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  • trying to make a simple grid-class, non-lvalue in assignment

    - by Tyrfing
    I'm implementing a simple C++ grid class. One Function it should support is accessed through round brackets, so that I can access the elements by writing mygrid(0,0). I overloaded the () operator and i am getting the error message: "non-lvalue in assignment". what I want to be able to do: //main cGrid<cA*> grid(5, 5); grid(0,0) = new cA(); excerpt of my implementation of the grid class: template class cGrid { private: T* data; int mWidth; int mHeight; public: cGrid(int width, int height) : mWidth(width), mHeight(height) { data = new T[width*height]; } ~cGrid() { delete data; } T operator ()(int x, int y) { if (x >= 0 && x <= mWidth) { if (y >= 0 && y <= mHeight) { return data[x + y * mWidth]; } } } const T &operator ()(int x, int y) const { if (x >= 0 && x <= mWidth) { if (y >= 0 && y <= mHeight) { return data[x + y * mWidth]; } } } The rest of the code deals with the implementation of an iterator and should not be releveant.

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  • Efficient cron job utilizing Zend_Mail_Storage_Imap.

    - by fireeyedboy
    I'm new to the IMAP protocol and Zend_Mail_Storage and I'm writing a small php script for a cron job that should regularly poll an IMAP account and check for new messages, and send an e-mail if new messages have arrived. As you can imagine, I want to only poll the IMAP account for relevant messages, and I only want to send a new e-mail if new messages have arrived since the last polled new message. So I thought of keeping track of the last message I polled with some unique identifier for a message. But I'm a bit uncertain about whether the methods I want to utilize for this do what I expect them to do though. So my questions are: Does the iterator position of Zend_Mail_Storage_Imap actually resemble some IMAP unique identifier for messages, or is it simply only and internal position of Zend_Mail_Storage_Abstract? For instance, if I tell it to seek() to message 5 (which I stored from an earlier session) will it indeed seek to the appropriate message on the IMAP server, even if for instance messages have been deleted since last session? Would keeping track of this latest polled message id in a file suffice for a cron job that, say, polls the account every 5 or 10 minutes? Or is this too naive, and should I be using a database for instance. Or is there maybe a much easier way to keep track of such state with Zend_Mail_Storage_Abstract? Also, do I need to poll every IMAP folder? Or is everything accumulated when I poll INBOX? If you could shed some light on any of these matters, I'ld appreciate it. Thanks in advance.

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  • Range-based `for` statement definition redundancy

    - by GMan - Save the Unicorns
    Looking at n3092, in §6.5.4 we find the equivalency for a range-based for loop. It then goes on to say what __begin and __end are equal to. It differentiates between arrays and other types, and I find this redundant (aka, confusing). It says for arrays types that __begin and __end are what you expect: a pointer to the first and a pointer to one-past the end. Then for other types, __begin and __end are equal to begin(__range) and end(__range), with ADL. Namespace std is associated, in order to find the std::begin and std::end defined in <iterator>, §24.6.5. However, if we look at the definition of std::begin and std::end, they are both defined for arrays as well as container types. And the array versions do exactly the same as above: pointer to the first, pointer to one-past the end. Why is there a need to differentiate arrays from other types, when the definition given for other types would work just as well, finding std::begin and std::end? Some abridged quotes for convenience: §24.6.5 The range-based for statement — if _RangeT is an array type, begin-expr and end-expr are __range and __range + __bound, respectively, where __bound is the array bound. If _RangeT is an array of unknown size or an array of incomplete type, the program is ill-formed. — otherwise, begin-expr and end-expr are begin(_range) and end(_range), respectively, where begin and end are looked up with argument-dependent lookup (3.4.2). For the purposes of this name lookup, namespace std is an associated namespace. and §24.6.5 range access template T* begin(T (&array)[N]); Returns: array. template T* end(T (&array)[N]); Returns: array + N.

