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• Adding a valuetype to IDL, compile and it fails with "No factory found"

  - by jim

  I can't figure out why the client keeps complaining about the not finding the factory method. I've tried the IDL with and without the "factory" keyword and that didn't change the behavior. The SDMGeoVT IDL matches other objects used (which run successfully). The SDMGeoVT classes generated match other generated classes in regards to inheritance and methods. The IDL is as follows; The idlj compiler runs w/o error. I implement the function on the server and I see the server code run and serialize the object over the wire (the server code runs fine). The client bombs with the following stack trace (the first couple of lines is from the jacORB library). I've created a small app just to compile and test the code (ArrayClient & ArrayServer). The base app (from the jacORB demo) works fine. I've tried using the base class OFBaseVT and a single object (SDMGeoVT vs the list return) and have the same issue. 2010-05-27 15:37:11.813 FINE read GIOP message of size 100 from ClientGIOPConnection to 127.0.0.1:47030 (1e4853f) 2010-05-27 15:37:11.813 FINE read GIOP message of size 100 from ClientGIOPConnection to 127.0.0.1:47030 (1e4853f) org.omg.CORBA.MARSHAL: No factory found for: IDL:pl/SDMGeoVT:1.0 at org.jacorb.orb.CDRInputStream.read_untyped_value(CDRInputStream.java:2906) at org.jacorb.orb.CDRInputStream.read_typed_value(CDRInputStream.java:3082) at org.jacorb.orb.CDRInputStream.read_value(CDRInputStream.java:2679) at com.helloworld.pl.SDMGeoVTHelper.read(SDMGeoVTHelper.java:106) at com.helloworld.pl.SDMGeoVTListHelper.read(SDMGeoVTListHelper.java:51) at com.helloworld.pl._PLManagerIFStub.getSDMGeos(_PLManagerIFStub.java:28) at com.helloworld.ArrayClient.<init>(ArrayClient.java:40) at com.helloworld.ArrayClient.main(ArrayClient.java:125) valuetype SDMGeoVT : common::OFBaseVT{ private string sdmName; private string zip; private string atz; private long long primaryDeptId; private string deptName; factory instance(in string name,in string ZIP,in string ATZ,in long long primaryDeptId,in string deptName,in string name); string getZIP(); void setZIP(in string ZIP); string getATZ(); void setATZ(in string ATZ); long long getPrimaryDeptId(); void setPrimaryDeptId(in long long primaryDeptId); string getDeptName(); void setDeptName(in string deptName); }; typedef sequence<SDMGeoVT> SDMGeoVTList; interface PLManagerIF : PublicManagerIF { pl::SDMGeoVTList getSDMGeos(in framework::ITransactionHandle tHandle, in long long productionLocationId); };

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• Optimizing spacing of mesh containing a given set of points

  - by Feynman

  I tried to summarize the this as best as possible in the title. I am writing an initial value problem solver in the most general way possible. I start with an arbitrary number of initial values at arbitrary locations (inside a boundary.) The first part of my program creates a mesh/grid (I am not sure which is the correct nuance), with N points total, that contains all the initial values. My goal is to optimize the mesh such that the spacing is as uniform as possible. My solver seems to work half decently (it needs some more obscure debugging that is not relevant here.) I am starting with one dimension. I intend to generalize the algorithm to an arbitrary number of dimensions once I get it working consistently. I am writing my code in fortran, but feel free to reply with pseudocode or the language of your choice. Allow me to elaborate with an example: Say I am working on a closed interval [1,10] xmin=1 xmax=10 Say I have 3 initial points: xmin, 5 and xmax num_ivc=3 known(num_ivc)=[xmin,5,xmax] //my arrays start at 1. Assume "known" starts sorted I store my mesh/grid points in an array called coord. Say I want 10 points total in my mesh/grid. N=10 coord(10) Remember, all this is arbitrary--except the variable names of course. The algorithm should set coord to {1,2,3,4,5,6,7,8,9,10} Now for a less trivial example: num_ivc=3 known(num_ivc)=[xmin,5.5,xmax or just num_ivc=1 known(num_ivc)=[5.5] Now, would you have 5 evenly spaced points on the interval [1, 5.5] and 5 evenly spaced points on the interval (5.5, 10]? But there is more space between 1 and 5.5 than between 5.5 and 10. So would you have 6 points on [1, 5.5] followed by 4 on (5.5 to 10]. The key is to minimize the difference in spacing. I have been working on this for 2 days straight and I can assure you it is a lot trickier than it sounds. I have written code that only works if N is large only works if N is small only works if it the known points are close together only works if it the known points are far apart only works if at least one of the known points is near a boundary only works if none of the known points are near a boundary So as you can see, I have coded the gamut of almost-solutions. I cannot figure out a way to get it to perform equally well in all possible scenarios (that is, create the optimum spacing.)

