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  • Can't build full html table in QTextEdit with std::for_each...

    - by mosg
    Hi. Here is my code function: void ReportHistory::update(void) { ui.output->clear(); ui.output->setCurrentFont(QFont("Arial", 8, QFont::Normal)); QString title = "My Title"; QStringList headers = QString("Header1,Header2,Header3,Header4,Header5,Header6").split(","); QString html = QString( "<html>" \ "<head>" \ "<meta Content=\"Text/html; charset=Windows-1251\">" \ "<title>%1</title>" \ "</head>" \ "<body bgcolor=#ffffff link=#5000A0>" \ "<p>%1</p>" \ "<table border=1 cellspacing=0 cellpadding=2>" \ "<tr bgcolor=#f0f0f0>" ).arg(title); foreach (QString header, headers) { html.append(QString("<th>%1</th>").arg(header)); } html.append("</tr>"); struct Fill { QString html_; Analytics::NavHistory::History::value_type prev_; Fill(QString html) : html_(html) {} void operator ()(const Analytics::NavHistory::History::value_type& entry) { QStringList line = (QString( "%1|%2|%3|%4|%5|%6" ).arg(value1, 15) .arg(value2 ? ' ' : 'C', 8) .arg(value3, 15) .arg(value4, 15, 'f', 4) .arg(value5, 15) .arg(value6, 15, 'f', 4)).split("|"); html_.append("<tr>"); foreach (QString item, line) { html_.append("<td bkcolor=0>%1</td>").arg(item); } html_.append("</tr>"); prev_ = entry; } }; std::for_each(history_->data().begin(), history_->data().end(), Fill(html)); html.append( "</table>" \ "</body>" \ "</html>"); ui.output->setHtml(html); } Where: ui.output is a pointer to QTextEdit. Question: the ui.output just show me the headers, and not the full table, what is wrong? Thanks.

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  • Segmentation fault when creating a Phonon MediaObject

    - by Luke Hansford
    I have music playing program made using PySide which uses Phonon to playback audio. I updated to MacOS X Mavericks a few days ago, which meant I needed to reinstall PySide. I'm not sure which of these actions has caused this, but now whenever I try to create a Phonon MediaObject I get a Segmentation Fault: 11 from Python. It's not just in my program, it happens when trying to create a MediaObject in Python without any other actions. I'm getting the following error message from my Mac whenever it crashes: Process: Python [13711] Path: /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python Identifier: org.python.python Version: 2.7.5 (2.7.5) Code Type: X86-64 (Native) Parent Process: bash [13707] Responsible: Terminal [13704] User ID: 501 Date/Time: 2013-11-01 19:47:53.164 +1000 OS Version: Mac OS X 10.9 (13A603) Report Version: 11 Anonymous UUID: C2686854-18CA-9D37-26E9-60050E3C4DA6 Sleep/Wake UUID: BB983BF6-CCE2-44D1-82A0-1C73382DFFE4 Crashed Thread: 0 Dispatch queue: com.apple.main-thread Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000008 VM Regions Near 0x8: --> __TEXT 00000001082e8000-00000001082e9000 [ 4K] r-x/rwx SM=COW /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 QtCore 0x000000010a1b34cb QObject::moveToThread(QThread*) + 17 1 QtDBus 0x000000010d55f98b QDBusDefaultConnection::QDBusDefaultConnection(QDBusConnection::BusType, char const*) + 171 2 QtDBus 0x000000010d55ebdf QDBusConnection::sessionBus() + 71 3 phonon 0x000000010d50228d Phonon::FactoryPrivate::FactoryPrivate() + 189 4 phonon 0x000000010d5024d5 Phonon::$_249::operator->() + 99 5 phonon 0x000000010d502991 Phonon::Factory::registerFrontendObject(Phonon::MediaNodePrivate*) + 17 6 phonon 0x000000010d50b27e Phonon::MediaNodePrivate::MediaNodePrivate(Phonon::MediaNodePrivate::CastId) + 80 7 phonon 0x000000010d50f570 Phonon::MediaObjectPrivate::MediaObjectPrivate() + 24 8 phonon 0x000000010d50be9d Phonon::MediaObject::MediaObject(QObject*) + 45 9 phonon.so 0x000000010d42f24a Sbk_Phonon_MediaObject_Init + 458 10 org.python.python 0x0000000108338707 type_call + 189 11 org.python.python 0x00000001082f74fd PyObject_Call + 101 12 org.python.python 0x00000001083714f0 PyEval_EvalFrameEx + 15525 13 org.python.python 0x0000000108373aaf fast_function + 182 14 org.python.python 0x0000000108370919 PyEval_EvalFrameEx + 12494 15 org.python.python 0x000000010836d721 PyEval_EvalCodeEx + 1638 16 org.python.python 0x000000010836d0b5 PyEval_EvalCode + 54 17 org.python.python 0x000000010838beb8 run_mod + 53 18 org.python.python 0x000000010838bf5f PyRun_FileExFlags + 137 19 org.python.python 0x000000010838baad PyRun_SimpleFileExFlags + 718 20 org.python.python 0x000000010839c58b Py_Main + 3039 21 libdyld.dylib 0x00007fff8e4fb5fd start + 1 Thread 1:: Dispatch queue: com.apple.libdispatch-manager 0 libsystem_kernel.dylib 0x00007fff8c938662 kevent64 + 10 1 libdispatch.dylib 0x00007fff923e743d _dispatch_mgr_invoke + 239 2 libdispatch.dylib 0x00007fff923e7152 _dispatch_mgr_thread + 52 Thread 2: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 3: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 4: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 0 crashed with X86 Thread State (64-bit): rax: 0x00007feba0d19700 rbx: 0x000000010d5b7098 rcx: 0x00000000002f4180 rdx: 0x000000000012c040 rdi: 0x0000000000000000 rsi: 0x00007feba0d19700 rbp: 0x00007fff57917210 rsp: 0x00007fff579171d0 r8: 0x00007feba0fd5d10 r9: 0x00007feba0ff5310 r10: 0x0000000019c04cbe r11: 0x0000000070769b38 r12: 0x00007fff57917220 r13: 0x00007feba0c07190 r14: 0x0000000000000000 r15: 0x00007feba0fe1430 rip: 0x000000010a1b34cb rfl: 0x0000000000010202 cr2: 0x0000000000000008 Logical CPU: 0 Error Code: 0x00000004 Trap Number: 14 Anyone have any ideas about what is happening?

