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• Java EE javax.xml.bind.MarshalException

  - by sandeep

  Hi, I am getting javax.xml.bind.MarshalException error. I am sending List from my webservice to the backingbean and I have this error. WARNING: invocation error on ejb endpoint Login_webservice at /Login_webserviceService/Login_webservice : javax.xml.bind.MarshalException - with linked exception: [javax.xml.bind.JAXBException: class JPA.Cantable nor any of its super class is known to this context.] javax.xml.ws.WebServiceException: javax.xml.bind.MarshalException - with linked exception: [javax.xml.bind.JAXBException: class JPA.Cantable nor any of its super class is known to this context.] at com.sun.xml.ws.message.jaxb.JAXBMessage.writePayloadTo(JAXBMessage.java:325) at com.sun.xml.ws.message.AbstractMessageImpl.writeTo(AbstractMessageImpl.java:142) at com.sun.xml.ws.encoding.StreamSOAPCodec.encode(StreamSOAPCodec.java:109) at com.sun.xml.ws.encoding.SOAPBindingCodec.encode(SOAPBindingCodec.java:278) at com.sun.xml.ws.transport.http.HttpAdapter.encodePacket(HttpAdapter.java:380) at com.sun.xml.ws.transport.http.HttpAdapter.access$100(HttpAdapter.java:92) at com.sun.xml.ws.transport.http.HttpAdapter$HttpToolkit.handle(HttpAdapter.java:525) at com.sun.xml.ws.transport.http.HttpAdapter.handle(HttpAdapter.java:285) at com.sun.xml.ws.transport.http.servlet.ServletAdapter.handle(ServletAdapter.java:143) at org.glassfish.webservices.Ejb3MessageDispatcher.handlePost(Ejb3MessageDispatcher.java:116) at org.glassfish.webservices.Ejb3MessageDispatcher.invoke(Ejb3MessageDispatcher.java:87) at org.glassfish.webservices.EjbWebServiceServlet.dispatchToEjbEndpoint(EjbWebServiceServlet.java:196) at org.glassfish.webservices.EjbWebServiceServlet.service(EjbWebServiceServlet.java:127) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) Here is my code: Backing bean @WebServiceRef(wsdlLocation = "http://localhost:26565/Login_webserviceService/Login_webservice?WSDL") public String login() { System.out.println("Login Phase entered"); int result = 0; List list; List finalList = null; try { Weblogin.LoginWebserviceService service = new Weblogin.LoginWebserviceService(); Weblogin.LoginWebservice port = service.getLoginWebservicePort(); result = port.login(voterID, password); Weblogin.LoginWebservice port1 = service.getLoginWebservicePort(); list = port1.candDetails(1); finalList = list; this.setList(finalList); } catch (Exception e) { e.printStackTrace(); } if (result == 1) return "polling"; else return "login"; } Webservice public List candDetails(int pollEvent) { List resultList = null; List finalList = null; try { if (pollEvent == 1) { resultList = em.createNamedQuery("Cantable.findAll").getResultList(); finalList = resultList; } } catch (Exception e) { e.printStackTrace(); } return resultList; }

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• MinGW error "undefined reference to 'typeof''"

  - by DSblizzard

  Code: #include <stdio.h> #include <stdlib.h> #include <stddef.h> int main() { typeof(5); return 0; } Version of gcc is 4.3.3, command line is "gcc.exe -std=c99 1.c -o 1.exe". What is the cause of this problem?

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• "range of" in if condition C programming

  - by Samantha

  Hello, I'm working on a simple C prorgam, and i'ms tuck with an if test: int line_number = 0; if ((line_number >= argv[2]) && (line_number <= argv[4]) ) gcc says: cp.c:25: warning: comparison between pointer and integer cp.c:25: warning: comparison between pointer and integer What can I do to properly write the range of line I want to deal with ? Thank you!

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• SEAM nagivation based on function with parameters

  - by John

  How do you setup a navigation rule based on a function with parameters in SEAM ? For example <page view-id="/firstPage.xhtml" back="enabled"> <navigation from-action="#{actionBean.fetchItem(int index)}"> <redirect view-id="/itemDetail.xhtml" /> </navigation> </page> Thanks

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• Why is it useful to count the number of bits?