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• Problem with return 2 libc method

  - by jth

  Hi, I'am trying to understand the return2libc method. I'am using an ubuntu linux 9.10, 32 bit with ASLR disabled. In theory, it sounds quite easy, overwrite the saved eip with the address of system() (or whatever function you want), then put the address to which system() should return and after that, the parameter for system, the "/bin/bash"-string. But what happens is that my exploit keeps segfaulting the vulnerable program. I assume something with the system()-address went wrong. This is what I did so far: Determined the address of system(): (gdb) print system $1 = {<text variable, no debug info>} 0x167020 <system> (gdb) x/x system 0x167020 <system>: 0x890cec83 I used the subsequent x/x system because those 3 bytes returned by print system looks like an index in some sort of jumptable (PLT?), so I assume 0x890cec83 is the right address which is used to overwrite the saved eip. After that I determined the address of the /bin/bash string in memory, using a small C program which basically consists of this line: printf("Address of string /bin/bash: %p\n", getenv("SHELL")); Then I looked a little bit around in the memory and fount /bin/bash: (gdb) x/s 0xbffff6ca 0xbffff6ca: "/bin/bash" After I gathered this information, I filled the buffer: (gdb) b 9 Breakpoint 1 at 0x8048407: file victim.c, line 9. (gdb) r `perl -e 'print "A"x9 . "\x83\xec\x0c\x89FAKE\xca\f6\ff\bf";'` Breakpoint 1, main (argc=1111638594, argv=0xc360cca) at victim.c:10 10 return 0; (gdb) x/s 0xbffff6ca 0xbffff6ca: "/bin/bash" Stack frame looks like this: (gdb) i f Stack level 0, frame at 0xbffff440: eip = 0x8048407 in main (victim.c:10); saved eip 0x890cec83 source language c. Arglist at 0xbffff438, args: argc=1111638594, argv=0xc360cca Locals at 0xbffff438, Previous frame's sp is 0xbffff440 Saved registers: ebp at 0xbffff438, eip at 0xbffff43c This seems all right to me, saved eip was overwritten with the (hopefully) correct system()-address, return address for system was set to "FAKE" (shouldn't matter) and the address of /bin/bash also seems to be correct. When I'am continuing the execution, victim segfaults on some strange address and certainly not in 0x890cec83: (gdb) cont Continuing. Program received signal SIGSEGV, Segmentation fault. 0x0804840d in main (argc=Cannot access memory at address 0x41414149 ) at victim.c:11 11 } Has anyone an explanation or a hint what happens here and why the execution isn't redirected to 0x890cec83? Thanks in advance, any hint, and be it only vague, would be appreciated. I have no idea why this doesn't work.

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• Logging in with WebFinger and OpenID

  - by Ryan

  I would like to apologize in advance for the ugly formatting. In order to talk about the problem, I need to be posting a bunch of URLs, but the excessive URLs and my lack of reputation makes StackOverflow think I could be a spammer. Any instance of 'ht~tp' is supposed to be 'http'. '{dot}' is supposed to be '.' and '{colon}' is supposed to be ':'. Also, my lack of reputation has prevented me from tagging my question with 'webfinger' and 'google-profiles'. Onto my question: I am messing around with WebFinger and trying to create a small rails app that enables a user to log in using nothing but their WebFinger account. I can succesfully finger myself, and I get back an XRD file with the following snippet: Link rel="ht~tp://specs{dot}openid{dot}net/auth/2.0/provider" href="ht~tp://www{dot}google{dot}com/profiles/{redacted}"/ Which, to me, reads, "I have an OpenID 2.0 login at the url: ht~tp://www{dot}google{dot}com/profiles/{redacted}". But when I try to use that URL to log in, I get the following error OpenID::DiscoveryFailure (Failed to fetch identity URL ht~tp://www{dot}google{dot}com/profiles/{redacted} : Error encountered in redirect from ht~tp://www{dot}google{dot}com/profiles/{redacted}: Error fetching /profiles/{Redacted}: Connection refused - connect(2)): When I replace the profile URL with 'ht~tps://www{dot}google{dot}com/accounts/o8/id', the login works perfectly. here is the code that I am using (I'm using RedFinger as a plugin, and JanRain's ruby-openid, installed without the gem) require "openid" require 'openid/store/filesystem.rb' class SessionsController < ApplicationController def new @session = Session.new #render a textbox requesting a webfinger address, and a submit button end def create ####################### # # Pay Attention to this section right here # ####################### #use given webfinger address to retrieve openid login finger = Redfinger.finger(params[:session][:webfinger_address]) openid_url = finger.open_id.first.to_s #openid_url is now: ht~tp://www{dot}google{dot}com/profiles/{redacted} #Get needed info about the acquired OpenID login file_store = OpenID::Store::Filesystem.new("./noncedir/") consumer = OpenID::Consumer.new(session,file_store) response = consumer.begin(openid_url) #ERROR HAPPENS HERE #send user to OpenID login for verification redirect_to response.redirect_url('ht~tp://localhost{colon}3000/','ht~tp://localhost{colon}3000/sessions/complete') end def complete #interpret return parameters file_store = OpenID::Store::Filesystem.new("./noncedir/") consumer = OpenID::Consumer.new(session,file_store) response = consumer.complete params case response.status when OpenID::SUCCESS session[:openid] = response.identity_url #redirect somehwere here end end end Is it possible for me to use the URL I received from my WebFinger to log in with OpenID?

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• Suggestions for designing large-scale Java webapp from the ground up

  - by Chris Thompson

  Hi all, I'm about to start developing a large-scale system and I'm struggling with which direction to proceed. I've done plenty of Java web apps before and I have plenty of experience with servlet containers and GWT and some experience with Spring. The problem is most of my webapps have been thrown together just to be a proof of concept and what I'm struggling with is what set of frameworks to use. I need to have both a browser based application as well as a web service designed to support access from mobile devices (Android and iPhone for now). Ideally, I'd like to design this system in such a way that I don't end up rewriting all of my servlets for each client (browser and phone) although I don't mind having some small checks in there to properly format the data. In addition, although I'm the only developer now, that won't necessarily be the case down the road and I'd like to design something that scales well both with regards to traffic and number of developers (isn't just a nightmare to maintain). So where I am now is planning on using GWT to design the browser-based interface but I'm struggling with how to reuse that code with to present the interface (most likely xml) for the mobile devices. Using GWT RPC would, I think, make it relatively easy to do all of the AJAX in the browser, but might make generating xml for the mobile phones difficult. In addition, I like the idea of using something like Hibernate for persistence and Spring Security to secure the whole thing. Again, I'm not sure how well those will cooperate with GWT (I think Hibernate should be fine...) There's obviously a lot more to this than I've presented here, but I've tried to give you the 5-minute overview. I'm a bit stumped and was wondering if anybody in the community had any experience starting from this place. Does what I'm trying to do make sense? Is it realistic? I have no doubt I can make all of these frameworks speak the same language, I'm just wondering if it's worth my time to fight with them. Also, am I missing a framework that would be really beneficial? Thanks in advance and sorry for the relatively broad question... Chris