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  • Efficiency of Java "Double Brace Initialization"?

    - by Jim Ferrans
    In Hidden Features of Java the top answer mentions Double Brace Initialization, with a very enticing syntax: Set<String> flavors = new HashSet<String>() {{ add("vanilla"); add("strawberry"); add("chocolate"); add("butter pecan"); }}; This idiom creates an anonymous inner class with just an instance initializer in it, which "can use any [...] methods in the containing scope". Main question: Is this as inefficient as it sounds? Should its use be limited to one-off initializations? (And of course showing off!) Second question: The new HashSet must be the "this" used in the instance initializer ... can anyone shed light on the mechanism? Third question: Is this idiom too obscure to use in production code? Summary: Very, very nice answers, thanks everyone. On question (3), people felt the syntax should be clear (though I'd recommend an occasional comment, especially if your code will pass on to developers who may not be familiar with it). On question (1), The generated code should run quickly. The extra .class files do cause jar file clutter, and slow program startup slightly (thanks to coobird for measuring that). Thilo pointed out that garbage collection can be affected, and the memory cost for the extra loaded classes may be a factor in some cases. Question (2) turned out to be most interesting to me. If I understand the answers, what's happening in DBI is that the anonymous inner class extends the class of the object being constructed by the new operator, and hence has a "this" value referencing the instance being constructed. Very neat. Overall, DBI strikes me as something of an intellectual curiousity. Coobird and others point out you can achieve the same effect with Arrays.asList, varargs methods, Google Collections, and the proposed Java 7 Collection literals. Newer JVM languages like Scala, JRuby, and Groovy also offer concise notations for list construction, and interoperate well with Java. Given that DBI clutters up the classpath, slows down class loading a bit, and makes the code a tad more obscure, I'd probably shy away from it. However, I plan to spring this on a friend who's just gotten his SCJP and loves good natured jousts about Java semantics! ;-) Thanks everyone!

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  • Singleton: How should it be used

    - by Loki Astari
    Edit: From another question I provided an answer that has links to a lot of questions/answers about singeltons: More info about singletons here: So I have read the thread Singletons: good design or a crutch? And the argument still rages. I see Singletons as a Design Pattern (good and bad). The problem with Singleton is not the Pattern but rather the users (sorry everybody). Everybody and their father thinks they can implement one correctly (and from the many interviews I have done, most people can't). Also because everybody thinks they can implement a correct Singleton they abuse the Pattern and use it in situations that are not appropriate (replacing global variables with Singletons!). So the main questions that need to be answered are: When should you use a Singleton How do you implement a Singleton correctly My hope for this article is that we can collect together in a single place (rather than having to google and search multiple sites) an authoritative source of when (and then how) to use a Singleton correctly. Also appropriate would be a list of Anti-Usages and common bad implementations explaining why they fail to work and for good implementations their weaknesses. So get the ball rolling: I will hold my hand up and say this is what I use but probably has problems. I like "Scott Myers" handling of the subject in his books "Effective C++" Good Situations to use Singletons (not many): Logging frameworks Thread recycling pools /* * C++ Singleton * Limitation: Single Threaded Design * See: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf * For problems associated with locking in multi threaded applications * * Limitation: * If you use this Singleton (A) within a destructor of another Singleton (B) * This Singleton (A) must be fully constructed before the constructor of (B) * is called. */ class MySingleton { private: // Private Constructor MySingleton(); // Stop the compiler generating methods of copy the object MySingleton(MySingleton const& copy); // Not Implemented MySingleton& operator=(MySingleton const& copy); // Not Implemented public: static MySingleton& getInstance() { // The only instance // Guaranteed to be lazy initialized // Guaranteed that it will be destroyed correctly static MySingleton instance; return instance; } }; OK. Lets get some criticism and other implementations together. :-)

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  • Lucene.NET search index approach

    - by Tim Peel
    Hi, I am trying to put together a test case for using Lucene.NET on one of our websites. I'd like to do the following: Index in a single unique id. Index across a comma delimitered string of terms or tags. For example. Item 1: Id = 1 Tags = Something,Separated-Term I will then be structuring the search so I can look for documents against tag i.e. tags:something OR tags:separate-term I need to maintain the exact term value in order to search against it. I have something running, and the search query is being parsed as expected, but I am not seeing any results. Here's some code. My parser (_luceneAnalyzer is passed into my indexing service): var parser = new QueryParser(Lucene.Net.Util.Version.LUCENE_CURRENT, "Tags", _luceneAnalyzer); parser.SetDefaultOperator(QueryParser.Operator.AND); return parser; My Lucene.NET document creation: var doc = new Document(); var id = new Field( "Id", NumericUtils.IntToPrefixCoded(indexObject.id), Field.Store.YES, Field.Index.NOT_ANALYZED, Field.TermVector.NO); var tags = new Field( "Tags", string.Join(",", indexObject.Tags.ToArray()), Field.Store.NO, Field.Index.ANALYZED, Field.TermVector.YES); doc.Add(id); doc.Add(tags); return doc; My search: var parser = BuildQueryParser(); var query = parser.Parse(searchQuery); var searcher = Searcher; TopDocs hits = searcher.Search(query, null, max); IList<SearchResult> result = new List<SearchResult>(); float scoreNorm = 1.0f / hits.GetMaxScore(); for (int i = 0; i < hits.scoreDocs.Length; i++) { float score = hits.scoreDocs[i].score * scoreNorm; result.Add(CreateSearchResult(searcher.Doc(hits.scoreDocs[i].doc), score)); } return result; I have two documents in my index, one with the tag "Something" and one with the tags "Something" and "Separated-Term". It's important for the - to remain in the terms as I want an exact match on the full value. When I search with "tags:Something" I do not get any results. Question What Analyzer should I be using to achieve the search index I am after? Are there any pointers for putting together a search such as this? Why is my current search not returning any results? Many thanks

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  • How can arguments to variadic functions be passed by reference in PHP?

