'll allow me to make calls into it with code while simultaneously tracking performance? What would you recommend?

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• What are the alternatives to public fields?

  - by James

  I am programming a game in java, and as the question title suggestions i am using public fields in my classes. (for the time being) From what i have seen public fields are bad and i have some understanding why. (but if someone could clarify why you should not use them, that would be appreciated) The thing is that also from what i have seen, (and it seems logical) is that using private fields, but using getters and setters to access them is also not good as it defeats the point of using private fields in the first place. So, my question is, what are the alternatives? or do i really have to use private fields with getters and setters? For reference here is one of my classes, and some of its methods. I will elaborate more if needs be. //The player's fields. public double health; public String name; public double goldCount; public double maxWeight; public double currentWeight; public double maxBackPckSlts; public double usedBackPckSlts; // The current back pack slots in use public double maxHealth; // Maximum amount of health public ArrayList<String> backPack = new ArrayList<String>(); //This method happens when ever the player dynamically takes damage(i.e. when it is not scripted for the player to take damage. //Parameters will be added to make it dynamic so the player can take any spread of damage. public void beDamaged(double damage) { this.health -= damage; if (this.health < 0) { this.health = 0; } } public void gainHealth(double gainedHp) { this.health += gainedHp; if (this.health > this.maxHealth) { this.health = this.maxHealth; } }

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• Is Form validation and Business validation too much?

  - by Robert Cabri

  I've got this question about form validation and business validation. I see a lot of frameworks that use some sort of form validation library. You submit some values and the library validates the values from the form. If not ok it will show some errors on you screen. If all goes to plan the values will be set into domain objects. Here the values will be or, better said, should validated (again). Most likely the same validation in the validation library. I know 2 PHP frameworks having this kind of construction Zend/Kohana. When I look at programming and some principles like Don't Repeat Yourself (DRY) and single responsibility principle (SRP) this isn't a good way. As you can see it validates twice. Why not create domain objects that do the actual validation. Example: Form with username and email form is submitted. Values of the username field and the email field will be populated in 2 different Domain objects: Username and Email class Username {} class Email {} These objects validate their data and if not valid throw an exception. Do you agree? What do you think about this aproach? Is there a better way to implement validations? I'm confused about a lot of frameworks/developers handling this stuff. Are they all wrong or am I missing a point? Edit: I know there should also be client side kind of validation. This is a different ballgame in my Opinion. If You have some comments on this and a way to deal with this kind of stuff, please provide.

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• Why does this data YYYY-MM-DD regex fail in Java?

  - by ProfessionalAmateur

  Hello StackOverFlow, My first question and Im excited... I've lurked since go-live and love the site, however I apologize for any newbie errors, formatting, etc... I'm attempting to validate the format of a string field that contains a date in Java. We will receive the date in a string, I will validate its format before parsing it into a real Date object. The format being passed in is in the YYYY-MM-DD format. However I'm stuck on one of my tests, if I pass in "1999-12-33" the test will fail (as it should with a day number 33) with this incomplete pattern: ((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-([12][0-9]|3[01]) However as soon as I add the characters in bold below it passes the test (but should not) ((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-(0[1-9]|[1-9]|[12][0-9]|3[01]) *additional note, I know I can change the 0[1-9]|[1-9] into 0?[1-9] but I wanted to break everything down to its most simple format to try and find why this isn't working. Here is the scrap test I've put together to run through all the different date scenarios: import java.util.regex.Matcher; import java.util.regex.Pattern; public class scrapTest { public scrapTest() { } public static void main(String[] args) { scrapTest a = new scrapTest(); boolean flag = a.verfiyDateFormat("1999-12-33"); } private boolean verfiyDateFormat(String dateStr){ Pattern datePattern = Pattern.compile("((19|20)\\d{2})-([1-9]|0[1-9]|1[0-2])-(0[1-9]|[1-9]|[12][0-9]|3[01])"); Matcher dateMatcher = datePattern.matcher(dateStr); if(!dateMatcher.find()){ System.out.println("Invalid date format!!! -> " + dateStr); return false; } System.out.println("Valid date format."); return true; } } Ive been programming for ~10 years but extremely new to Java, so please feel free to explain anything as elementary as you see fit.