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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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• php , SimpleXML, while loop

  - by Michael

  I'm trying to get some information from ebay api and store it in database . I used simple xml to extract the information but I have a small issue as the information is not displayed for some items . if I make a print to the simple_xml I can see very well that the information is provided by ebay api . I have $items = "220617293997,250645537939,230485306218,110537213815,180519294810"; $number_of_items = count(explode(",", $items)); $xml = $baseClass->getContent("http://open.api.ebay.com/shopping?callname=GetMultipleItems&responseencoding=XML&appid=Morcovar-c74b-47c0-954f-463afb69a4b3&siteid=0&version=525&IncludeSelector=ItemSpecifics&ItemID=$items"); writeDoc($xml, "api.xml"); //echo $xml; $getvalues = simplexml_load_file('api.xml'); // print_r($getvalue); $number = "0"; while($number < 6) { $item_number = $getvalues->Item[$number]->ItemID; $location = $getvalues->Item[$number]->Location; $title = $getvalues->Item[$number]->Title; $price = $getvalues->Item[$number]->ConvertedCurrentPrice; $manufacturer = $getvalues->Item[$number]->ItemSpecifics->NameValueList[3]->Value; $model = $getvalues->Item[$number]->ItemSpecifics->NameValueList[4]->Value; $mileage = $getvalues->Item[$number]->ItemSpecifics->NameValueList[5]->Value; echo "item number = $item_number <br>localtion = $location<br>". "title = $title<br>price = $price<br>manufacturer = $manufacturer". "<br>model = $model<br>mileage = $mileage<br>"; $number++; } the above code returns item number = localtion = title = price = manufacturer = model = mileage = item number = 230485306218 localtion = Coventry, Warwickshire title = 2001 LAND ROVER RANGE ROVER VOGUE AUTO GREEN price = 3635.07 manufacturer = Land Rover model = Range Rover mileage = 76000 item number = 220617293997 localtion = Crawley, West Sussex title = 2004 CITROEN C5 HDI LX RED price = 3115.77 manufacturer = Citroen model = C5 mileage = 76000 item number = 180519294810 localtion = London, London title = 2000 VOLKSWAGEN POLO 1.4 SILVER 16V NEED GEAR BOX price = 905.06 manufacturer = Right-hand drive model = mileage = Standard Car item number = localtion = title = price = manufacturer = model = mileage = As you can see the information is not retrieved for a few items ... If I replace the $number manually like " $item_number = $getvalues-Item[4]-ItemID;" works well for any number .

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• Mapping two tables 0..n in Hibernate

  - by simon

  I have a table Users CREATE TABLE "USERS" ( "ID" NUMBER NOT NULL , "LOGINNAME" VARCHAR2 (150) NOT NULL ) and I have a second table SpecialUsers. No UserId can occur twice in the SpecialUsers table, and only a small subset of the ids of users in the Users table are contained in the SpecialUsers table. CREATE TABLE "SPECIALUSERS" ( "USERID" NUMBER NOT NULL, CONSTRAINT "PK_SPECIALUSERS" PRIMARY KEY ("USERID") ) ALTER TABLE "SPECIALUSERS" ADD CONSTRAINT "FK_SPECIALUSERS_USERID" FOREIGN KEY ("USERID") REFERENCES "USERS" ("ID") / Mapping the Users table in Hibernate works ok <hibernate-mapping package="com.initech.domain"> <class name="com.initech.User" table="USERS"> <id name="id" column="ID" type="java.lang.Long"> <meta attribute="use-in-tostring">true</meta> <generator class="sequence"> <param name="sequence">SEQ_USERS_ID</param> </generator> </id> <property name="loginName" column="LOGINNAME" type="java.lang.String" not-null="true"> <meta attribute="use-in-tostring">true</meta> </property> </class> </hibernate-mapping> But I'm struggling in creating the mapping for the SpecialUsers table. All the examples (e.g. in Hibernate documentation) in Internet I found don't have this type of self-reference. I tried a mapping like this: <hibernate-mapping package="com.initech.domain"> <class name="com.initech.User" table="SPECIALUSERS"> <id name="id" column="USERID"> <meta attribute="use-in-tostring">true</meta> <generator class="foreign"> <param name="property">user</param> </generator> </id> <one-to-one name="user" class="User"/> </class> </hibernate-mapping> but got the error Invocation of init method failed; nested exception is org.hibernate.DuplicateMappingException: Duplicate class/entity mapping com.initech.User How should I map the SpecialUsers table? What I need on the application level is a list of the User objects contained in the SpecialUsers table.

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• Reliable and fast way to convert a zillion ODT files in PDF?