    - by outis
    Assuming it's possible, how would one pass arguments by reference to a variadic function without generating a warning in PHP? We can no longer use the '&' operator in a function call, otherwise I'd accept that (even though it would be error prone, should a coder forget it). What inspired this is are old MySQLi wrapper classes that I unearthed (these days, I'd just use PDO). The only difference between the wrappers and the MySQLi classes is the wrappers throw exceptions rather than returning FALSE. class DBException extends RuntimeException {} ... class MySQLi_throwing extends mysqli { ... function prepare($query) { $stmt = parent::prepare($query); if (!$stmt) { throw new DBException($this->error, $this->errno); } return new MySQLi_stmt_throwing($this, $query, $stmt); } } // I don't remember why I switched from extension to composition, but // it shouldn't matter for this question. class MySQLi_stmt_throwing /* extends MySQLi_stmt */ { protected $_link, $_query, $_delegate; public function __construct($link, $query, $prepared) { //parent::__construct($link, $query); $this->_link = $link; $this->_query = $query; $this->_delegate = $prepared; } function bind_param($name, &$var) { return $this->_delegate->bind_param($name, $var); } function __call($name, $args) { //$rslt = call_user_func_array(array($this, 'parent::' . $name), $args); $rslt = call_user_func_array(array($this->_delegate, $name), $args); if (False === $rslt) { throw new DBException($this->_link->error, $this->errno); } return $rslt; } } The difficulty lies in calling methods such as bind_result on the wrapper. Constant-arity functions (e.g. bind_param) can be explicitly defined, allowing for pass-by-reference. bind_result, however, needs all arguments to be pass-by-reference. If you call bind_result on an instance of MySQLi_stmt_throwing as-is, the arguments are passed by value and the binding won't take. try { $id = Null; $stmt = $db->prepare('SELECT id FROM tbl WHERE ...'); $stmt->execute() $stmt->bind_result($id); // $id is still null at this point ... } catch (DBException $exc) { ... } Since the above classes are no longer in use, this question is merely a matter of curiosity. Alternate approaches to the wrapper classes are not relevant. Defining a method with a bunch of arguments taking Null default values is not correct (what if you define 20 arguments, but the function is called with 21?). Answers don't even need to be written in terms of MySQL_stmt_throwing; it exists simply to provide a concrete example.

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  • Scipy Negative Distance? What?

    - by disappearedng
    I have a input file which are all floating point numbers to 4 decimal place. i.e. 13359 0.0000 0.0000 0.0001 0.0001 0.0002` 0.0003 0.0007 ... (the first is the id). My class uses the loadVectorsFromFile method which multiplies it by 10000 and then int() these numbers. On top of that, I also loop through each vector to ensure that there are no negative values inside. However, when I perform _hclustering, I am continually seeing the error, "Linkage Z contains negative values". I seriously think this is a bug because: I checked my values, the values are no where small enough or big enough to approach the limits of the floating point numbers and the formula that I used to derive the values in the file uses absolute value (my input is DEFINITELY right). Can someone enligten me as to why I am seeing this weird error? What is going on that is causing this negative distance error? ===== def loadVectorsFromFile(self, limit, loc, assertAllPositive=True, inflate=True): """Inflate to prevent "negative" distance, we use 4 decimal points, so *10000 """ vectors = {} self.winfo("Each vector is set to have %d limit in length" % limit) with open( loc ) as inf: for line in filter(None, inf.read().split('\n')): l = line.split('\t') if limit: scores = map(float, l[1:limit+1]) else: scores = map(float, l[1:]) if inflate: vectors[ l[0]] = map( lambda x: int(x*10000), scores) #int might save space else: vectors[ l[0]] = scores if assertAllPositive: #Assert that it has no negative value for dirID, l in vectors.iteritems(): if reduce(operator.or_, map( lambda x: x < 0, l)): self.werror( "Vector %s has negative values!" % dirID) return vectors def main( self, inputDir, outputDir, limit=0, inFname="data.vectors.all", mappingFname='all.id.features.group.intermediate'): """ Loads vector from a file and start clustering INPUT vectors is { featureID: tfidfVector (list), } """ IDFeatureDic = loadIdFeatureGroupDicFromIntermediate( pjoin(self.configDir, mappingFname)) if not os.path.exists(outputDir): os.makedirs(outputDir) vectors = self.loadVectorsFromFile( limit, pjoin( inputDir, inFname)) for threshold in map( lambda x:float(x)/30, range(20,30)): clusters = self._hclustering(threshold, vectors) if clusters: outputLoc = pjoin(outputDir, "threshold.%s.result" % str(threshold)) with open(outputLoc, 'w') as outf: for clusterNo, cluster in clusters.iteritems(): outf.write('%s\n' % str(clusterNo)) for featureID in cluster: feature, group = IDFeatureDic[featureID] outline = "%s\t%s\n" % (feature, group) outf.write(outline.encode('utf-8')) outf.write("\n") else: continue def _hclustering(self, threshold, vectors): """function which you should call to vary the threshold vectors: { featureID: [ tfidf scores, tfidf score, .. ] """ clusters = defaultdict(list) if len(vectors) > 1: try: results = hierarchy.fclusterdata( vectors.values(), threshold, metric='cosine') except ValueError, e: self.werror("_hclustering: %s" % str(e)) return False for i, featureID in enumerate( vectors.keys()):

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  • setting ruby hash .default to a list

    - by matpalm
    i thought i understood what the default method does to a hash... give a default value for a key if it doesn't exist irb(main):001:0> a = {} => {} irb(main):002:0> a.default = 4 => 4 irb(main):003:0> a[8] => 4 irb(main):004:0> a[9] += 1 => 5 irb(main):005:0> a => {9=>5} all good. but if i set the default to be a empty list, or empty hash, i dont understand it's behaviour at all.... irb(main):001:0> a = {} => {} irb(main):002:0> a.default = [] => [] irb(main):003:0> a[8] << 9 => [9] # great! irb(main):004:0> a => {} # ?! would have expected {8=>[9]} irb(main):005:0> a[8] => [8] # awesome! irb(main):006:0> a[9] => [9] # unawesome! shouldn't this be [] ?? i was hoping / expecting the same behaviour as if i had used the ||= operator... irb(main):001:0> a = {} => {} irb(main):002:0> a[8] ||= [] => [] irb(main):003:0> a[8] << 9 => [9] irb(main):004:0> a => {8=>[9]} irb(main):005:0> a[9] => nil can anyone explain what is going on ???

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  • How to make Flash 'play well with others'?