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  • Generate jpeg compressed Tiff using RGB colorspace (using Java + JAI)

    - by nOiSe gaTe
    I'm trying to make tiled pyramidal tiffs from master tiff images using Java (JAI 1.1.3 + imageIO). The problem is: I NEED to make tiff files compressed in jpeg with RGB photometric interpretation and no matter what I try, the image still faces YCbCr photometric interpretation. Note: if I change compression type (eg. LZW or Deflate) I can get RGB colorspace but, as I said, I need jpeg compression. Except this detail the tiled PTiff I create it's ok, so I think it's better to focus the attention on simple compression step (uncompressed tiff -- jpeg tiff) this may be a basic example (removing any check to make it more readable) // reading MASTER BufferedImage img = ImageIO.read(uncompressedTiff); ImageOutputStream ios=null; ImageWriter writer=null; ios = ImageIO.createImageOutputStream(outFile); Iterator <ImageWriter> writers = ImageIO.getImageWritersByFormatName("tiff"); writer = writers.next(); // saving and compression params writer.setOutput(ios); ImageWriteParam param = writer.getDefaultWriteParam(); param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); param.setCompressionType("JPEG"); param.setCompressionQuality(0.8f); param.setTilingMode(ImageWriteParam.MODE_EXPLICIT); param.setTiling(256, 256, 0, 0); IIOMetadata metadata = getWriteMD(writer, param); // writing writer.write(metadata, new IIOImage(img, null, metadata), param); in getWriteMD method: .... TIFFTag photoInterp = base.getTag(BaselineTIFFTagSet.TAG_PHOTOMETRIC_INTERPRETATION); TIFFField fieldPhotoInter = new TIFFField(photoInterp, BaselineTIFFTagSet.PHOTOMETRIC_INTERPRETATION_RGB); .... here is the full version of getWriteMD()

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  • error: expected constructor, destructor, or type conversion before '(' token

    - by jonathanasdf
    include/TestBullet.h:12: error: expected constructor, destructor, or type conver sion before '(' token I hate C++ error messages... lol ^^ Basically, I'm following what was written in this post to try to create a factory class for bullets so they can be instantiated from a string, which will be parsed from an xml file, because I don't want to have a function with a switch for all of the classes because that looks ugly. Here is my TestBullet.h: #pragma once #include "Bullet.h" #include "BulletFactory.h" class TestBullet : public Bullet { public: void init(BulletData& bulletData); void update(); }; REGISTER_BULLET(TestBullet); <-- line 12 And my BulletFactory.h: #pragma once #include <string> #include <map> #include "Bullet.h" #define REGISTER_BULLET(NAME) BulletFactory::reg<NAME>(#NAME) #define REGISTER_BULLET_ALT(NAME, CLASS) BulletFactory::reg<CLASS>(NAME) template<typename T> Bullet * create() { return new T; } struct BulletFactory { typedef std::map<std::string, Bullet*(*)()> bulletMapType; static bulletMapType map; static Bullet * createInstance(char* s) { std::string str(s); bulletMapType::iterator it = map.find(str); if(it == map.end()) return 0; return it->second(); } template<typename T> static void reg(std::string& s) { map.insert(std::make_pair(s, &create<T>)); } }; Thanks in advance.

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  • python 'with' statement

    - by Stephen
    Hi, I'm using Python 2.5. I'm trying to use this 'with' statement. from __future__ import with_statement a = [] with open('exampletxt.txt','r') as f: while True: a.append(f.next().strip().split()) print a The contents of 'exampletxt.txt' are simple: a b In this case, I get the error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/tmp/python-7036sVf.py", line 5, in <module> a.append(f.next().strip().split()) StopIteration And if I replace f.next() with f.read(), it seems to be caught in an infinite loop. I wonder if I have to write a decorator class that accepts the iterator object as an argument, and define an __exit__ method for it? I know it's more pythonic to use a for-loop for iterators, but I wanted to implement a while loop within a generator that's called by a for-loop... something like def g(f): while True: x = f.next() if test(x): a = x elif test(x): b = f.next() yield [a,x,b] a = [] with open(filename) as f: for x in g(f): a.append(x)

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  • How much of STL is too much?