  - by Marco Mariani

  I need to pre-produce a million or two PDF files from a simple template (a few pages and tables) with embedded fonts. Usually, I would stay low level in a case like this, and compose everything with a library like ReportLab, but I joined late in the project. Currently, I have a template.odt and use markers in the content.xml files to fill with data from a DB. I can smoothly create the ODT files, they always look rigth. For the ODT to PDF conversion, I'm using openoffice in server mode (and PyODConverter w/ named pipe), but it's not very reliable: in a batch of documents, there is eventually a point after which all the processed files are converted into garbage (wrong fonts and letters sprawled all over the page). Problem is not predictably reproducible (does not depend on the data), happens in OOo 2.3 and 3.2, in Ubuntu, XP, Server 2003 and Windows 7. My Heisenbug detector is ticking. I tried to reduce the size of batches and restarting OOo after each one; still, a small percentage of the documents are messed up. Of course I'll write about this on the Ooo mailing lists, but in the meanwhile, I have a delivery and lost too much time already. Where do I go? Completely avoid the ODT format and go for another template system. Suggestions? Anything that takes a few seconds to run is way too slow. OOo takes around a second and it sums to 15 days of processing time. I had to write a program for clustering the jobs over several clients. Keep the format but go for another tool/program for the conversion. Which one? There are many apps in the shareware or commercial repositories for windows, but trying each one is a daunting task. Some are too slow, some cannot be run in batch without buying it first, some cannot work from command line, etc. Open source tools tend not to reinvent the wheel and often depend on openoffice. Converting to an intermediate .DOC format could help to avoid the OOo bug, but it would double the processing time and complicate a task that is already too hairy. Try to produce the PDFs twice and compare them, discarding the whole batch if there's something wrong. Although the documents look equal, I know of no way to compare the binary content. Restart OOo after processing each document. it would take a lot more time to produce them it would lower the percentage of the wrong files, and make it very hard to identify them. Go for ReportLab and recreate the pages programmatically. This is the approach I'm going to try in a few minutes. Learn to properly format bulleted lists Thanks a lot.

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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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• Webserver parsing chrome input from post request

  - by ravenspoint

  I am developing a small embedded web server. I want to add parsing of post requests, but I am having a problem with input password fields from Chrome. Firefox and IE work perfectly. The HTML: <form action=start.webem method=post> <input value="START" type=submit /><!--#webem start --> <p>Password: <input TYPE=PASSWORD name=yourname AUTOCOMPLETE=OFF /><br> </form> From Firefox I get POST /stop.webem HTTP/1.1 Host: 127.0.0.1:8080 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.9) Gecko/20100315 Firefox/3.5.9 (.NET CLR 3.5.30729) Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 300 Connection: keep-alive Referer: http://127.0.0.1:8080/ Content-Type: application/x-www-form-urlencoded Content-Length: 13 yourname=test However from Chrome, about 90% of the time, the yourname=test is missing POST /start.webem HTTP/1.1 Host: 127.0.0.1:8080 Connection: keep-alive User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1045 Safari/532.5 Referer: http://127.0.0.1:8080/ Content-Length: 13 Cache-Control: max-age=0 Origin: http://127.0.0.1:8080 Content-Type: application/x-www-form-urlencoded Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 Though, occasionally it does work!!! POST /start.webem HTTP/1.1 Host: 127.0.0.1:8080 Connection: keep-alive User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1045 Safari/532.5 Referer: http://127.0.0.1:8080/start.webem Content-Length: 13 Cache-Control: max-age=0 Origin: http://127.0.0.1:8080 Content-Type: application/x-www-form-urlencoded Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 yourname=test I cannot find what causes it to work sometimes.

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• Artichow PlotGroup: Legends not showing

  - by Hameed

  I am working on a little project on OpenCATS, developing some charts. In one of the charts, I need to add multiple plots to a PlotGroup and add Legends as well. I have written a small function that creates the chart, however I have difficulty displaying the legends when I add them to a PlotGroup object. Here is the code: public function draw($format = false) { /* Make sure we have GD support. */ if (!function_exists('imagecreatefromjpeg')) { die(); } if ($format === false) { $format = IMG_PNG; } $group = new PlotGroup(); $graph = new Graph($this->width, $this->height, NULL, 0, $this->width-135); $graph->setFormat($format); $graph->setBackgroundColor(new Color(0xF4, 0xF4, 0xF4)); $graph->shadow->setSize(3); $graph->title->set($this->title); $graph->title->setFont(new Tuffy(10)); $graph->title->setColor(new Color(0x00, 0x00, 0x8B)); $graph->border->setColor(new Color(187, 187, 187, 15)); $group->axis->bottom->setLabelText($this->xLabels); $group->axis->bottom->label->setFont(new Tuffy(8)); $group->setPadding(25, 145, 10, 22); $plotcount = 0; $plot = array(); foreach ($this->xValues as $xVal) { $plotcount++; $plot[$plotcount-1] = new LinePlot($xVal, LinePlot::LINE); $plot[$plotcount-1]->setPadding(25, 145, 10, 22); if ($plotcount % 5 ==0 ) $plot[$plotcount-1]->setColor(new Blue); else if ($plotcount % 4 ==0 ) $plot[$plotcount-1]->setColor(new DarkGreen); else if ($plotcount % 3 ==0 ) $plot[$plotcount-1]->setColor(new Red); else if ($plotcount % 2 ==0 ) $plot[$plotcount-1]->setColor(new Orange); $plot[$plotcount-1]->setThickness(2); $plot[$plotcount-1]->legend->add($plot[$plotcount-1], $this->legends[$plotcount-1]); $plot[$plotcount-1]->legend->setTextFont(new Tuffy(8)); $plot[$plotcount-1]->legend->setPadding(3, 3, 3, 3, 3); $plot[$plotcount-1]->legend->setPosition(1, 0.825); $plot[$plotcount-1]->legend->setBackgroundColor(new Color(0xFF, 0xFF, 0xFF)); $plot[$plotcount-1]->legend->border->setColor(new Color(0xD0, 0xD0, 0xD0)); $plot[$plotcount-1]->legend->shadow->setSize(0); $group->add($plot[$plotcount-1]); } $graph->add($group); $graph->draw(); } } If I draw only one LinePlot it works: So for instance if I change $graph->add($group); to $graph->add($plot[0]); then only one of the lines will show up with the legend next to it.