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• super light software development process

  - by Walty

  hi, For the development process I have involved so far, most have teams of SINGLE member, or occasionally two. We used python + django for the major development, the development process is actually very fast, and we do have code reviews, design pattern discussions, and constant refactoring. Though team size is small, I do think there are some development processes / best practices that could be enforced. For example, using svn would be definitely better than regular copy backup. I did read some articles & books about Agile, XP & continuous integration, I think they are nice, but still too heavy for this case (team of 1 or 2, and fast coding). For example, IMHO, with nice design pattern, and iterative development + refactoring, the TDD MIGHT be an overkill, or at least the overhead does not out-weight the advantages. And so is the pair programming. The automated testing is a nice idea, but it seems not technically feasible for every project. our current practices are: svn + milestone + code review I wonder if there are development processes / best practices specifically targeted on such super light teams? thanks.

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• Need guidelines for optimizing WebGL performance by minimizing shader changes

  - by brainjam

  I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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• Are there any configurable parameters to the gpsd?

  - by danatel

  I use the gpsd daemon with my application. Sometimes, the gpsd ceases to work with no apparent reason (clean sky). Even the gpsmon monitor shows no fix. Are there any parameters which must be set? Or is it a hardware problem? I am surprissed that many satellites are visible but the "Stat" bitmap does not contain the bit 7 - ephemeris data available. Should i somewhat pre-configure my position to allow for correct ephemeris data? Here is my gpsmon screen: 127.0.0.1:2947:/dev/ttyS3 SiRF binary> ^[[4~ -¦¦¦¦¦¦¦¦¦¦¦ X ¦¦¦¦¦¦ Y ¦¦¦¦¦¦ Z ¦¦¦¦¦¦¦¦¦¦ North ¦¦¦¦ East ¦¦¦¦¦ Alt ¦¦¦¦¦¦¦¦¦¬ -Pos: 3949260 1166016 4856299 m 49.89411° 16.44920° 1379 m - -Vel: 0.0 0.0 0.0 m/s 0.0 0.0 0.0 climb m/s- -Week+TOW:1578+224837.06 Day: 2 14:27:17.06 Heading: 0.0° 0.0 speed m/s- -Skew: -13.025817 TZ: -7200 HDOP: 0.0 M1:00 M2: 00 - -Fix: 0 = - L¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ Packet type 2 (0x02) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬-¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ -Ch PRN Az El Stat C/N ? A --Version: - - 0 2 243 19 003f 40.4 -L¦¦¦¦¦¦¦ Packet Type 6 (0x06) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 1 10 249 68 003f 43.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 2 13 90 30 003f 40.9 --SVs: 0 Drift: 96506 Bias: 135976716 - - 3 7 66 67 003f 39.8 --Estimated GPS Time: 224837059 - - 4 5 295 49 003d 39.7 -L¦¦¦¦¦¦¦ Packet type 7 (0x07) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 5 8 210 69 003f 41.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 6 23 96 5 002d 28.0 --Max: 167.570Lat: 132.129Time: 0.075 MS: 02 - - 7 6 43 3 002d 23.1 -L¦¦¦¦¦¦¦ Packet type 9 (0x09) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 8 28 163 16 003f 39.8 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 9 0 0 0 0000 0.0 --SVs: 11 = 8 10 7 5 13 2 28 23 3 6 4 - -10 3 55 4 002d 24.7 -L¦¦¦¦¦¦¦ Packet type 13 (0x0D) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -11 0 0 0 0000 0.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ L¦¦¦ Packet Type 4 (0x04) ¦¦¦--DGPS source: 1 (SBAS) Corrections: 12 - L¦¦¦¦¦¦¦ Packet type 27 (0x1B) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦-q

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• Python and Unicode: How everything should be Unicode