  - by Scorchin

  I've seen the numerous questions about counting the number of set bits in a insert type of input, but why is it useful? For those looking for algorithms about bit counting, look here: http://stackoverflow.com/questions/1517848/counting-common-bits-in-a-sequence-of-unsigned-longs http://stackoverflow.com/questions/472325/fastest-way-to-count-number-of-bit-transitions-in-an-unsigned-int http://stackoverflow.com/questions/109023/best-algorithm-to-count-the-number-of-set-bits-in-a-32-bit-integer

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• SSE SIMD Optimization For Loop

  - by Projectile Fish

  I have some code in a loop for(int i = 0; i < n; i++) { u[i] = c * u[i] + s * b[i]; } So, u and b are vectors of the same length, and c and s are scalars. Is this code a good candidate for vectorization for use with SSE in order to get a speedup?

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• Why use infinite loops?

  - by Moishe

  Another poster asked about preferred syntax for infinite loops. A follow-up question: Why do you use infinite loops in your code? I typically see a construct like this: for (;;) { int scoped_variable = getSomeValue(); if (scoped_variable == some_value) { break; } } Which lets you get around not being able to see the value of scoped_variable in the for or while clause. What are some other uses for "infinite" loops?

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• How do I get the PreviewDialog of Apache FOP to actually display my document?

  - by JRSofty

  Search as I may I have not found a solution to my problem here and I'm hoping the combined minds of StackOverflow will push me in the right direction. My problem is as follows, I'm developing a print and print preview portion of a messaging system's user agent. I was given specific XSLT templates that after transforming XML will produce a Formatting Objects document. With Apache FOP I've been able to render the FO document into PDF which is all fine and good, but I would also like to display it in a print preview dialog. Apache FOP contains such a class called PreviewDialog which requires in its constructor a FOUserAgent, which I can generate, and an object implementing the Renderable Interface. The Renderable Interface has one implementing class in the FOP package which is called InputHandler which takes in its constructor a standard io File object. Now here is where the trouble begins. I'm currently storing the FO document as a temp file and pass this as a File object to an InputHandler instance which is then passed to the PreviewDialog. I see the dialog appear on my screen and along the bottom in a status bar it says that it is generating the document, and that is all it does. Here is the code I'm trying to use. It isn't production code so it's not pretty: import java.io.BufferedOutputStream; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.util.Random; import javax.xml.transform.Result; import javax.xml.transform.Source; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerConfigurationException; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.sax.SAXResult; import javax.xml.transform.stream.StreamResult; import javax.xml.transform.stream.StreamSource; import org.apache.fop.apps.FOPException; import org.apache.fop.apps.FOUserAgent; import org.apache.fop.apps.Fop; import org.apache.fop.apps.FopFactory; import org.apache.fop.cli.InputHandler; import org.apache.fop.render.awt.viewer.PreviewDialog; public class PrintPreview { public void showPreview(final File xslt, final File xmlSource) { boolean err = false; OutputStream out = null; Transformer transformer = null; final String tempFileName = this.getTempDir() + this.generateTempFileName(); final String tempFoFile = tempFileName + ".fo"; final String tempPdfFile = tempFileName + ".pdf"; System.out.println(tempFileName); final TransformerFactory transformFactory = TransformerFactory .newInstance(); final FopFactory fopFactory = FopFactory.newInstance(); try { transformer = transformFactory .newTransformer(new StreamSource(xslt)); final Source src = new StreamSource(xmlSource); out = new FileOutputStream(tempFoFile); final Result res = new StreamResult(out); transformer.transform(src, res); System.out.println("XSLT Transform Completed"); } catch (final TransformerConfigurationException e) { err = true; e.printStackTrace(); } catch (final FileNotFoundException e) { err = true; e.printStackTrace(); } catch (final TransformerException e) { err = true; e.printStackTrace(); } finally { if (out != null) { try { out.close(); } catch (final IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } System.out.println("Initializing Preview"); transformer = null; out = null; final File fo = new File(tempFoFile); final File pdf = new File(tempPdfFile); if (!err) { final FOUserAgent ua = fopFactory.newFOUserAgent(); try { transformer = transformFactory.newTransformer(); out = new FileOutputStream(pdf); out = new BufferedOutputStream(out); final Fop fop = fopFactory.newFop( MimeConstants.MIME_PDF, ua, out); final Source foSrc = new StreamSource(fo); final Result foRes = new SAXResult(fop.getDefaultHandler()); transformer.transform(foSrc, foRes); System.out.println("Transformation Complete"); } catch (final FOPException e) { err = true; e.printStackTrace(); } catch (final FileNotFoundException e) { err = true; e.printStackTrace(); } catch (final TransformerException e) { err = true; e.printStackTrace(); } finally { if (out != null) { try { out.close(); } catch (final IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } if (!err) { System.out.println("Attempting to Preview"); final InputHandler inputHandler = new InputHandler(fo); PreviewDialog.createPreviewDialog(ua, inputHandler, true); } } // perform the clean up // f.delete(); } private String getTempDir() { final String p = "java.io.tmpdir"; return System.getProperty(p); } private String generateTempFileName() { final String charset = "abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890"; final StringBuffer sb = new StringBuffer(); Random r = new Random(); int seed = r.nextInt(); r = new Random(seed); for (int i = 0; i < 8; i++) { final int n = r.nextInt(71); seed = r.nextInt(); sb.append(charset.charAt(n)); r = new Random(seed); } return sb.toString(); } } Any help on this would be appreciated.