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• Exception in thread "main" java.lang.StackOverflowError

  - by Ray.R.Chua

  I have a piece of code and I could not figure out why it is giving me Exception in thread "main" java.lang.StackOverflowError. This is the question: Given a positive integer n, prints out the sum of the lengths of the Syracuse sequence starting in the range of 1 to n inclusive. So, for example, the call: lengths(3) will return the the combined length of the sequences: 1 2 1 3 10 5 16 8 4 2 1 which is the value: 11. lengths must throw an IllegalArgumentException if its input value is less than one. My Code: import java.util.HashMap; public class Test { HashMap<Integer,Integer> syraSumHashTable = new HashMap<Integer,Integer>(); public Test(){ } public int lengths(int n)throws IllegalArgumentException{ int sum =0; if(n < 1){ throw new IllegalArgumentException("Error!! Invalid Input!"); } else{ for(int i =1; i<=n;i++){ if(syraSumHashTable.get(i)==null) { syraSumHashTable.put(i, printSyra(i,1)); sum += (Integer)syraSumHashTable.get(i); } else{ sum += (Integer)syraSumHashTable.get(i); } } return sum; } } private int printSyra(int num, int count){ int n = num; if(n == 1){ return count; } else{ if(n%2==0){ return printSyra(n/2, ++count); } else{ return printSyra((n*3)+1, ++count) ; } } } } Driver code: public static void main(String[] args) { // TODO Auto-generated method stub Test s1 = new Test(); System.out.println(s1.lengths(90090249)); //System.out.println(s1.lengths(5)); } . I know the problem lies with the recursion. The error does not occur if the input is a small value, example: 5. But when the number is huge, like 90090249, I got the Exception in thread "main" java.lang.StackOverflowError. Thanks all for your help. :) I almost forgot the error msg: Exception in thread "main" java.lang.StackOverflowError at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:65) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60) at Test.printSyra(Test.java:60)

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• Recursive N-way merge/diff algorithm for directory trees?

  - by BobMcGee

  What algorithms or Java libraries are available to do N-way, recursive diff/merge of directories? I need to be able to generate a list of folder trees that have many identical files, and have subdirectories with many similar files. I want to be able to use 2-way merge operations to quickly remove as much redundancy as possible. Goals: Find pairs of directories that have many similar files between them. Generate short list of directory pairs that can be synchronized with 2-way merge to eliminate duplicates Should operate recursively (there may be nested duplicates of higher-level directories) Run time and storage should be O(n log n) in numbers of directories and files Should be able to use an embedded DB or page to disk for processing more files than fit in memory (100,000+). Optional: generate an ancestry and change-set between folders Optional: sort the merge operations by how many duplicates they can elliminate I know how to use hashes to find duplicate files in roughly O(n) space, but I'm at a loss for how to go from this to finding partially overlapping sets between folders and their children. EDIT: some clarification The tricky part is the difference between "exact same" contents (otherwise hashing file hashes would work) and "similar" (which will not). Basically, I want to feed this algorithm at a set of directories and have it return a set of 2-way merge operations I can perform in order to reduce duplicates as much as possible with as few conflicts possible. It's effectively constructing an ancestry tree showing which folders are derived from each other. The end goal is to let me incorporate a bunch of different folders into one common tree. For example, I may have a folder holding programming projects, and then copy some of its contents to another computer to work on it. Then I might back up and intermediate version to flash drive. Except I may have 8 or 10 different versions, with slightly different organizational structures or folder names. I need to be able to merge them one step at a time, so I can chose how to incorporate changes at each step of the way. This is actually more or less what I intend to do with my utility (bring together a bunch of scattered backups from different points in time). I figure if I can do it right I may as well release it as a small open source util. I think the same tricks might be useful for comparing XML trees though.

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• How to make freelance clients understand the costs of developing and maintaining mature products?

  - by John

  I have a freelance web application project where the client requests new features every two weeks or so. I am unable to anticipate the requirements of upcoming features. So when the client requests a new feature, one of several things may happen: I implement the feature with ease because it is compatible with the existing platform I implement the feature with difficulty because I have to rewrite a significant portion of the platform's foundation Client withdraws request because it costs too much to implement against existing platform At the beginning of the project, for about six months, all feature requests fell under category 1) because the system was small and agile. But for the past six months, most feature implementation fell under category 2). The system is mature, forcing me to refactor and test everytime I want to add new modules. Additionally, I find myself breaking things that use to work, and fixing it (I don't get paid for this). The client is starting to express frustration at the time and cost for me to implement new features. To them, many of the feature requests are of the same scale as the features they requested six months ago. For example, a client would ask, "If it took you 1 week to build a ticketing system last year, why does it take you 1 month to build an event registration system today? An event registration system is much simpler than a ticketing system. It should only take you 1 week!" Because of this scenario, I fear feature requests will soon land in category 3). In fact, I'm already eating a lot of the cost myself because I volunteer many hours to support the project. The client is often shocked when I tell him honestly the time it takes to do something. The client always compares my estimates against the early months of a project. I don't think they're prepared for what it really costs to develop, maintain and support a mature web application. When working on a salary for a full time company, managers were more receptive of my estimates and even encouraged me to pad my numbers to prepare for the unexpected. Is there a way to condition my clients to think the same way? Can anyone offer advice on how I can continue to work on this web project without eating too much of the cost myself? Additional info - I've only been freelancing full time for 1 year. I don't yet have the high end clients, but I'm slowly getting there. I'm getting better quality clients as time goes by.