    - by Darius Kucinskas
    I am using a lot of STL code with std::for_each, bind, and so on, but I noticed that sometimes STL usage is not good idea. For example if you have a std::vector and want to do one action on each item of the vector, your first idea is to use this: std::for_each(vec.begin(), vec.end(), Foo()) and it is elegant and ok, for a while. But then comes the first set of bug reports and you have to modify code. Now you should add parameter to call Foo(), so now it becomes: std::for_each(vec.begin(), vec.end(), std::bind2nd(Foo(), X)) but that is only temporary solution. Now the project is maturing and you understand business logic much better and you want to add new modifications to code. It is at this point that you realize that you should use old good: for(std::vector::iterator it = vec.begin(); it != vec.end(); ++it) Is this happening only to me? Do you recognise this kind of pattern in your code? Have you experience similar anti-patterns using STL?

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  • Listing serial (COM) ports on Windows?

    - by Eli Bendersky
    Hello, I'm looking for a robust way to list the available serial (COM) ports on a Windows machine. There's this post about using WMI, but I would like something less .NET specific - I want to get the list of ports in a Python or a C++ program, without .NET. I currently know of two other approaches: Reading the information in the HARDWARE\\DEVICEMAP\\SERIALCOMM registry key. This looks like a great option, but is it robust? I can't find a guarantee online or in MSDN that this registry cell indeed always holds the full list of available ports. Tryint to call CreateFile on COMN with N a number from 1 to something. This isn't good enough, because some COM ports aren't named COMN. For example, some virtual COM ports created are named CSNA0, CSNB0, and so on, so I wouldn't rely on this method. Any other methods/ideas/experience to share? Edit: by the way, here's a simple Python implementation of reading the port names from registry: import _winreg as winreg import itertools def enumerate_serial_ports(): """ Uses the Win32 registry to return a iterator of serial (COM) ports existing on this computer. """ path = 'HARDWARE\\DEVICEMAP\\SERIALCOMM' try: key = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, path) except WindowsError: raise IterationError for i in itertools.count(): try: val = winreg.EnumValue(key, i) yield (str(val[1]), str(val[0])) except EnvironmentError: break

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  • I find a problem with sending receiving parameter

    - by kawtousse
    how to get the xml translation to html dropdownlist with ajax. I send the parameter with GET method but the JSP FILE THAT GENERATES THE XML DONT RECEIVE IT. var url="responsexml.jsp"; url=url+"?projectCode="+prj.options[prj.selectedIndex].value; xmlhttp.onreadystatechange=stateChanged; xmlhttp.open("GET",url,true); xmlhttp.send(null); and then in responsexml.jsp I do like that: <% String projectcode= (String)request.getParameter("projectCode"); System.out.println("++++projectCode:=" +projectcode); Session s = null; Transaction tx; try { s = HibernateUtil.currentSession(); tx = s.beginTransaction(); Query query = s.createQuery("SELECT from Wa wa where wa.ProjectCode='"+projectcode+"'"); response.setContentType("text/xml"); PrintWriter output = response.getWriter(); output.write( "<?xml version=\"1.0\" encoding=\"utf-8\"?>"); //response.setHeader("Cache-Control", "no-cache"); //constriure le xml if(projectcode!=null) { for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()) { Wa object=(Wa)it.next(); //out.print( "<item id=\"" +object.getIdWA() + "\" name=\"" + object.getWAName() + "\" />"); output.write("<wa>"); output.write( "<item id=\"" + object.getIdWA() + "\" name=\"" + object.getWAName() + "\" />"); output.write("</wa>"); } } } } catch (HibernateException e) { e.printStackTrace(); } %> </body> </html> With this code I dont have my xml file. I got this error: The server did not understand the request, or the request was invalid. Erreur de traitement de la ressource http://www.w3.o... PLEASE HELP.