  - by A A

  Forgive if this a long a question: I have been programming in Python for around six months. Self taught, starting with the Python tutorial and then SO and then just using Google for stuff. Here is the sad part: No one told me all strings should be Unicode. No, I am not lying or making this up, but where does the tutorial mention it? And most examples also I see just make use of byte strings, instead of Unicode strings. I was just browsing and came across this question on SO, which says how every string in Python should be a Unicode string. This pretty much made me cry! I read that every string in Python 3.0 is Unicode by default, so my questions are for 2.x: Should I do a: print u'Some text' or just print 'Text' ? Everything should be Unicode, does this mean, like say I have a tuple: t = ('First', 'Second'), it should be t = (u'First', u'Second')? I read that I can do a from __future__ import unicode_literals and then every string will be a Unicode string, but should I do this inside a container also? When reading/ writing to a file, I should use the codecs module. Right? Or should I just use the standard way or reading/ writing and encode or decode where required? If I get the string from say raw_input(), should I convert that to Unicode also? What is the common approach to handling all of the above issues in 2.x? The from __future__ import unicode_literals statement? Sorry for being a such a noob, but this changes what I have been doing for a long time and so clearly I am confused.

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• SQLite for personal use

  - by ALife

  What are the applications for your personal use that needs a small database like SQLite? I am thinking of trying a few popular databases and SQLite is surely the first one I am planning to try since I know barely nothing about database except some simple programming years ago. I learned that SQLite is good for personal use. But embarrassingly I do not see any application except maybe managing my list of phone numbers/contact info, which has probably a few hundred items. What's your experience? FYI, I use EndNote for my reference and softcopy of books, and I feel iTunes' music/media management is ok since I am not a frequent user anyway. And others? I do lots of coding, but I just use some simple etags tools for that. And I pretty much use .txt file (sometimes in the asciidoc style) for my notes. I have quite a bunch of notes, but not that many either. So, really, what are your personal applications that need a small database instead of existing tools and plain text files?

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• Given 4 objects, how to figure out whether exactly 2 have a certain property

  - by Cocorico

  Hi guys! I have another question on how to make most elegant solution to this problem, since I cannot afford to go to computer school right so my actual "pure programming" CS knowledge is not perfect or great. This is basically an algorhythm problem (someone please correct me if I am using that wrong, since I don't want to keep saying them and embarass myself) I have 4 objects. Each of them has an species property that can either be a dog, cat, pig or monkey. So a sample situation could be: object1.species=pig object2.species=cat object3.species=pig object4.species=dog Now, if I want to figure out if all 4 are the same species, I know I could just say: if ( (object1.species==object2.species) && (object2.species==object3.species) && (object3.species==object4.species) ) { // They are all the same animal (don't care WHICH animal they are) } But that isn't so elegant right? And if I suddenly want to know if EXACTLY 3 or 2 of them are the same species (don't care WHICH species it is though), suddenly I'm in spaghetti code. I am using Objective C although I don't know if that matters really, since the most elegant solution to this is I assume the same in all languages conceptually? Anyone got good idea? Thanks!!

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• Using GCC (MinGW) to compile OpenGL on Windows

  - by Casey

  I've searched on google and haven't been able to come up with a solution. I would like to compile some OpenGL programming using GCC. In the GL folder in GCC I have the following headers: gl.h glext.h glu.h Then in my system32 file I have the following .dll opengl32.dll glu32.dll glut32.dll If I wanted to write a simple OpenGL "Hello World" and link and compile with GCC, what is the correct process? I'm attempting to use this code: #include <GL/gl.h> #include <GL/glut.h> void display() { glClear(GL_COLOR_BUFFER_BIT); glFlush(); } int main(int argc, char **argv) { glutInit(&argc, argv); glutInitWindowSize(512,512); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutCreateWindow("The glut hello world program"); glutDisplayFunc(display); glClearColor(0.0, 0.0, 0.0, 1.0); glutMainLoop(); // Infinite event loop return 0; } Thank you in advance for the help.