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• How to get parameter values for dm_exec_sql_text

  - by Ted Elliott

  I'm running the following statement to see what queries are executing in sql server: select * from sys.dm_exec_requests r cross apply sys.dm_exec_sql_text(r.sql_handle) where r.database_id = DB_ID('<dbname>') The sql text that comes back is parameterized: (@Parm0 int) select * from foo where foo_id = @Parm0 Is there any way to get the values for the parameters that the statement is using? Say by joining to another table perhaps?

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• Performance: Iterating through a List in Java

  - by syker

  Is it slower to iterate through a list in Java like this: for (int i=0;i<list.size();i++) { .. list.get(i) } as opposed to: for (Object o: list) { ... o }

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• sql server procedure error

  - by Mohan

  CREATE PROCEDURE USP_SEARCH_HOTELS ( @Text varchar(50), @Type varchar(40) ) AS BEGIN Declare @Query VARCHAR(60) IF @Type = 'By Country' BEGIN SET @Query = 'Hotel.countryName like '+ @Text+'%' END ELSE IF @Type = 'By State' BEGIN SET @Query = 'HOTEL.stateName like '+ @Text+'%' END ELSE IF @Type='By Property Name' BEGIN SET @Query='hotel.propertyname like'+ @Text+'%' End ELSE IF @Type='By Rating' BEGIN SET @Query='hotel.starRating='+ Cast(@Text as INT) END ELSE IF @Type='By City' BEGIN SET @Query='hotel.cityName like '+ @Text+'%' END begin select * from hotel,tbl_cust_info where hotel.agentID=Tbl_Cust_Info.Cust_ID and (@Query) end END WHAT IS THE ERROR IN THIS PROCEDURE PLEASE HELP.

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• How do char arrays work in C?

  - by eSKay

  #include<stdio.h> int main() { char a[5]="hello"; puts(a); //prints hello } Why does the code compile correctly? We need six places to store "hello", correct?