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  • ajax to populate an input type text

    - by kawtousse
    hi, I have an input type text that i want to populate it with a value from data base using the ajax technique. first i define my text zone like the following: <td><input type=text id='st' value=" " name='stname' onclick="donnom();" /></td> in javascript i do the following: xhr5.onreadystatechange = function(){ if(xhr5.readyState == 4 && xhr5.status == 200) { selects5 = xhr5.responseText; // On se sert de innerHTML pour rajouter les options a la liste document.getElementById('st').innerHTML = selects5; } }; xhr5.open("POST","ajaxIDentifier5.jsp",true); xhr5.setRequestHeader('Content-Type','application/x-www-form-urlencoded'); id=document.getElementById(idIdden).value; xhr5.send("id="+id); in IDentifier5.jsp i put the next code: '<%String id=request.getParameter("id"); System.out.println("idDailyTimeSheet ajaxIDentifier5 as is:"+id); Session s = null; Transaction tx; try { s= HibernateUtil.currentSession(); tx=s.beginTransaction(); Query query = s.createQuery("select from Dailytimesheet dailytimesheet where dailytimesheet.IdDailyTimeSheet="+id+" " ); for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()) { Dailytimesheet object=(Dailytimesheet)it.next(); out.print( "<input type=\"text\" id=\"st1\" value=\""+object.getTimeFrom()+"\" name=\"starting\" onclick=\"donnom()\" ></input>"); } } }catch (HibernateException e) { e.printStackTrace();} %> i want to get only the value in the input type text populated from database because after that i will be able to change it . thanks for help.

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  • How to get at contents of placeholder::_1

    - by sheepsimulator
    I currently have the following code: using boost::bind; typedef boost::signal<void(EventDataItem&)> EventDataItemSignal; class EventDataItem { ... EventDataItemSignal OnTrigger; ... } typedef std::list< shared_ptr<EventDataItem> > DataItemList; typedef std::list<boost::signals::connection> ConnectionList; class MyClass { void OnStart() { DataItemList dilItems; ConnectionList clConns; DataItemList::iterator iterDataItems; for(iterDataItems = dilItems.begin(); iterDataItems != dilItems.end(); iterDataItems++) { // Create Connections from Triggers clConns.push_back((*iterDataItems)->OnTrigger.connect( bind(&MyClass::OnEventTrigger, this))); } } void OnEventTrigger() { // ... Do stuff on Trigger... } } I'd like to change MyClass::OnStart to use std::transform to achieve the same thing: void MyClass::OnStart() { DataItemList dilItems; ConnectionList clConns; // Resize connection list to match number of data items clConns.resize(dilItems.size()); // Build connection list from Items // note: errors on the placeholder _1->OnTrigger std::transform(dilItems.begin(), dilItems.end(), clConns.begin(), bind(&EventDataItemSignal::connect, _1->OnTrigger, bind(&MyClass::Stuff, this))); } However, my hiccup is _1-OnTrigger. How can I reference OnTrigger from placeholder _1?

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  • How to set up single array or dictionary for use in multiple datasources?

    - by Roman
    I have multiple TableViewDatasources that need to display list of objects form same pool depending of certain property. E.g. object.flag1 is set- it will show up in TableView1 object.flag2 is set- it will show up in TableView2 The obvious way would be to have separate arrays for each TableView, But same object may appear in different arrays. Also I need to update objects very often or access all objects through same array. How do I setup a single dictionary or array to have all objects in one structure? To put it in another way: When table view or selection changes, application need to redraw TableViews with the new data. Application have to access the pool of objects and search through them using iterator and accessing each object and its properties. I think that this is an expensive operation and want to avoid that. Perhaps maybe by making a global pool of objects a dictionary and exposing objects properties as dictionary fields. So instead of iterating global pool of objects I could access global pool Dicitonary in a manner of database by selecting objects that has fields that match particular criteria. Anyone know any example of doing that?