    - by Sensei James
    What up fam. So this isn't a question asking about memory management schemes; for those of you who may not know, the Flash Virtual Machine relies on garbage collection by using reference counting and mark and sweep (for good coverage of these topics, check out Grant Skinner's article and presentation). And yes, Flash also provides the "delete" operator, which can (unfortunately only) be used to remove the properties of dynamic objects. What I want to know is how to make it so that Flash programs don't continue to consume CPU and memory while running in the background (save loading content or communicating remotely, for example). The motivation for this question comes in part from Apple's ban on cross compiled applications (in its SDK 4) on the grounds that they do not behave as predicted with the multitasking feature central to iPhone OS 4. My intention is not only to make Flash programs that will 'pass muster' as far as multitasking in iPhone OS 4, but also to simply make better (behaving) Flash programs. Put another way, how might a Flash application mimic the multitasking feature of iPhone OS 4? Does the Flash API provide the means for a developer to put their applications to 'sleep' while other programs run, and then to 'awaken' them just as quickly? In our own program, we might do something as crude as detecting when the user has been idle (no mouse motion or key press) for (say) four seconds: var idle_id:uint = setInterval(4000, pause_program); var current_movie_clip:MovieClip; var current_frame:uint; ... // on Mouse move or key press... clearInterval(idle_id); idle_id = setInterval(4000, pause_program); ... function pause_program():void { current_movie_clip = event.target as MovieClip; current_frame = current_movie_clip.currentFrame; MovieClip(root).gotoAndStop("program_pause_screen"); } (on the program pause screen) resume_button.addEventListener(MouseEvent.CLICK, resume_program); function resume_program(event:MouseEvent) { current_movie_clip.gotoAndPlay(current_frame); } If that's the right idea, what's the best way to detect that an application should be shelved? And, more importantly, is it possible for Flash Player to detect that some of its running programs are idle, and to similarly shelve them until the user performs an action to resume them? (Please feel free to answer as much or as little of the many questions I've posed.)

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  • Hidden Features of PHP?

    - by George Mauer
    EDIT: This didn't really start as a hidden features of PHP topic, but thats what it ended up as, so go nuts. I know this sounds like a point-whoring question but let me explain where I'm coming from. Out of college I got a job at a PHP shop. I worked there for a year and a half and thought that I had learned all there was to learn about programming. Then I got a job as a one-man internal development shop at a sizable corporation where all the work was in C#. In my commitment to the position I started reading a ton of blogs and books and quickly realized how wrong I was to think I knew everything. I learned about unit testing, dependency injection and decorator patterns, the design principle of loose coupling, the composition over inheritance debate, and so on and on and on - I am still very much absorbing it all. Needless to say my programming style has changed entirely in the last year. Now I find myself picking up a php project doing some coding for a friend's start-up and I feel completely constrained as opposed to programming in C#. It really bothers me that all variables at a class scope have to be referred to by appending '$this-' . It annoys me that none of the IDEs that I've tried have very good intellisense and that my SimpleTest unit tests methods have to start with the word 'test'. It drives me crazy that dynamic typing keeps me from specifying implicitly which parameter type a method expects, and that you have to write a switch statement to do method overloads. I can't stand that you can't have nested namespaces and have to use the :: operator to call the base class's constructor. Now I have no intention of starting a PHP vs C# debate, rather what I mean to say is that I'm sure there are some PHP features that I either don't know about or know about yet fail to use properly. I am set in my C# universe and having trouble seeing outside the glass bowl. So I'm asking, what are your favorite features of PHP? What are things you can do in it that you can't or are more difficult in the .Net languages?

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  • passing multiple vectors to function by reference (using structure)

    - by madman
    Hi StackOverflow, Can someone tell me the correct way of passing multiple vectors to a function that can take only a single argument? (specifically for pthread_create (..) function) I tried the following but it does not seem to work :-( First, I created the following structure struct ip2 { void* obj; int dim; int n_s; vector<vector<vector<double> > > *wlist; vector<int> *nrsv; struct model *pModel; }; The threads that I have created actually needs all these parameters. Since im using pthreads_create I put all this in a structure and then passed the pointer to the structure as an argument to pthread_create (as shown). some_fxn() { //some code struct ip2 ip; ip.obj=(void*) this; ip.n_s=n_s; ip.wlist=&wlist; ip.nrsv=&nrsv; ip.pModel=pModel; ip.dim=dim; pthread_create(&callThd1[lcntr], &attr1, &Cls::Entry, (void*) &ip); } The Entry method looks something like this. void* Cls::Entry(void *ip) { struct ip2 *x; x = (struct ip2 *)ip; (reinterpret_cast<Cls1 *>(x->obj))->Run(x->dim,x->n_s, x->wlist, x->nrsv, x->pModel); } The Run method looks something like this. void Run(int dim, int n_c, vector<vector<vector<double> > > *wlist, vector<int> *nrsv, struct model* pModel ) { //some code for(int k = 0; k < n_c; ++k) { //some code end = index + nrsv[k]; //some code } I get the following error when I try to compile the program. error: no match for ‘operator+’ in ‘index + *(((std::vector<int, std::allocator<int> >*)(((unsigned int)k) * 12u)) + nrsv)’ Can someone tell me how to do it the right way. Madhavan

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  • Using array as map value: Cant see the error

    - by Tom
    Hi all, Im trying to create a map, where the key is an int, and the value is an array int red[3] = {1,0,0}; int green[3] = {0,1,0}; int blue[3] = {0,0,1}; std::map<int, int[3]> colours; colours.insert(std::pair<int,int[3]>(GLUT_LEFT_BUTTON,red)); //THIS IS LINE 24 ! colours.insert(std::pair<int,int[3]>(GLUT_MIDDLE_BUTTON,blue)); colours.insert(std::pair<int,int[3]>(GLUT_RIGHT_BUTTON,green)); However, when I try to compile this code, I get the following error. g++ (Ubuntu 4.4.1-4ubuntu8) 4.4.1 In file included from /usr/include/c++/4.4/bits/stl_algobase.h:66, from /usr/include/c++/4.4/bits/stl_tree.h:62, from /usr/include/c++/4.4/map:60, from ../src/utils.cpp:9: /usr/include/c++/4.4/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _T1 = int, _T2 = int [3]]’: ../src/utils.cpp:24: instantiated from here /usr/include/c++/4.4/bits/stl_pair.h:84: error: array used as initializer /usr/include/c++/4.4/bits/stl_pair.h: In constructor ‘std::pair<_T1, _T2>::pair(const std::pair<_U1, _U2>&) [with _U1 = int, _U2 = int [3], _T1 = const int, _T2 = int [3]]’: ../src/utils.cpp:24: instantiated from here /usr/include/c++/4.4/bits/stl_pair.h:101: error: array used as initializer In file included from /usr/include/c++/4.4/map:61, from ../src/utils.cpp:9: /usr/include/c++/4.4/bits/stl_map.h: In member function ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = int, _Tp = int [3], _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, int [3]> >]’: ../src/utils.cpp:30: instantiated from here /usr/include/c++/4.4/bits/stl_map.h:450: error: conversion from ‘int’ to non-scalar type ‘int [3]’ requested make: *** [src/utils.o] Error 1 I really cant see where the error is. Or even if there's an error. Any help (please include an explanation to help me avoid this mistake) will be appreciated. Thanks in advance.