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• bin_at in dlmalloc

  - by chunhui

  In glibc malloc.c or dlmalloc It said "repositioning tricks"As in blew, and use this trick in bin_at. bins is a array,the space is allocated when av(struct malloc_state) is allocated.doesn't it? the sizeof(bin[i]) is less then sizeof(struct malloc_chunk*)? Who can describe this trick for me? I can't understand the bin_at macro.why they get the bins address use this method?how it works? Very thanks,and sorry for my poor English. /* To simplify use in double-linked lists, each bin header acts as a malloc_chunk. This avoids special-casing for headers. But to conserve space and improve locality, we allocate only the fd/bk pointers of bins, and then use repositioning tricks to treat these as the fields of a malloc_chunk*. */ typedef struct malloc_chunk* mbinptr; /* addressing -- note that bin_at(0) does not exist */ #define bin_at(m, i) \ (mbinptr) (((char *) &((m)->bins[((i) - 1) * 2])) \ - offsetof (struct malloc_chunk, fd)) The malloc_chunk struct like this: struct malloc_chunk { INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */ INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */ struct malloc_chunk* fd; /* double links -- used only if free. */ struct malloc_chunk* bk; /* Only used for large blocks: pointer to next larger size. */ struct malloc_chunk* fd_nextsize; /* double links -- used only if free. */ struct malloc_chunk* bk_nextsize; }; And the bin type like this: typedef struct malloc_chunk* mbinptr; struct malloc_state { /* Serialize access. */ mutex_t mutex; /* Flags (formerly in max_fast). */ int flags; #if THREAD_STATS /* Statistics for locking. Only used if THREAD_STATS is defined. */ long stat_lock_direct, stat_lock_loop, stat_lock_wait; #endif /* Fastbins */ mfastbinptr fastbinsY[NFASTBINS]; /* Base of the topmost chunk -- not otherwise kept in a bin */ mchunkptr top; /* The remainder from the most recent split of a small request */ mchunkptr last_remainder; /* Normal bins packed as described above */ mchunkptr bins[NBINS * 2 - 2]; /* Bitmap of bins */ unsigned int binmap[BINMAPSIZE]; /* Linked list */ struct malloc_state *next; #ifdef PER_THREAD /* Linked list for free arenas. */ struct malloc_state *next_free; #endif /* Memory allocated from the system in this arena. */ INTERNAL_SIZE_T system_mem; INTERNAL_SIZE_T max_system_mem; };

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• is this possible in java or any other programming language

  - by drake

  public abstract class Master { public void printForAllMethodsInSubClass() { System.out.println ("Printing before subclass method executes"); } } public class Owner extends Master { public void printSomething () { System.out.println ("This printed from Owner"); } public int returnSomeCals () { return 5+5; } } Without messing with methods of subclass...is it possible to execute printForAllMethodsInSubClass() before the method of a subclass gets executed?

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• Double Buffering for Game objects, what's a nice clean generic C++ way?

  - by Gary

  This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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• Does ROWLEX support SPARQL?

  - by salt2world

  Hello, Does ROWLEX support SPARQL? Does ROWLEX support SQL Server? Does ROWLEX act lik Joseki server? Where can I find more detail information regarding ROWLEX besides http://rowlex.nc3a.nato.int/HowToUse.aspx? Thank you in advance, Paul

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• Is this valid Java code? My teacher claims it is, but I'm really not so sure.

  - by Sergio Tapia

  Granted he didn't show us actual code here, just mentioned it, I found it extremely bizarre. For example, according to what he said this is valid Java: public class Person { String Name; int Age; { //These two braces just chilling together - VALID? :O } }

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• How to index BigDecimal values in Lucene 3.0.1

  - by Petteri Hietavirta

  I have some BigDecimal values which should be indexed for searching. Lucene has NumericField but it has setters only for long, double, float and int. I could store it as a String but then I would not benefit from NumericRangeQuery. How you have stored your BigDecimals? Any best practices to share?

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• Grails validateable not work for non-persistent domain class