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  • Why does one of these statements compile in Scala but not the other?

    - by Jeff
    (Note: I'm using Scala 2.7.7 here, not 2.8). I'm doing something pretty simple -- creating a map based on the values in a simple, 2-column CSV file -- and I've completed it easily enough, but I'm perplexed at why my first attempt didn't compile. Here's the code: // Returns Iterator[String] private def getLines = Source.fromFile(csvFilePath).getLines // This doesn't compile: def mapping: Map[String,String] = { Map(getLines map { line: String => val pairArr = line.split(",") pairArr(0) -> pairArr(1).trim() }.toList:_*) } // This DOES compile def mapping: Map[String,String] = { def strPair(line: String): (String,String) = { val pairArr = line.split(",") pairArr(0) -> pairArr(1).trim() } Map(getLines.map( strPair(_) ).toList:_*) } The compiler error is CsvReader.scala:16: error: value toList is not a member of (St ring) = (java.lang.String, java.lang.String) [scalac] possible cause: maybe a semicolon is missing before `value toList'? [scalac] }.toList:_*) [scalac] ^ [scalac] one error found So what gives? They seem like they should be equivalent to me, apart from the explicit function definition (vs. anonymous in the nonworking example) and () vs. {}. If I replace the curly braces with parentheses in the nonworking example, the error is "';' expected, but 'val' found." But if I remove the local variable definition and split the string twice AND use parens instead of curly braces, it compiles. Can someone explain this difference to me, preferably with a link to Scala docs explaining the difference between parens and curly braces when used to surround method arguments?

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  • Java/XML: Good "Stream-based" Alternative to JAXB?

    - by Jan
    Hello Experts, JAXB makes working with XML so much easier, but I have currently a big problem, that the documents I have to process are too large for an in memory unmarshalling that JAXB does. The data can be up to 4GB per document. The datastructure I will have to process is very simple and flat: With a root element and millions of “elements”… <root> <element> <sub>foo</sub> </element> <element> <sub>foo</sub> </element> </root> May questions are: Does JAXB maybe somehow support unmarshalling in a “streambased” way, that does not require to build the whole objecttree in memory but rather gives me some kind of “Iterator” to the elements, element by element? (Maybe I just missed that somehow…) If not what are your proposals for an good alternative with a a. “flat learningcurve, ideally very similar to JAXB b. AND VERY IMPORTANT: Ideally with the possibility / tool for the generation of the unarshaller code from an XSD file OR annotated Java Class 3.(I have searched SO and those to library that ended up on my “watchlist” (without comparing them closer) were Apache XML Beans and Xstream… What other libraries are maybe even better for the purpose and what are the disadvantages, adavangaes… Thank you very much!!! Jan

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  • GAE datastore querying integer fields

    - by ParanoidAndroid
    I notice strange behavior when querying the GAE datastore. Under certain circumstances Filter does not work for integer fields. The following java code reproduces the problem: log.info("start experiment"); DatastoreService datastore = DatastoreServiceFactory.getDatastoreService(); int val = 777; // create and store the first entity. Entity testEntity1 = new Entity(KeyFactory.createKey("Test", "entity1")); Object value = new Integer(val); testEntity1.setProperty("field", value); datastore.put(testEntity1); // create the second entity by using BeanUtils. Test test2 = new Test(); // just a regular bean with an int field test2.setField(val); Entity testEntity2 = new Entity(KeyFactory.createKey("Test", "entity2")); Map<String, Object> description = BeanUtilsBean.getInstance().describe(test2); for(Entry<String,Object> entry:description.entrySet()){ testEntity2.setProperty(entry.getKey(), entry.getValue()); } datastore.put(testEntity2); // now try to retrieve the entities from the database... Filter equalFilter = new FilterPredicate("field", FilterOperator.EQUAL, val); Query q = new Query("Test").setFilter(equalFilter); Iterator<Entity> iter = datastore.prepare(q).asIterator(); while (iter.hasNext()) { log.info("found entity: " + iter.next().getKey()); } log.info("experiment finished"); the log looks like this: INFO: start experiment INFO: found entity: Test("entity1") INFO: experiment finished For some reason it only finds the first entity even though both entities are actually stored in the datastore and both 'field' values are 777 (I see it in the Datastore Viewer)! Why does it matter how the entity is created? I would like to use BeanUtils, because it is convenient. The same problem occurs on the local devserver and when deployed to GAE.