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• Can't Display Bitmap of Higher Resolution than CDC area

  - by T. Jones

  Hi there dear gurus and expert coders. i am not gonna start with im a newbie and don't know much about image programming but unfortunately those are the facts :( I am trying to display an image from a bitmap pointer *ImageData which is of resolution 1392x1032. I am trying to draw that at an area of resolution or size 627x474. However, repeated trying doesnt seem to work. It works when I change the bitmap image I created from *ImageData width and height to resolution or size of around 627x474 I really do not know how to solve this after trying all possible solutions from various forums and google. pDC is a CDC* and memDC is a CDC initialized in an earlier method Anything uninitialized here was initialized in other methods. Here is my code dear humble gurus. Do provide me with guidance Yoda and Obi-Wan provided to Luke Skywalker. void DemoControl::ShowImage( void *ImageData ) { int Width; //Width of Image From Camera int Height; //Height of Image From Camera int m_DisplayWidth = 627 ;//width of rectangle area to display int m_DisplayHeight = 474;//height of rectangle area to display GetImageSize( &Width, &Height ) ; //this will return Width = 1392, Height 1032 CBitmap bitmap; bitmap.CreateBitmap(Width,Height,32,1,ImageData); CBitmap* pOldBitmap = memDC.SelectObject((CBitmap*)&bitmap); pDC->BitBlt(22, 24, 627, 474, &memDC, 0, 0, SRCCOPY); memDC.SelectObject((CBitmap*)pOldBitmap); ReleaseDC(pDC); }

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• Does Perl auto-vivify variables used as references in subroutine calls?

  - by FM

  I've declared 2010 to be the year of higher-order programming, so I'm learning Haskell. The introduction has a slick quick-sort demo, and I thought, "Hey, that's easy to do in Perl". It turned to be easier than I expected. Note that I don't have to worry about whether my partitions ($less and $more) are defined. Normally you can't use an undefined value as an array reference. use strict; use warnings; use List::MoreUtils qw(part); my @data = (5,6,7,4,2,9,10,9,5,1); my @sorted = qsort(@data); print "@sorted\n"; sub qsort { return unless @_; my $pivot = shift @_; my ($less, $more) = part { $_ < $pivot ? 0 : 1 } @_; # Works, even though $less and $more are sometimes undefined. return qsort(@$less), $pivot, qsort(@$more); } As best I can tell, Perl will auto-vivify a variable that you try to use as a reference -- but only if you are passing it to a subroutine. For example, my call to foo() works, but not the attempted print. use Data::Dumper qw(Dumper); sub foo { print "Running foo(@_)\n" } my ($x); print Dumper($x); # Fatal: Can't use an undefined value as an ARRAY reference. # print @$x, "\n"; # But this works. foo(@$x); # Auto-vivification: $x is now []. print Dumper($x); My questions: Am I understanding this behavior correctly? What is the explanation or reasoning behind why Perl does this? Is this behavior explained anywhere in the docs?

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• FIFO dequeueing in python?

  - by Aaron Ramsey

  hello again everybody— I'm looking to make a functional (not necessarily optimally efficient, as I'm very new to programming) FIFO queue, and am having trouble with my dequeueing. My code looks like this: class QueueNode: def __init__(self, data): self.data = data self.next = None def __str__(self): return str(self.data) class Queue: def__init__(self): self.front = None self.rear = None self.size = 0 def enqueue(self, item) newnode = QueueNode(item) newnode.next = None if self.size == 0: self.front = self.rear = newnode else: self.rear = newnode self.rear.next = newnode.next self.size = self.size+1 def dequeue(self) dequeued = self.front.data del self.front self.size = self.size-1 if self.size == 0: self.rear = None print self.front #for testing if I do this, and dequeue an item, I get the error "AttributeError: Queue instance has no attribute 'front'." I guess my function doesn't properly assign the new front of the queue? I'm not sure how to fix it though. I don't really want to start from scratch, so if there's a tweak to my code that would work, I'd prefer that—I'm not trying to minimize runtime so much as just get a feel for classes and things of that nature. Thanks in advance for any help, you guys are the best.

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• Systems design question: DB connection management in load-balanced n-tier