  - by Hoàng Long

  I followed the instruction here: http://www.grails.org/doc/latest/guide/7.%20Validation.html and added into config.groovy: grails.validateable.classes = [liningtest.Warm'] Then added in src/groovy/Warm.groovy (it's a non-persistent domain class): package liningtest import org.codehaus.groovy.grails.validation.Validateable class Warm { String name; int happyCite; Warm(String n, int h) { this.name = n; this.happyCite = h; } static constraints = { name(size: 1..50) happyCite(min: 100) } } But it just doesn't work (both "blank false" & "size: 0..25") for the "hasErrors" function. It always returns false, even when the name is 25. Is this a Grails bug, if yes, is there any work-around? I'm using Grails 1.3.3 UPDATE: I have updated the simplified code. And now I know that constraint "size" can't be used with "blank", but still does not work. My test class in test/unit/liningtest/WarmTests.groovy package liningtest import grails.test.* class WarmTests extends GrailsUnitTestCase { protected void setUp() { super.setUp() } protected void tearDown() { super.tearDown() } void testSomething() { def w = new Warm('Hihi', 3) assert (w.happyCite == 3) assert (w.hasErrors() == true) } } And the error I got: <?xml version="1.0" encoding="UTF-8" ?> <testsuite errors="1" failures="0" hostname="evolus-50b0002c" name="liningtest.WarmTests" tests="1" time="0.062" timestamp="2010-12-16T04:07:47"> <properties /> <testcase classname="liningtest.WarmTests" name="testSomething" time="0.062"> <error message="No signature of method: liningtest.Warm.hasErrors() is applicable for argument types: () values: [] Possible solutions: hashCode()" type="groovy.lang.MissingMethodException">groovy.lang.MissingMethodException: No signature of method: liningtest.Warm.hasErrors() is applicable for argument types: () values: [] Possible solutions: hashCode() at liningtest.WarmTests.testSomething(WarmTests.groovy:18) </error> </testcase> <system-out><![CDATA[--Output from testSomething-- ]]></system-out> <system-err><![CDATA[--Output from testSomething-- ]]></system-err> </testsuite> UPDATE 2: When I don't use Unit test, but try to call hasErrors in the controller, it runs but return false value. (hasErrors return false with Warm('Hihi', 3) ). Does anyone has a clue?

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• Generating a readable colour from RGB?

  - by Joe Simpson

  Hi, I'm putting in a function which will allow a user to input a color (eg: purple) and it will change the look of their profile to be purple. It's interpreted from text into a 'Color' class which stores them inside itself as RGB numbers (int for red, one for green and other for blue). What i don't know how to do is logically turn these three numbers into another 3 which will make a readable colour. Can anyone help me on how to do this? Joe

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• How do I create a list or set object in a class in Python?

  - by Az

  For my project, the role of the Lecturer (defined as a class) is to offer projects to students. Project itself is also a class. I have some global dictionaries, keyed by the unique numeric id's for lecturers and projects that map to objects. Thus for the "lecturers" dictionary (currently): lecturer[id] = Lecturer(lec_name, lec_id, max_students) I'm currently reading in a white-space delimited text file that has been generated from a database. I have no direct access to the database so I haven't much say on how the file is formatted. Here's a fictionalised snippet that shows how the text file is structured. Please pardon the cheesiness. 0001 001 "Miyamoto, S." "Even Newer Super Mario Bros" 0002 001 "Miyamoto, S." "Legend of Zelda: Skies of Hyrule" 0003 002 "Molyneux, P." "Project Milo" 0004 002 "Molyneux, P." "Fable III" 0005 003 "Blow, J." "Ponytail" The structure of each line is basically proj_id, lec_id, lec_name, proj_name. Now, I'm currently reading the relevant data into the relevant objects. Thus, proj_id is stored in class Project whereas lec_name is a class Lecturer object, et al. The Lecturer and Project classes are not currently related. However, as I read in each line from the text file, for that line, I wish to read in the project offered by the lecturer into the Lecturer class; I'm already reading the proj_id into the Project class. I'd like to create an object in Lecturer called offered_proj which should be a set or list of the projects offered by that lecturer. Thus whenever, for a line, I read in a new project under the same lec_id, offered_proj will be updated with that project. If I wanted to get display a list of projects offered by a lecturer I'd ideally just want to use print lecturers[lec_id].offered_proj. My Python isn't great and I'd appreciate it if someone could show me a way to do that. I'm not sure if it's better as a set or a list, as well. Update After the advice from Alex Martelli and Oddthinking I went back and made some changes and tried to print the results. Here's the code snippet: for line in csv_file: proj_id = int(line[0]) lec_id = int(line[1]) lec_name = line[2] proj_name = line[3] projects[proj_id] = Project(proj_id, proj_name) lecturers[lec_id] = Lecturer(lec_id, lec_name) if lec_id in lecturers.keys(): lecturers[lec_id].offered_proj.add(proj_id) print lec_id, lecturers[lec_id].offered_proj The print lecturers[lec_id].offered_proj line prints the following output: 001 set([0001]) 001 set([0002]) 002 set([0003]) 002 set([0004]) 003 set([0005]) It basically feels like the set is being over-written or somesuch. So if I try to print for a specific lecturer print lec_id, lecturers[001].offered_proj all I get is the last the proj_id that has been read in.