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  • How to create JPA EntityMananger in Spring Context?

    - by HDave
    I have a JPA/Spring application that uses Hibernate as the JPA provider. In one portion of the code, I have to manually create a DAO in my application with the new operator rather than use Spring DI. When I do this, the @PersistenceContext annotation is not processed by Spring. In my code where I create the DAO I have an EntityManagerFactory which I used to set the entityManager as follows: @PersistenceUnit private EntityManagerFactory entityManagerFactory; MyDAO dao = new MyDAOImpl(); dao.setEntityManager(entityManagerFactory.createEntityManager()); The problem is that when I do this, I get a Hibernate error: Could not find UserTransaction in JNDI [java:comp/UserTransaction] It's as if the HibernateEntityManager never received all the settings I've configured in Spring: <bean id="myAppTestLocalEmf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="persistenceUnitName" value="myapp-core" /> <property name="persistenceUnitPostProcessors"> <bean class="com.myapp.core.persist.util.JtaPersistenceUnitPostProcessor"> <property name="jtaDataSource" ref="myappPersistTestJdbcDataSource" /> </bean> </property> <property name="jpaProperties"> <props> <prop key="hibernate.transaction.factory_class">org.hibernate.transaction.JTATransactionFactory</prop> <prop key="hibernate.transaction.manager_lookup_class">com.atomikos.icatch.jta.hibernate3.TransactionManagerLookup</prop> </props> </property> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="showSql" value="true" /> <!-- The following use the PropertyPlaceholderConfigurer but it doesn't work in Eclipse --> <property name="database" value="$DS{hibernate.database}" /> <property name="databasePlatform" value="$DS{hibernate.dialect}" /> I am not sure, but I think the issue might be that I am not creating the entity manager correctly with the plain vanilla createEntityManager() call rather than passing in a map of properties. I say this because when Spring's LocalContainerEntityManagerFactoryBean proxy's the call to Hibernate's createEntityManager() all of the Spring configured options are missing. That is, there is no Map argument to the createEntityManager() call. Perhaps it is another problem entirely however....not sure!

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  • indentationLevelForRowAtIndexPath not indenting custom cell

    - by Xetius
    I have overridden the tableView:indentationLevelForRowAtIndexPath method in my UITableViewController derived class as follows: - (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath { NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; int indentationLevel = [[item objectForKey:@"indent"] intValue]; DLog (@"Indentation Level for Row %d : %d", indexPath.row, indentationLevel); return indentationLevel; } I initially thought that this was not being called but that was operator error (err, mine) and I hadn't defined the symbol DEBUG=1. However, it is being called (duh me!) and this is the log output: -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 0 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 1 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 2 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 3 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 4 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 5 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 6 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 7 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 8 : 1 But, this is not affecting the layout of the cells. No indentation. This is my itemCellForRowAtIndexPath implementation, if that makes any difference: -(UITableViewCell*)tableView:(UITableView *)tableView itemCellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString* cellIdentifier = @"projectItemCell"; ProjectItemTableViewCell* cell = (ProjectItemTableViewCell*)[tableView dequeueReusableCellWithIdentifier:cellIdentifier]; if (cell == nil) { NSArray* nib = [[NSBundle mainBundle] loadNibNamed:@"ProjectItemTableViewCell" owner:self options:nil]; for (id oneObject in nib) { if ([oneObject isKindOfClass:[ProjectItemTableViewCell class]]) { cell = (ProjectItemTableViewCell*)oneObject; } } } NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; cell.projectDescLabel.text = [item objectForKey:@"name"]; cell.itemCountlabel.text = [NSString stringWithFormat:@"%d", [[item objectForKey:@"cache_count"] intValue]]; cell.itemCountlabel.backgroundColor = [UIColor colorForHex:[item objectForKey:@"color"]]; cell.indentationWidth = 20; return cell; } How do I indent a custom UITableViewCell which I have defined in Interface Builder? If I change the itemCellForRowAtIndexPath to use a default UITableViewCell with the code below, then it indents fine. static NSString* cellIdentifier = @"projectItemCell"; UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease]; } NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; cell.textLabel.text = [item objectForKey:@"name"]; cell.indentationWidth = 40; return cell;

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  • compiling opencv 2.4 on a 64 bit mac in Xcode

    - by Walt
    I have an opencv project that I've been developing under ubuntu 12.04, on a parellels VM on a mac which has an x86_64 architecture. There have been many screen switching performance issues that I believe are due to the VM, where linux video modes flip around for a couple seconds while camera access is made by the opencv application. I decided to moved the project into Xcode on the mac side of the computer to continue the opencv development. However, I'm not that familiar with xcode and am having trouble getting the project to build correctly there. I have xcode installed. I downloaded and decompressed the latest version of opencv on the mac, and ran: ~/src/opencv/build/cmake-gui -G Xcode .. per the instructions from willowgarage and various other locations. This appeared to work fine (however I'm wondering now if I'm missing an architecture setting in here, although it is 64-bit intel in Xcode). I then setup an xcode project with the source files from the linux project and changed the include directories to use /opt/local/include/... rather than the /usr/local/include/... I switched xcode to use the LLVM GCC compiler in the build settings for the project then set the Apple LLVM Dialog for C++ to Language Dialect to GNU++11 (which seems possibly inconsistant with the line above) I'm not using a makefile in xcode, (that I'm aware of - it has its own project file...) I was also running into a linker issue that looked like they may be resolved with the addition of this linker flag: -lopencv_video based on a similar posting here: other thread however in that case the person was using a Makefile in their project. I've tried adding this linker flag under "Other Linker Flags" in xcode build settings but still get build errors. I think I may have two issues here, one with the architecture settings when building the opencv libraries with Cmake, and one with the linker flag settings in my project. Currently the build error list looks like this: Undefined symbols for architecture x86_64: "cv::_InputArray::_InputArray(cv::Mat const&)", referenced from: _main in main.o "cv::_OutputArray::_OutputArray(cv::Mat&)", referenced from: _main in main.o "cv::Mat::deallocate()", referenced from: cv::Mat::release() in main.o "cv::Mat::copySize(cv::Mat const&)", referenced from: cv::Mat::Mat(cv::Mat const&)in main.o cv::Mat::operator=(cv::Mat const&)in main.o "cv::Mat::Mat(_IplImage const*, bool)", referenced from: _main in main.o "cv::imread(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)", referenced from: _main in main.o ---SNIP--- ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status Can anyone provide some guidance on what to try next? Thanks, Walt

