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• Real time location tracking - windows program or browser based?

  - by mawg

  I want to track a few hundred, maybe a few thousand people in real time. Let's say that the hardware aspects are sorted out and I can get the data into a database. Now, I want to get it out and show it, in real-time. Weeeell ... "real-enough" time. Let's say that I want to draw a floorplan of a building and plot everyone every 1 to 5 seconds. (I might want to show only certain "kinds" of people at the click of a button; I will need datamining, etc, but let's stick with the worse case scenario). I am comfortable enough with PHP, though not this sort of thing. I personally would be happier with a windows app coded in Delphi, but the trend seems to be to make everything browser based. So, the question, I guess is whether a browser can handle this and whether there are compelling arguments for a windows-based or browser-based solution. If browser-based can handle this (displaying a few thousand data-points a second), and there are no overwhelming arguments for windows then I guess I will go for browser-based and learn a few new tricks. The obvious advantage being that I could also re-use a large part of my code for (vehicle) tracking on Google maps.

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• nhibernate mapping: delete collection, insert new collection with old IDs

  - by npeBeg

  my issue lokks similar to this one: (link) but i have one-to-many association: <set name="Fields" cascade="all-delete-orphan" lazy="false" inverse="true"> <key column="[TEMPLATE_ID]"></key> <one-to-many class="MyNamespace.Field, MyLibrary"/> </set> (i also tried to use ) this mapping is for Template object. this one and the Field object has their ID generators set to identity. so when i call session.Update for the Template object it works fine, well, almost: if the Field object has an Id number, UPDATE sql request is called, if the Id is 0, the INSERT is performed. But if i delete a Field object from the collection it has no effect for the Database. I found that if i also call session.Delete for this Field object, everything will be ok, but due to client-server architecture i don't know what to delete. so i decided to delete all the collection elements from the DB and call session.Update with a new collection. and i've got an issue: nhibernate performs the UPDATE operation for the Field objects that has non-zero Id, but they are removed from DB! maybe i should use some other Id generator or smth.. what is the best way to make nhibernate perform "delete all"/"insert all" routine for the collection?

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• How to lazy process an xml documentwith hexpat?

  - by Florian

  In my search for a haskell library that can process large (300-1000mb) xml files i came across hexpat. There is an example in the Haskell Wiki that claims to -- Process document before handling error, so we get lazy processing. For testing purposes i have redirected the output to /dev/null and throw a 300mb file at it. Memory consumption kept rising until i had to kill the process. Now i removed the error handling from the process function: process :: String -> IO () process filename = do inputText <- L.readFile filename let (xml, mErr) = parse defaultParseOptions inputText :: (UNode String, Maybe XMLParseError) hFile <- openFile "/dev/null" WriteMode L.hPutStr hFile $ format xml hClose hFile return () As a result the function now uses constant memory. Why does the error handling result in massive memory consumption? As far as i understand xml and mErr are two seperate unevaluated thunks after the call to parse. Does format xml evaluate xml and build the evaluation tree of 'mErr'? If yes is there a way to handle the error while using constant memory? http://www.haskell.org/haskellwiki/Hexpat/

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• App crashes every second time a tableview row is selected in navigation controller setup

  - by Thaurin

  Disclaimer first: I'm pretty new to Objective-C and the retain model. I've been developing in a garbage collected .NET environment for the last five years, so I've been spoiled. I'm still learning. I'm having my iPhone app crash with EXC_BAD_ACCESS. It happens in a navigtation controller/tableview setup. When I select a row the first time, no problems. It switches in the child controller without problems. I go back and select the same row again. Program then proceeds to crash. Every other row works fine, but every second time a row is accessed, it's a crash. I've pinpointed the location where this happens. The child controller (which is a class that I reuse for every row of the same type) that's being switched into has an array of NSString's representing the rows that will be displayed. I set it before pushing the child viewcontroller. It's there where this apparently happens. I'm having a hard time debugging this problem, still wrestling with xcode and all. I fear there may be some vital information missing here, but maybe there is something you recognize here.

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• Javascript XMLHttpRequest Post method

  - by user535617

  Hey So I have a question about posting using an XMLHttpRequest. In theory, if I am to post a username and password to an https domain (which I have yet to get working, unfortunately) would the responseText then change to the next website, or should the text fields become filled in? What normally happens is you navigate to this page via browser, enter a username and password, and it uses a POST method when the submit button is clicked, doing some authentication under the hood and returning a different page. I feel like maybe the responseText should even stay exactly the same (which is what happens now), but I don't know as I have no experience with this kind of thing. this.requests[1].open("POST", "https://" + this.address, true); var query = "target=%2Fcgi-bin%2FStatusConfig.cgi%3FPage%3Dindex&userfile=&username=user&password=pass&log+in=Log+in"; this.requests[1].setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); this.requests[1].setRequestHeader("Content-length", query.length); this.requests[1].setRequestHeader("Keep-Alive", 115); this.requests[1].setRequestHeader("Connection", "keep-alive"); this.requests[1].setRequestHeader("Host", this.address); this.requests[1].send(query); this.requests[1].onreadystatechange = onReadyStateChange1; Then basically onReadyStateChange1 displays the responseText when ready. Any light that could be shed on what SHOULD be happening with the post and responseText would be very appreciated. As would any advice in getting the new, logged into page. For further clarification, what I'm trying to do is log in and then return the new page, because the login page displays only log in information/functionality and the page after logging in has a lot of relevant information. I'm not trying to check the credentials as much as I'm trying to get it (the script) to log in so it can access the next page. Granted, the credentials will have to be valid for that. Thanks all.