  - by aoven

  I'm wondering about the best approach to designing a DB connection manager for a load-balanced n-tier system. Classic n-tier looks like this: Client -> BusinessServer -> DBServer A load-balancing solution as I see it would then look like this: +--> ... +--+ +--> BusinessServer +--+--> SessionServer --+ Client -> Gateway --+--> BusinessServer +--| +--> DBServer +--> BusinessServer +--+--------------------+ +--> ... +--+ As pictured, the business server component is being load-balanced via multiple instances, and a hardware gateway is distributing the load among them. Session server probably needs to be situated outside the load-balancing array, because it manages state, which mustn't be duplicated. Barring any major errors in design so far, what is the best way to implement DB connection management? I've come up with a couple of options, but there may be others I'm not aware of: Introduce a new Broker component between the DBServer and the other components and let it handle the DB connections. The upside is that all the connections can be managed from a single point, which is very convenient. The downside is that now there is an additional "single point of failure" in the system. Other components must go through it for every request that involves DB in some way, which also makes this a bottleneck. Move the DB connection management into BusinessServer and SessionServer components and let each handle its own DB connections. The upside is that there is no additional "single point of failure" or bottleneck components. The downside is that there is also no control over possible conflicts and deadlocks apart from what DBServer itself can provide. What else can be done? FWIW: Technology is .NET, but none of the vendor-specific stacks are used (e.g. no WCF, MSMQ or the like).

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• Automatic testing of GUI related private methods

  - by Stein G. Strindhaug

  When it comes to GUI programming (at least for web) I feel that often the only thing that would be useful to unit test is some of the private methods*. While unit testing makes perfect sense for back-end code, I feel it doesn't quite fit the GUI classes. What is the best way to add automatic testing of these? * Why I think the only methods useful to test is private: Often when I write GUI classes they don't even have any public methods except for the constructor. The public methods if any is trivial, and the constructor does most of the job calling private methods. They receive some data from server does a lot of trivial output and feeds data to the constructor of other classes contained inside it, adding listeners that calls a (more or less directly) calls the server... Most of it pretty trivial (the hardest part is the layout: css, IE, etc.) but sometimes I create some private method that does some advanced tricks, which I definitely do not want to be publicly visible (because it's closely coupled to the implementation of the layout, and likely to change), but is sufficiently complicated to break. These are often only called by the constructor or repeatedly by events in the code, not by any public methods at all. I'd like to have a way to test this type of methods, without making it public or resorting to reflection trickery. (BTW: I'm currently using GWT, but I feel this applies to most languages/frameworks I've used when coding for GUI)

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• I want my logs sent to my mail with logrotate

  - by lericson

  Not strictly a question about programming as such, more of a log handling question. Anyway. My company has multiple clients, and each of these clients have a set of logs that I'd rather much want to get sent to by e-mail to me. Now, another prerequisite is that they're hilighted by simple HTML. All that is very well, I've managed to make a hilighter for the given log types. So, what I do is I use logrotate's prerotate stuff to send the logs as an e-mail message. Example: /var/log/a.log /var/log/b.log { daily missingok copytruncate prerotate /usr/bin/python /home/foo/hilight_logs /var/log/{a,b}.log | /usr/sbin/sendmail -FLog\ mailer [email protected] [email protected] endscript } The problem with this approach is basically that logrotate sucks: it'll run the command for every log file specified in the specifier, and to my knowledge there's no way to know which of the log files is being handled. (Which wouldn't really help anyway.) Short of repeating the exact same logrotate up to 10 times on different machines, the only thing I can do is just to get bogged down with log spam every night. And I grew tired of it today, so I ask.

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• ASP.NET retrieve Average CPU Usage

  - by Sam

  Last night I did a load test on a site. I found that one of my shared caches is a bottleneck. I'm using a ReaderWriterLockSlim to control the updates of the data. Unfortunately at one point there are ~200 requests trying to update the data at approximately the same time. This also coincided with CPU usage spikes. The data being updated is in the ASP.NET Cache. What I'd like to do is if the CPU usage is around 75%, I'd like to just skip the cache and hit the database on another machine. My problem is that I don't know how expensive it is to create a new performance counter to check the cpu usage. Also, if I would probably like the average cpu usage over the last 2 or 3 seconds. However, I can't sit there and calculate the cpu time as that would take longer than it's taking to update the cache currently. Is there an easy way to get the average CPU usage? Are there any drawbacks to this? I'm also considering totaling the wait count for the lock and then at a certain threshold switch over to the database. The concern I had with this approach would be that changing hardware might allow more locks with less of a strain on the system. And also finding the right balance for the threshold would be cumbersome and it doesn't take into account any other load on the machine. But it's a simple approach, and simple is 99% of the time better.

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