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  • Dynamic Linq help, different errors depending on object passed as parameter?

    - by sah302
    I have an entityDao that is inherbited by everyone of my objectDaos. I am using Dynamic Linq and trying to get some generic queries to work. I have the following code in my generic method in my EntityDao : public abstract class EntityDao<ImplementationType> where ImplementationType : Entity { public ImplementationType getOneByValueOfProperty(string getProperty, object getValue){ ImplementationType entity = null; if (getProperty != null && getValue != null) { LCFDataContext lcfdatacontext = new LCFDataContext(); //Generic LINQ Query Here entity = lcfdatacontext.GetTable<ImplementationType>().Where(getProperty + " =@0", getValue).FirstOrDefault(); //.Where(getProperty & "==" & CStr(getValue)) } //lcfdatacontext.SubmitChanges() //lcfdatacontext.Dispose() return entity; } }         Then I do the following method call in a unit test (all my objectDaos inherit entityDao): [Test] public void getOneByValueOfProperty() { Accomplishment result = accomplishmentDao.getOneByValueOfProperty("AccomplishmentType.Name", "Publication"); Assert.IsNotNull(result); } The above passes (AccomplishmentType has a relationship to accomplishment) Accomplishment result = accomplishmentDao.getOneByValueOfProperty("Description", "Can you hear me now?"); Accomplishment result = accomplishmentDao.getOneByValueOfProperty("LocalId", 4); Both of the above work Accomplishment result = accomplishmentDao.getOneByValueOfProperty("Id", New Guid("95457751-97d9-44b5-8f80-59fc2d170a4c"))       Does not work and says the following: Operator '=' incompatible with operand types 'Guid' and 'Guid Why is this happening? Guid's can't be compared? I tried == as well but same error. What's even moreso confusing is that every example of Dynamic Linq I have seen simply usings strings whether using the parameterized where predicate or this one I have commented out: //.Where(getProperty & "==" & CStr(getValue)) With or without the Cstr, many datatypes don't work with this format. I tried setting the getValue to a string instead of an object as well, but then I just get different errors (such as a multiword string would stop comparison after the first word). What am I missing to make this work with GUIDs and/or any data type? Ideally I would like to be able to just pass in a string for getValue (as I have seen for every other dynamic LINQ example) instead of the object and have it work regardless of the data Type of the column.

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  • Running same powershell script multiple asynchronous times with separate runspace

    - by teqnomad
    Hi, I have a powershell script which is called by a batch script which is called by Trap Receiver (which also passes environment variables) (running on windows 2008). The traps are flushed out at times in sets of 2-4 trap events, and the batch script will echo the trap details for each message to a logfile, but the powershell script on the next line of the batch script will only appear to process the first trap message (the powershell script writes to the same logfile). My interpetation is that the defaultrunspace is common to all iterations of the script running and this is why the others appear to be ignored. I've tried adding "-sta" when I invoke the powershell script using "powershell.exe -command", but this didn't help. I've researched and found a method using C# but I don't know this language, and busy enough learning powershell, so hoping to find a more direct solution especially as interleaving a "wrapper" between batch and powershell will involve passing the environment variables. http://www.codeproject.com/KB/threads/AsyncPowerShell.aspx I've hunted through stackoverflow, and again the only question of similar vein was using C#. Any suggestions welcome. Some script background: The powershell script is actually a modification of a great script found at gregorystrike website - cant post the link as I'm limited to one link but its the one for Lefthand arrays. Lots of mods so it can do multiple targets from one .ini file, taking in the environment variables, and options to run portions of the script interactively with winform. But you can see the gist of the original script. The batch script is pretty basic. The keys things are I'm trying to filter out trap noise using the :~ operator, and I tried -sta option to see if this would compartmentalise the powershell script. set debug=off set CMD_LINE_ARGS="%*" set LHIPAddress="%2" set VARBIND8="%8" shift shift shift shift shift shift shift set CHASSIS="%9" echo %DATE% %TIME% "Trap Received: %LHIPAddress% %CHASSIS% %VARBIND8%" >> C:\Logs\trap_out.txt set ACTION="%VARBIND8:~39,18%" echo %DATE% %TIME% "Action substring is %ACTION%" 2>&1 >> C:\Logs\trap_out.txt if %ACTION%=="Remote Copy Volume" ( echo Prepostlefthand_env_v2.9 >> C:\Logs\trap_out.txt c:\Windows\System32\WindowsPowerShell\v1.0\PowerShell.exe -sta -executionpolicy unrestricted -command " & 'C:\Scripts\prepostlefthand_env_v2.9.ps1' Backupsettings.ini ALL" 2>&1 >> C:\Logs\trap_out.txt ) ELSE ( echo %DATE% %TIME% Action substring is %ACTION% so exiting" 2>&1 >> C:\Logs\trap.out.txt ) exit

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  • Iterator failure while moving over equal_range in Boost MultiIndex container