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• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

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• What is the Fastest Way to Check for a Keyword in a List of Keywords in Delphi?

  - by lkessler

  I have a small list of keywords. What I'd really like to do is akin to: case MyKeyword of 'CHIL': (code for CHIL); 'HUSB': (code for HUSB); 'WIFE': (code for WIFE); 'SEX': (code for SEX); else (code for everything else); end; Unfortunately the CASE statement can't be used like that for strings. I could use the straight IF THEN ELSE IF construct, e.g.: if MyKeyword = 'CHIL' then (code for CHIL) else if MyKeyword = 'HUSB' then (code for HUSB) else if MyKeyword = 'WIFE' then (code for WIFE) else if MyKeyword = 'SEX' then (code for SEX) else (code for everything else); but I've heard this is relatively inefficient. What I had been doing instead is: P := pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX '); case P of 1: (code for CHIL); 6: (code for HUSB); 11: (code for WIFE); 17: (code for SEX); else (code for everything else); end; This, of course is not the best programming style, but it works fine for me and up to now didn't make a difference. So what is the best way to rewrite this in Delphi so that it is both simple, understandable but also fast? (For reference, I am using Delphi 2009 with Unicode strings.) Followup: Toby recommended I simply use the If Then Else construct. Looking back at my examples that used a CASE statement, I can see how that is a viable answer. Unfortunately, my inclusion of the CASE inadvertently hid my real question. I actually don't care which keyword it is. That is just a bonus if the particular method can identify it like the POS method can. What I need is to know whether or not the keyword is in the set of keywords. So really I want to know if there is anything better than: if pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX ') > 0 then The If Then Else equivalent does not seem better in this case being: if (MyKeyword = 'CHIL') or (MyKeyword = 'HUSB') or (MyKeyword = 'WIFE') or (MyKeyword = 'SEX') then In Barry's comment to Kornel's question, he mentions the TDictionary Generic. I've not yet picked up on the new Generic collections and it looks like I should delve into them. My question here would be whether they are built for efficiency and how would using TDictionary compare in looks and in speed to the above two lines? In later profiling, I have found that the concatenation of strings as in: (' ' + MyKeyword + ' ') is VERY expensive time-wise and should be avoided whenever possible. Almost any other solution is better than doing this.

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• Visual Studio soft-crashing when encountering XAML Errors in initialize.

  - by Aren

  I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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• Linking buttion to jQuery through service

  - by Ruddy

  I have a small problem that should be very easy to overcome. For some reason I cant work this out. So the problem is I cannot get a button to link to some jquery. My set-up is as follows (showing the relevant code): Default.aspx jQuery: function getContent() { var data = { numberID: 1 }; $.jsonAspNet("ContentService.asmx", "GetContent", data, function (result) { $('#content').html(result); }); } jQuery(document).ready(function () { getContent(); } HTML: <div id="content"></div> ContentService.vb Public Function GetContent(number As Integer) As String Dim sb = New StringBuilder sb.AppendLine("<table>") sb.AppendLine("<tr>") sb.AppendLine("<td class='ui-widget-header ui-corner-all'>Number</td>") sb.AppendLine("</tr>") sb.AppendLine("<tr>") sb.AppendLine("<td>" & number & "</td>") sb.AppendLine("<td><a href='#' id='test' class='fg-button ui-state-default ui-corner-all'><img src='" & Context.Request.ApplicationPath & "/images/spacer.gif' class='ui-icon ui-icon-pencil' /></a></td>") sb.AppendLine("</tr>") sb.AppendLine("</table>") Return sb.ToString End Function So that's the basics of what I have everything works but I'm not sure how to get the button (id='test') to get linked to some jQuery. I want it to be pressed and bring up a popup. I have tried to put the jQuery on default.aspx but this doesn't seem to work unless the button is place in the HTML on that page. $('#test').unbind('click').click(function () { alert('Working'); }); I'm sure this is easy to be able to do but I have been trying for a while and cannot seem to get it to work.

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• HowTo stick QDialog to Screen Borders like Skype do?

  - by mosg

  Hello. A long time ago I tried to find method how to stick QDialog window to screen borders for my small projects like Skype windows do it, but I failed. May be I was looking this code not in the right place, so now I'm looking the solution here, on stack! :) So, does any one have a deal with some kind of such code, links, samples? In my opinion, we have to reimplement QDialog moveEvent function, like below, but that code does not working: void CDialog::moveEvent(QMoveEvent * event) { QRect wndRect; int leftTaskbar = 0, rightTaskbar = 0, topTaskbar = 0, bottomTaskbar = 0; // int top = 0, left = 0, right = 0, bottom = 0; wndRect = this->frameGeometry(); // Screen resolution int screenWidth = QApplication::desktop()->width(); int screenHeight = QApplication::desktop()->height(); int wndWidth = wndRect.right() - wndRect.left(); int wndHeight = wndRect.bottom() - wndRect.top(); int posX = event->pos().x(); int posY = event->pos().y(); // Snap to screen border // Left border if (posX >= -m_nXOffset + leftTaskbar && posX <= leftTaskbar + m_nXOffset) { //left = leftTaskbar; this->move(leftTaskbar, posY); return; } // Top border if (posY >= -m_nYOffset && posY <= topTaskbar + m_nYOffset) { //top = topTaskbar; this->move(posX, topTaskbar); return; } // Right border if (posX + wndWidth <= screenWidth - rightTaskbar + m_nXOffset && posX + wndWidth >= screenWidth - rightTaskbar - m_nXOffset) { //right = screenWidth - rightTaskbar - wndWidth; this->move(screenWidth - rightTaskbar - wndWidth, posY); return; } // Bottom border if (posY + wndHeight <= screenHeight - bottomTaskbar + m_nYOffset && posY + wndHeight >= screenHeight - bottomTaskbar - m_nYOffset) { //bottom = screenHeight - bottomTaskbar - wndHeight; this->move(posX, screenHeight - bottomTaskbar - wndHeight); return; } QDialog::moveEvent(event); } Thanks.