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  • general learning methodology

    - by momo
    just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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  • how to implement a sparse_vector class

    - by Neil G
    I am implementing a templated sparse_vector class. It's like a vector, but it only stores elements that are different from their default constructed value. So, sparse_vector would store the index-value pairs for all indices whose value is not T(). I am basing my implementation on existing sparse vectors in numeric libraries-- though mine will handle non-numeric types T as well. I looked at boost::numeric::ublas::coordinate_vector and eigen::SparseVector. Both store: size_t* indices_; // a dynamic array T* values_; // a dynamic array int size_; int capacity_; Why don't they simply use vector<pair<size_t, T>> data_; My main question is what are the pros and cons of both systems, and which is ultimately better? The vector of pairs manages size_ and capacity_ for you, and simplifies the accompanying iterator classes; it also has one memory block instead of two, so it incurs half the reallocations, and might have better locality of reference. The other solution might search more quickly since the cache lines fill up with only index data during a search. There might also be some alignment advantages if T is an 8-byte type? It seems to me that vector of pairs is the better solution, yet both containers chose the other solution. Why?

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  • No output got after execution.

    - by wilson88
    I am still stuck with getting output for a copied vector. Probably something am not doing right. I get no output. void Auctioneer::accept_bids(const BidList& bid){ BidList list; BidList list2; BidList::const_iterator iter; copy (list.begin(),list.end(), back_inserter(list2)); for(iter=list2.begin(); iter != list2.end(); iter++) { const Bid& bid = *iter; // Get a reference to the Bid object that the iterator points to cout << "Bid id : " << bid.bidId << endl; cout << "Trd id : " << bid.trdId << endl; cout << "Quantity: " << bid.qty << endl; cout << "Price : " << bid.price << endl; cout << "Type : " << bid.type << endl; } }

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  • How can I overlay images over one another in Java?

    - by Sam
    So I have been posting all over and have yet to get a solid answer: I have created an image resizing class, with a crop method. The cropping works great. The issue that I am having is the background color that I specify in the drawImage function of Graphics is not working correctly. It defaults to black as the background regardless of what I supply (in this case Color.WHITE). Also, the overlaying image or top most image (comes from a file) is being inverted (I think it is) or otherwise discolored. Just so you can conceptualize this a little bit better, I am taking a jpeg and overlaying it on top of a new BufferedImage, the new buffered image's background is not being set. Here is the code below that I am working with: public void Crop(int Height, int Width, int SourceX, int SourceY) throws Exception { //output height and width int OutputWidth = this.OutputImage.getWidth(); int OutputHeight = this.OutputImage.getHeight(); //create output streams ByteArrayOutputStream MyByteArrayOutputStream = new ByteArrayOutputStream(); MemoryCacheImageOutputStream MyMemoryCacheImageOutputStream = new MemoryCacheImageOutputStream(MyByteArrayOutputStream); //Create a new BufferedImage BufferedImage NewImage = new BufferedImage(Width, Height, BufferedImage.TYPE_INT_RGB); Graphics MyGraphics = NewImage.createGraphics(); MyGraphics.drawImage(this.OutputImage, -SourceX, -SourceY, OutputWidth, OutputHeight, Color.WHITE, null); // Get Writer and set compression Iterator MyIterator = ImageIO.getImageWritersByFormatName("png"); if (MyIterator.hasNext()) { //get image writer ImageWriter MyImageWriter = (ImageWriter)MyIterator.next(); //get params ImageWriteParam MyImageWriteParam = MyImageWriter.getDefaultWriteParam(); //set outputstream MyImageWriter.setOutput(MyMemoryCacheImageOutputStream); //create new ioimage IIOImage MyIIOImage = new IIOImage(NewImage, null, null); //write new image MyImageWriter.write(null, MyIIOImage, MyImageWriteParam); } //convert output stream back to inputstream ByteArrayInputStream MyByteArrayInputStream = new ByteArrayInputStream(MyByteArrayOutputStream.toByteArray()); MemoryCacheImageInputStream MyMemoryCacheImageInputStream = new MemoryCacheImageInputStream(MyByteArrayInputStream); //resassign as a buffered image this.OutputImage = ImageIO.read(MyMemoryCacheImageInputStream); }