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• nested function call faster or not ?

  - by KaluSingh Gabbar

  I have this silly argument with a friend and need a authoritative word on it. I have these two snippet and want to know which one is faster ? [A or B] (assuming that compiler does not optimize anything) [A] if ( foo () ); [B] int t = foo (); if ( t )

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• Qt vs .NET - a few comparisons [closed]

  - by Pirate for Profit

  Event Handling In Qt the event handling system you just emit signals when something cool happens and then catch them in slots, for instance emit valueChanged(int percent, bool something); and void MyCatcherObj::valueChanged(int p, bool ok){} blocking them and disconnecting them when needed, doing it across threads... once you get the hang of it, it just seems a lot more natural and intuitive than the way the .NET event handling is set up (you know, object sender, CustomEventArgs e). And I'm not just talking about syntax, because in the end the .NET delegate crap is the bomb. I'm also talking about in more than just reflection (because, yes, .NET obviously has much stronger reflection capabilities). I'm talking about in the way the system feels to a human being. Qt wins hands down i m o. Basically, the footprints make more sense and you can visualize the project easier without the clunky event handling system. I wish I could it explain it better. The only thing is, I do love some of the ease of C# compared to C++ and .NET's assembly architecture. That is a big bonus for modular projects, which are a PITA to do in C++. Database Ease of Doing Crap Also what about datasets and database manipulations. I think .net wins here but I'm not sure. Threading/Conccurency How do you guys think of the threading? In .NET, all I've ever done is make like a list of master worker threads with locks. I like QConcurrentFramework, you don't worry about locks or anything, and with the ease of the signal slot system across threads it's nice to get notified about the progress of things. Memory Usage Also what do you think of the overall memory usage comparison. Is the .NET garbage collector pretty on the ball and quick compared to the instantaneous nature of native memory management? Or does it just let programs leak up a storm and lag the computer then clean it up when it's about to really lag? However, I am a n00b who doesn't know what I'm talking about, please school me on the subject.

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• Can parser combination be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and shift oop f op (P(g, xs)) = let h, xs = loop (op, g, xs) loop (oop, f h, xs) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) | oop, f, ('^' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) | '^' -> pown loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '-'::P(f, xs) -> let f, xs = loop ('~', f, xs) P(-f, xs) | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• Segfault (possibly due to casting)

  - by BSchlinker

  I don't normally go to stackoverflow for sigsegv errors, but I have done all I can with my debugger at the moment. The segmentation fault error is thrown following the completion of the function. Any ideas what I'm overlooking? I suspect that it is due to the casting of the sockaddr to the sockaddr_in, but I am unable to find any mistakes there. (Removing that line gets rid of the seg fault -- but I know that may not be the root cause here). // basic setup int sockfd; char str[INET_ADDRSTRLEN]; sockaddr* sa; socklen_t* sl; struct addrinfo hints, *servinfo, *p; int rv; memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_DGRAM; // return string string foundIP; // setup the struct for a connection with selected IP if ((rv = getaddrinfo("4.2.2.1", NULL, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return "1"; } // loop through all the results and make a socket for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("talker: socket"); continue; } break; } if (p == NULL) { fprintf(stderr, "talker: failed to bind socket\n"); return "2"; } // connect the UDP socket to something connect(sockfd, p->ai_addr, p->ai_addrlen); // we need to connect to get the systems local IP // get information on the local IP from the socket we created getsockname(sockfd, sa, sl); // convert the sockaddr to a sockaddr_in via casting struct sockaddr_in *sa_ipv4 = (struct sockaddr_in *)sa; // get the IP from the sockaddr_in and print it inet_ntop(AF_INET, &(sa_ipv4->sin_addr), str, INET_ADDRSTRLEN); printf("%s\n", str); // return the IP return foundIP; }

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