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• working on lists in python

  - by owca

  I'm trying to make a small modification to django lfs project, that will allow me to deactivate products with no stocks. Unfortunatelly I'm just beginning to learn python, so I have big trouble with its syntax. That's what I'm trying to do. I'm using method 'has_variants' which returns true if product has any. Then I'm building a list from variants for this product. Next for every product in this list (I've called it 'set') I check it's stock and set bool variable 'inactive' to true if product has no stocks and to false if there are any. Finally if 'inactive' is false I'm setting self.active to 0. Code fails in line with: set[] = s How to correct it ? def deactivate(self): """If there are no stocks, deactivate the product. Used in last step of checkout. """ if self.has_variants(): for s in self.variants.filter(active=True): set[] = s for var in set: if var.get_stock_amount() == 0: inactive = True else: inactive = False else: if self.get_stock_amount() == 0: inactive = True if inactive: self.active = False return 0 error log : Traceback (most recent call last): File "manage.py", line 11, in <module> execute_manager(settings) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/__i nit__.py", line 362, in execute_manager utility.execute() File "/home/purplecow/rails/purpledev/site-packages/django/core/management/__i nit__.py", line 303, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/bas e.py", line 195, in run_from_argv self.execute(*args, **options.__dict__) File "/home/purplecow/rails/purpledev/site-packages/django/core/management/bas e.py", line 213, in execute translation.activate('en-us') File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/_ _init__.py", line 73, in activate return real_activate(language) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/_ _init__.py", line 43, in delayed_loader return g['real_%s' % caller](*args, **kwargs) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 205, in activate _active[currentThread()] = translation(language) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 194, in translation default_translation = _fetch(settings.LANGUAGE_CODE) File "/home/purplecow/rails/purpledev/site-packages/django/utils/translation/t rans_real.py", line 180, in _fetch app = import_module(appname) File "/home/purplecow/rails/purpledev/site-packages/django/utils/importlib.py" , line 35, in import_module __import__(name) File "/home/purplecow/rails/purpledev/lfs/caching/__init__.py", line 1, in <mo dule> from listeners import * File "/home/purplecow/rails/purpledev/lfs/caching/listeners.py", line 10, in < module> from lfs.cart.models import Cart File "/home/purplecow/rails/purpledev/lfs/cart/models.py", line 8, in <module> from lfs.catalog.models import Product File "/home/purplecow/rails/purpledev/lfs/catalog/__init__.py", line 1, in <mo dule> from listeners import * File "/home/purplecow/rails/purpledev/lfs/catalog/listeners.py", line 5, in <m odule> from lfs.catalog.models import PropertyGroup File "/home/purplecow/rails/purpledev/lfs/catalog/models.py", line 589 set[] = s ^ SyntaxError: invalid syntax

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• Undesired "flashing" in Jquery dropdown menu?

  - by Tom

  Hi, I've got the following piece of Jquery: $("#collapse-menu > li > a").click(function() { $(this).toggleClass("expanded").toggleClass("collapsed").find("+ ul").slideToggle("medium"); }); What it basically does is expands or collapses a menu of nested "lists" which contain dropdowns (simplified example): <ul id="collapse-menu"> <li><a class="expanded">Basic Details</a> <ul> <li> <select> .... </select> </li> <li> <select> .... </select> </li> The code works absolutely fine EXCEPT when a large value is selected in any of the dropdowns. At that point, when clicked, the menu will still expand/collapse correctly but "flash" quickly while doing so, as if the entire element was being reset somehow. The data itself is fine but it's the flashing that's unwanted. The strange thing is that if a small value is selected in a dropdown, there's no flashing. When a large value is selected (say, above 30 in an age dropdown of 18-99), the flashing starts happening. Can anyone tell me why this is happening? Or whether there's something not right about the Jquery that's causing this. Thanks. UPDATE: Adding a bounty to this. Have tried a few similar plugins/solutions out there on the net but they all seem to suffer from this "flashing" problem when large dropdown values are selected by default. If it helps, here's a typical similar solution: http://www.i-marco.nl/weblog/jquery-accordion-menu/index_collapsed.html# ... but it suffers from the same problem when dropdowns are added inside the accordion. I hope someone has a clean solution, instead of needing to hack this somehow.