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  • Persistant Http client connections in java

    - by Akusete
    I am trying to write a simple Http client application in Java and am a bit confused by the seemingly different ways to establish Http client connections, and efficiently re-use the objects. Current I am using the following steps (I have left out exception handling for simplicity) Iterator<URI> uriIterator = someURIs(); HttpClient client = new DefaultHttpClient(); while (uriIterator.hasNext()) { URI uri = uriIterator.next(); HttpGet request = new HttpGet(uri); HttpResponse response = client.execute(request); HttpEntity entity = response.getEntity(); InputStream s = entity.getContent(); processStream (); s.close(); } In regard to the code above, my questions is: Assuming all URI's are pointing to the same host (but different resources on that host). What is the recommended way to use a single http connection for all requests? And how do you close the connection after the last request? --edit: Also what is the difference between using uri.openConnection(), versus HttpClient? Which is preferable, and what other methods exist?

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  • Remove pointer object whose reference is mantained in three different lists

    - by brainydexter
    I am not sure how to approach this problem: 'Player' class mantains a list of Bullet* objects: class Player { protected: std::list< Bullet* > m_pBullet_list; } When the player fires a Bullet, it is added to this list. Also, inside the constructor of bullet, a reference of the same object is updated in CollisionMgr, where CollisionMgr also mantains a list of Bullet*. Bullet::Bullet(GameGL*a_pGameGL, Player*a_pPlayer) : GameObject( a_pGameGL ) { m_pPlayer = a_pPlayer; m_pGameGL->GetCollisionMgr()->AddBullet(this); } class CollisionMgr { void AddBullet(Bullet* a_pBullet); protected: std::list< Bullet*> m_BulletPList; } In CollisionMgr.Update(); based on some conditions, I populate class Cell which again contain a list of Bullet*. Finally, certain conditions qualify a Bullet to be deleted. Now, these conditions are tested upon while iterating through a Cell's list. So, if I have to delete the Bullet object, from all these places, how should I do it so that there are no more dangling references to it? std::list< Bullet*>::iterator bullet_it; for( bullet_it = (a_pCell->m_BulletPList).begin(); bullet_it != (a_pCell->m_BulletPList).end(); bullet_it++) { bool l_Bullet_trash = false; Bullet* bullet1 = *bullet_it; // conditions would set this to true if ( l_Bullet_Trash ) // TrashBullet( bullet1 ); continue; } Also, I was reading about list::remove, and it mentions that it calls the destructor of the object we are trying to delete. Given this info, if I delete from one list, the object does not exist, but the list would still contain a reference to it..How do I handle all these problems ? Can someone please help me here ? Thanks PS: If you want me to post more code or provide explanation, please do let me know.