    - by Sarah
    I'm making some mistake with my iterators, but I can't see it yet. I have a Boost MultiIndex container, HostContainer hmap, whose elements are boost::shared_ptr to members of class Host. All the indices work on member functions of class Host. The third index is by Host::getHousehold(), where the household member variable is an int. Below, I'm trying to iterate over the range of Hosts matching a particular household (int hhold2) and load the corresponding private member variable Host::id into an array. I'm getting an "Assertion failed: (px != 0), function operator-, file /Applications/boost_1_42_0/boost/smart_ptr/shared_ptr.hpp, line 418" error in runtime when the household size is 2. (I can't yet tell if it happens anytime the household size is 2, or if other conditions must be met.) typedef multi_index_container< boost::shared_ptr< Host >, indexed_by< hashed_unique< const_mem_fun<Host,int,&Host::getID> >, // 0 - ID index ordered_non_unique< const_mem_fun<Host,int,&Host::getAgeInY> >, // 1 - Age index ordered_non_unique< const_mem_fun<Host,int,&Host::getHousehold> > // 2 - Household index > // end indexed_by > HostContainer; typedef HostContainer::nth_index<2>::type HostsByHH; // inside main() int numFamily = hmap.get<2>().count( hhold2 ); int familyIDs[ numFamily ]; for ( int f = 0; f < numFamily; f++ ) { familyIDs[ f ] = 0; } int indID = 0; int f = 0; std::pair< HostsByHH::iterator, HostsByHH::iterator pit = hmap.get<2().equal_range( hhold2 ); cout << "\tNeed to update households of " << numFamily << " family members (including self) of host ID " << hid2 << endl; while ( pit.first != pit.second ) { cout << "Pointing at new family member still in hhold " << ((pit.first))-getHousehold() << "; " ; indID = ((pit.first) )-getID(); familyIDs[ f ] = indID; pit.first++; f++; } What could make this code fail? The above snippet only runs when numFamily 1. (Other suggestions and criticisms are welcome too.) Thank you in advance.

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  • How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

    - by Ian Ringrose
    We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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  • What is the proper use of boost::fusion::push_back?

    - by Kyle
    // ... snipped includes for iostream and fusion ... namespace fusion = boost::fusion; class Base { protected: int x; public: Base() : x(0) {} void chug() { x++; cout << "I'm a base.. x is now " << x << endl; } }; class Alpha : public Base { public: void chug() { x += 2; cout << "Hi, I'm an alpha, x is now " << x << endl; } }; class Bravo : public Base { public: void chug() { x += 3; cout << "Hello, I'm a bravo; x is now " << x << endl; } }; struct chug { template<typename T> void operator()(T& t) const { t->chug(); } }; int main() { typedef fusion::vector<Base*, Alpha*, Bravo*, Base*> Stuff; Stuff stuff(new Base, new Alpha, new Bravo, new Base); fusion::for_each(stuff, chug()); // Mutates each element in stuff as expected /* Output: I'm a base.. x is now 1 Hi, I'm an alpha, x is now 2 Hello, I'm a bravo; x is now 3 I'm a base.. x is now 1 */ cout << endl; // If I don't put 'const' in front of Stuff... typedef fusion::result_of::push_back<const Stuff, Alpha*>::type NewStuff; // ... then this complains because it wants stuff to be const: NewStuff newStuff = fusion::push_back(stuff, new Alpha); // ... But since stuff is now const, I can no longer mutate its elements :( fusion::for_each(newStuff, chug()); return 0; }; How do I get for_each(newStuff, chug()) to work? (Note: I'm only assuming from the overly brief documentation on boost::fusion that I am supposed to create a new vector every time I call push_back.)

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  • G++, compiler warnings, c++ templates

    - by Ian
    During the compilatiion of the C++ program those warnings appeared: c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bc:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2317: instantiated from `void std::partial_sort(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2506: instantiated from `void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Size = int, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2589: instantiated from `void std::sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' io/../structures/objects/../../algorithm/analysis/../../structures/list/ObjectsList.hpp:141: instantiated from `void ObjectsList <T>::sortObjects(unsigned int, T, T, T, T, unsigned int) [with T = double]' I do not why, because all objects have only template parameter T, their local variables are also T. The only place, where I am using double is main. There are objects of type double creating and adding into the ObjectsList... Object <double> o1; ObjectsList <double> olist; olist.push_back(o1); .... T xmin = ..., ymin = ..., xmax = ..., ymax = ...; unsigned int n = ...; olist.sortAllObjects(xmin, ymin, xmax, ymax, n); and comparator template <class T> class sortObjects { private: unsigned int n; T xmin, ymin, xmax, ymax; public: sortObjects ( const T xmin_, const T ymin_, const T xmax_, const T ymax_, const int n_ ) : xmin ( xmin_ ), ymin ( ymin_ ), xmax ( xmax_ ), ymax ( ymax_ ), n ( n_ ) {} bool operator() ( const Object <T> *o1, const Object <T> *o2 ) const { T dmax = (std::max) ( xmax - xmin, ymax - ymin ); T x_max = ( xmax - xmin ) / dmax; T y_max = ( ymax - ymin ) / dmax; ... return ....; } representing ObjectsList method: template <class T> void ObjectsList <T> ::sortAllObjects ( const T xmin, const T ymin, const T xmax, const T ymax, const unsigned int n ) { std::sort ( objects.begin(), objects.end(), sortObjects <T> ( xmin, ymin, xmax, ymax, n ) ); }

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  • Postgresql: Implicit lock acquisition from foreign-key constraint evaluation

    - by fennec
    So, I'm being confused about foreign key constraint handling in Postgresql. (version 8.4.4, for what it's worth). We've got a couple of tables, mildly anonymized below: device: (id, blah, blah, blah, blah, blah x 50)… primary key on id whooooole bunch of other junk device_foo: (id, device_id, left, right) Foreign key (device_id) references device(id) on delete cascade; primary key on id btree index on 'left' and 'right' So I set out with two database windows to run some queries. db1> begin; lock table device in exclusive mode; db2> begin; update device_foo set left = left + 1; The db2 connection blocks. It seems odd to me that an update of the 'left' column on device_stuff should be affected by activity on the device table. But it is. In fact, if I go back to db1: db1> select * from device_stuff for update; *** deadlock occurs *** The pgsql log has the following: blah blah blah deadlock blah. CONTEXT: SQL statement "SELECT 1 FROM ONLY "public"."device" x WHERE "id" OPERATOR(pg_catalog.=) $1 FOR SHARE OF X: update device_foo set left = left + 1; I suppose I've got two issues: the first is that I don't understand the precise mechanism by which this sort of locking occurs. I have got a couple of useful queries to query pg_locks to see what sort of locks a statement invokes, but I haven't been able to observe this particular sort of locking when I run the update device_foo command in isolation. (Perhaps I'm doing something wrong, though.) I also can't find any documentation on the lock acquisition behavior of foreign-key constraint checks. All I have is a log message. Am I to infer from this that any change to a row will acquire an update lock on all the tables which it's foreign-keyed against? The second issue is that I'd like to find some way to make it not happen like that. I'm ending up with occasional deadlocks in the actual application. I'd like to be able to run big update statements that impact all rows on device_foo without acquiring a big lock on the device table. (There's a lot of access going on in the device table, and it's kind of an expensive lock to get.)