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• C++ type-checking at compile-time

  - by Masterofpsi

  Hi, all. I'm pretty new to C++, and I'm writing a small library (mostly for my own projects) in C++. In the process of designing a type hierarchy, I've run into the problem of defining the assignment operator. I've taken the basic approach that was eventually reached in this article, which is that for every class MyClass in a hierarchy derived from a class Base you define two assignment operators like so: class MyClass: public Base { public: MyClass& operator =(MyClass const& rhs); virtual MyClass& operator =(Base const& rhs); }; // automatically gets defined, so we make it call the virtual function below MyClass& MyClass::operator =(MyClass const& rhs); { return (*this = static_cast<Base const&>(rhs)); } MyClass& MyClass::operator =(Base const& rhs); { assert(typeid(rhs) == typeid(*this)); // assigning to different types is a logical error MyClass const& casted_rhs = dynamic_cast<MyClass const&>(rhs); try { // allocate new variables Base::operator =(rhs); } catch(...) { // delete the allocated variables throw; } // assign to member variables } The part I'm concerned with is the assertion for type equality. Since I'm writing a library, where assertions will presumably be compiled out of the final result, this has led me to go with a scheme that looks more like this: class MyClass: public Base { public: operator =(MyClass const& rhs); // etc virtual inline MyClass& operator =(Base const& rhs) { assert(typeid(rhs) == typeid(*this)); return this->set(static_cast<Base const&>(rhs)); } private: MyClass& set(Base const& rhs); // same basic thing }; But I've been wondering if I could check the types at compile-time. I looked into Boost.TypeTraits, and I came close by doing BOOST_MPL_ASSERT((boost::is_same<BOOST_TYPEOF(*this), BOOST_TYPEOF(rhs)>));, but since rhs is declared as a reference to the parent class and not the derived class, it choked. Now that I think about it, my reasoning seems silly -- I was hoping that since the function was inline, it would be able to check the actual parameters themselves, but of course the preprocessor always gets run before the compiler. But I was wondering if anyone knew of any other way I could enforce this kind of check at compile-time.

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• Write Scheme data structures so they can be eval-d back in, or alternative

  - by Jesse Millikan

  I'm writing an application (A juggling pattern animator) in PLT Scheme that accepts Scheme expressions as values for some fields. I'm attempting to write a small text editor that will let me "explode" expressions into expressions that can still be eval'd but contain the data as literals for manual tweaking. For example, (4hss->sexp "747") is a function call that generates a legitimate pattern. If I eval and print that, it becomes (((7 3) - - -) (- - (4 2) -) (- (7 2) - -) (- - - (7 1)) ((4 0) - - -) (- - (7 0) -) (- (7 2) - -) (- - - (4 3)) ((7 3) - - -) (- - (7 0) -) (- (4 1) - -) (- - - (7 1))) which can be "read" as a string, but will not "eval" the same as the function. For this statement, of course, what I need would be as simple as (quote (((7 3... but other examples are non-trivial. This one, for example, contains structs which print as vectors: pair-of-jugglers ; --> (#(struct:hand #(struct:position -0.35 2.0 1.0) #(struct:position -0.6 2.05 1.1) 1.832595714594046) #(struct:hand #(struct:position 0.35 2.0 1.0) #(struct:position 0.6 2.0500000000000003 1.1) 1.308996938995747) #(struct:hand #(struct:position 0.35 -2.0 1.0) #(struct:position 0.6 -2.05 1.1) -1.3089969389957472) #(struct:hand #(struct:position -0.35 -2.0 1.0) #(struct:position -0.6 -2.05 1.1) -1.8325957145940461)) I've thought of at least three possible solutions, none of which I like very much. Solution A is to write a recursive eval-able output function myself for a reasonably large subset of the values that I might be using. There (probably...) won't be any circular references by the nature of the data structures used, so that wouldn't be such a long job. The output would end up looking like `(((3 0) (... ; ex 1 `(,(make-hand (make-position ... ; ex 2 Or even worse if I could't figure out how to do it properly with quasiquoting. Solution B would be to write out everything as (read (open-input-string "(big-long-s-expression)")) which, technically, solves the problem I'm bringing up but is... ugly. Solution C might be a different approach of giving up eval and using only read for parsing input, or an uglier approach where the s-expression is used as directly data if eval fails, but those both seem unpleasant compared to using scheme values directly. Undiscovered Solution D would be a PLT Scheme option, function or library I haven't located that would match Solution A. Help me out before I start having bad recursion dreams again.

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• Advice on software / database design to avoid using cursors when updating database

  - by Remnant

  I have a database that logs when an employee has attended a course and when they are next due to attend the course (courses tend to be annual). As an example, the following employee attended course '1' on 1st Jan 2010 and, as the course is annual, is due to attend next on the 1st Jan 2011. As today is 20th May 2010 the course status reads as 'Complete' i.e. they have done the course and do not need to do it again until next year: EmployeeID CourseID AttendanceDate DueDate Status 123456 1 01/01/2010 01/01/2011 Complete In terms of the DueDate I calculate this in SQL when I update the employee's record e.g. DueDate = AttendanceDate + CourseFrequency (I pull course frequency this from a separate table). In my web based app (asp.net mvc) I pull back this data for all employees and display it in a grid like format for HR managers to review. This allows HR to work out who needs to go on courses. The issue I have is as follows. Taking the example above, suppose today is 2nd Jan 2011. In this case, employee 123456 is now overdue for the course and I would like to set the Status to Incomplete so that the HR manager can see that they need to action this i.e. get employee on the course. I could build a trigger in the database to run overnight to update the Status field for all employees based on the current date. From what I have read I would need to use cursors to loop over each row to amend the status and this is considered bad practice / inefficient or at least something to avoid if you can??? Alternatively, I could compute the Status in my C# code after I have pulled back the data from the database and before I display it on screen. The issue with this is that the Status in the database would not necessarily match what is shown on screen which just feels plain wrong to me. Does anybody have any advice on the best practice approach to such an issue? It helps, if I did use a cursor I doubt I would be looping over more than 1000 records at any given time. Maybe this is such small volume that using cursors is okay?

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