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  • C++ destructos causing crash's

    - by larsonator
    ok, so i got a some what intricate program that simulates the uni systems of students, units, and students enrolling in units. Students are stored in a binary search tree, Units are stored in a standard list. Student has a list of Unit Pointers, to store which units he/she is enrolled in Unit has a list of Student pointers, to store students which are enrolled in that unit. The unit collections (storing units in a list) as made as a static variable where the main function is, as is the Binary search tree of students. when its finaly time to close the program, i call the destructors of each. but at some stage, during the destructors on the unit side, Unhandled exception at 0x002e4200 in ClassAllocation.exe: 0xC0000005: Access violation reading location 0x00000000. UnitCollection destructor: UnitCol::~UnitCol() { list<Unit>::iterator itr; for(itr = UnitCollection.begin(); itr != UnitCollection.end();) { UnitCollection.pop_front(); itr = UnitCollection.begin(); } } Unit Destructor Unit::~Unit() { } now i got the same sorta problem on the student side of things BST destructors void StudentCol::Destructor(const BTreeNode * r) { if(r!= 0) { Destructor(r->getLChild()); Destructor(r->getRChild()); delete r; } } StudentCol::~StudentCol() { Destructor(root); } Student Destructor Student::~Student() { } so yeah any help would be greatly appreciated

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  • std::list : get next element

    - by sheepsimulator
    I'm trying to build a string using data elements stored in a std::list, where I want commas placed only between the elements (ie, if elements are {A,B,C,D} in list, result string should be "A,B,C,D". This code does not work: typedef std::list< shared_ptr<EventDataItem> > DataItemList; // ... std::string Compose(DataItemList& dilList) { std::stringstream ssDataSegment; for(iterItems = dilList.begin(); iterItems = dilList.end(); iterItems++) { // Lookahead in list to see if next element is end if((iterItems + 1) == dilList.end()) { ssDataSegment << (*iterItems)->ToString(); } else { ssDataSegment << (*iterItems)->ToString() << ","; } } return ssDataSegment.str(); } How do I get at "the-next-item" in a std::list using an iterator? I would expect that it's a linked-list, why can't I get at the next item?

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  • Vector insert() causes program to crash

    - by wrongusername
    This is the first part of a function I have that's causing my program to crash: vector<Student> sortGPA(vector<Student> student) { vector<Student> sorted; Student test = student[0]; cout << "here\n"; sorted.insert(student.begin(), student[0]); cout << "it failed.\n"; ... It crashes right at the sorted part because I can see "here" on the screen but not "it failed." The following error message comes up: Debug Assertion Failed! (a long path here...) Expression: vector emplace iterator outside range For more information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts. I'm not sure what's causing the problem now, since I have a similar line of code elsewhere student.insert(student.begin() + position(temp, student), temp); that does not crash (where position returns an int and temp is another declaration of a struct Student). What can I do to resolve the problem, and how is the first insert different from the second one?

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  • __toString magic and type coercion

    - by TomcatExodus
    I've created a Template class for managing views and their associated data. It implements Iterator and ArrayAccess, and permits "sub-templates" for easy usage like so: <p><?php echo $template['foo']; ?></p> <?php foreach($template->post as $post): ?> <p><?php echo $post['bar']; ?></p> <?php endforeach; ?> Anyways, rather than using inline core functions, such as hash() or date(), I figured it would be useful to create a class called TemplateData, which would act as a wrapper for any data stored in the templates. This way, I can add a list of common methods for formatting, for example: echo $template['foo']->asCase('upper'); echo $template['bar']->asDate('H:i:s'); //etc.. When a value is set via $template['foo'] = 'bar'; in the controllers, the value of 'bar' is stored in it's own TemplateData object. I've used the magic __toString() so when you echo a TemplateData object, it casts to (string) and dumps it's value. However, despite the mantra controllers and views should not modify data, whenever I do something like this: $template['foo'] = 1; echo $template['foo'] + 1; //exception It dies on a Object of class TemplateData could not be converted to int; Unless I recast $template['foo'] to a string: echo ((string) $template['foo']) + 1; //outputs 2 Sort of defeats the purpose having to jump through that hoop. Are there any workarounds for this sort of behavior that exist, or should I just take this as it is, an incidental prevention of data modification in views?

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