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  • std::ostream interface to an OLE IStream

    - by PaulH
    I have a Visual Studio 2008 C++ application using IStreams. I would like to use the IStream connection in a std::ostream. Something like this: IStream* stream = /*create valid IStream instance...*/; IStreamBuf< WIN32_FIND_DATA > sb( stream ); std::ostream os( &sb ); WIN32_FIND_DATA d = { 0 }; // send the structure along the IStream os << d; To accomplish this, I've implemented the following code: template< class _CharT, class _Traits > inline std::basic_ostream< _CharT, _Traits >& operator<<( std::basic_ostream< _CharT, _Traits >& os, const WIN32_FIND_DATA& i ) { const _CharT* c = reinterpret_cast< const _CharT* >( &i ); const _CharT* const end = c + sizeof( WIN32_FIND_DATA ) / sizeof( _CharT ); for( c; c < end; ++c ) os << *c; return os; } template< typename T > class IStreamBuf : public std::streambuf { public: IStreamBuf( IStream* stream ) : stream_( stream ) { setp( reinterpret_cast< char* >( &buffer_ ), reinterpret_cast< char* >( &buffer_ ) + sizeof( buffer_ ) ); }; virtual ~IStreamBuf() { sync(); }; protected: traits_type::int_type FlushBuffer() { int bytes = std::min< int >( pptr() - pbase(), sizeof( buffer_ ) ); DWORD written = 0; HRESULT hr = stream_->Write( &buffer_, bytes, &written ); if( FAILED( hr ) ) { return traits_type::eof(); } pbump( -bytes ); return bytes; }; virtual int sync() { if( FlushBuffer() == traits_type::eof() ) return -1; return 0; }; traits_type::int_type overflow( traits_type::int_type ch ) { if( FlushBuffer() == traits_type::eof() ) return traits_type::eof(); if( ch != traits_type::eof() ) { *pptr() = ch; pbump( 1 ); } return ch; }; private: /// data queued up to be sent T buffer_; /// output stream IStream* stream_; }; // class IStreamBuf Yes, the code compiles and seems to work, but I've not had the pleasure of implementing a std::streambuf before. So, I'd just like to know if it's correct and complete. Thanks, PaulH

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  • In Ruby, how does coerce() actually work?

    - by Jian Lin
    It is said that when we have a class Point and knows how to perform point * 3 like the following: class Point def initialize(x,y) @x, @y = x, y end def *(c) Point.new(@x * c, @y * c) end end point = Point.new(1,2) p point p point * 3 Output: #<Point:0x336094 @x=1, @y=2> #<Point:0x335fa4 @x=3, @y=6> but then, 3 * point is not understood: Point can't be coerced into Fixnum (TypeError) So we need to further define an instance method coerce: class Point def coerce(something) [self, something] end end p 3 * point Output: #<Point:0x3c45a88 @x=3, @y=6> So it is said that 3 * point is the same as 3.*(point) that is, the instance method * takes an argument point and invoke on the object 3. Now, since this method * doesn't know how to multiply a point, so point.coerce(3) will be called, and get back an array: [point, 3] and then * is once again applied to it, is that true? point * 3 which is the same as point.*(3) and now, this is understood and we now have a new Point object, as performed by the instance method * of the Point class. The question is: 1) who invokes point.coerce(3) ? Is it Ruby automatically, or is it some code inside of * method of Fixnum by catching an exception? Or is it by case statement that when it doesn't know one of the known types, then call coerce? 2) Does coerce always need to return an array of 2 elements? Can it be no array? Or can it be an array of 3 elements? 3) And is the rule that, the original operator (or method) * will then be invoked on element 0, with the argument of element 1? (element 0 and element 1 are the two elements in that array returned by coerce) Who does it? Is it done by Ruby or is it done by code in Fixnum? If it is done by code in Fixnum, then it is a "convention" that everybody follows when doing a coerce? So could it be the code in * of Fixnum do something like this: if (something.typeof? ...) else if ... # other type else if ... # other type else # if it is not a type I know array = something.coerce(self) return array[0].*(array[1]) end

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  • Using a map with set_intersection

    - by Robin Welch
    Not used set_intersection before, but I believe it will work with maps. I wrote the following example code but it doesn't give me what I'd expect: #include <map> #include <string> #include <iostream> #include <algorithm> using namespace std; struct Money { double amount; string currency; bool operator< ( const Money& rhs ) const { if ( amount != rhs.amount ) return ( amount < rhs.amount ); return ( currency < rhs.currency ); } }; int main( int argc, char* argv[] ) { Money mn[] = { { 2.32, "USD" }, { 2.76, "USD" }, { 4.30, "GBP" }, { 1.21, "GBP" }, { 1.37, "GBP" }, { 6.74, "GBP" }, { 2.55, "EUR" } }; typedef pair< int, Money > MoneyPair; typedef map< int, Money > MoneyMap; MoneyMap map1; map1.insert( MoneyPair( 1, mn[1] ) ); map1.insert( MoneyPair( 2, mn[2] ) ); map1.insert( MoneyPair( 3, mn[3] ) ); // (3) map1.insert( MoneyPair( 4, mn[4] ) ); // (4) MoneyMap map2; map1.insert( MoneyPair( 3, mn[3] ) ); // (3) map1.insert( MoneyPair( 4, mn[4] ) ); // (4) map1.insert( MoneyPair( 5, mn[5] ) ); map1.insert( MoneyPair( 6, mn[6] ) ); map1.insert( MoneyPair( 7, mn[7] ) ); MoneyMap out; MoneyMap::iterator out_itr( out.begin() ); set_intersection( map1.begin(), map1.end(), map2.begin(), map2.end(), inserter( out, out_itr ) ); cout << "intersection has " << out.size() << " elements." << endl; return 0; } Since the pair labelled (3) and (4) appear in both maps, I was expecting that I'd get 2 elements in the intersection, but no, I get: intersection has 0 elements. I'm sure this is something to do with the comparitor on the map / pair but can't figure it out.

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