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• "no inclosing instance error " while getting top term frequencies for document from Lucene index

  - by Julia

  Hello ! I am trying to get the most occurring term frequencies for every particular document in Lucene index. I am trying to set the treshold of top occuring terms that I care about, maybe 20 However, I am getting the "no inclosing instance of type DisplayTermVectors is accessible" when calling Comparator... So to this function I pass vector of every document and max top terms i would like to know protected static Collection getTopTerms(TermFreqVector tfv, int maxTerms){ String[] terms = tfv.getTerms(); int[] tFreqs = tfv.getTermFrequencies(); List result = new ArrayList(terms.length); for (int i = 0; i < tFreqs.length; i++) { TermFrq tf = new TermFrq(terms[i], tFreqs[i]); result.add(tf); } Collections.sort(result, new FreqComparator()); if(maxTerms < result.size()){ result = result.subList(0, maxTerms); } return result; } /Class for objects to hold the term/freq pairs/ static class TermFrq{ private String term; private int freq; public TermFrq(String term,int freq){ this.term = term; this.freq = freq; } public String getTerm(){ return this.term; } public int getFreq(){ return this.freq; } } /*Comparator to compare the objects by the frequency*/ class FreqComparator implements Comparator{ public int compare(Object pair1, Object pair2){ int f1 = ((TermFrq)pair1).getFreq(); int f2 = ((TermFrq)pair2).getFreq(); if(f1 > f2) return 1; else if(f1 < f2) return -1; else return 0; } } Explanations and corrections i will very much appreciate, and also if someone else had experience with term frequency extraction and did it better way, I am opened to all suggestions! Please help!!!! Thanx!

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• Have you considered doing revenue sharing to fund development of a mobile app? How would you do it?

  - by Brennan

  I am looking to build multiple mobile apps which leverage existing content and resources by enabling these mobile apps with web services. I will duplication much of the same features which are also in place and add more features that are possible on a mobile device like address book, maps and calendar integration to make the service much more useful. To fund these projects I see that I have 2 options. First I could simply quote them for the project based on my hourly rate and the estimate in hours that I will take the to complete the job. That may be a high number. The second option would be to do shared revenue with ads placed in the app. I could then take a percentage of any revenue that is generated from the app. There is also a hybrid where I might charge for a percentage of the estimated quote and then take a percentage of the revenue sharing. So my question is how much should I propose for the revenue sharing? Should it be 30%? Or maybe I should make it 70% up to a point that a certain dollar amount is reached? And should the revenue sharing agreement be for 12 months, 24 months or more? Should I include in the proposal an agreement that they will help promote this app with their content and resources? Ultimately this system will benefit both sides because it extends their reach into the mobile space instead of where they are currently with just print and web. I have tried to find some examples with a few Google searches but I keep hitting content about the Google and Apple revenue sharing models. I would like to get some solid examples that are working to compare against so that my proposal do build these apps is not completely off base.

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• one two-directed tcp socket of two one-directed? (linux, high volume, low latency)

  - by osgx

  Hello I need to send (interchange) a high volume of data periodically with the lowest possible latency between 2 machines. The network is rather fast (e.g. 1Gbit or even 2G+). Os is linux. Is it be faster with using 1 tcp socket (for send and recv) or with using 2 uni-directed tcp sockets? The test for this task is very like NetPIPE network benchmark - measure latency and bandwidth for sizes from 2^1 up to 2^13 bytes, each size sent and received 3 times at least (in teal task the number of sends is greater. both processes will be sending and receiving, like ping-pong maybe). The benefit of 2 uni-directed connections come from linux: http://lxr.linux.no/linux+v2.6.18/net/ipv4/tcp_input.c#L3847 3847/* 3848 * TCP receive function for the ESTABLISHED state. 3849 * 3850 * It is split into a fast path and a slow path. The fast path is 3851 * disabled when: ... 3859 * - Data is sent in both directions. Fast path only supports pure senders 3860 * or pure receivers (this means either the sequence number or the ack 3861 * value must stay constant) ... 3863 * 3864 * When these conditions are not satisfied it drops into a standard 3865 * receive procedure patterned after RFC793 to handle all cases. 3866 * The first three cases are guaranteed by proper pred_flags setting, 3867 * the rest is checked inline. Fast processing is turned on in 3868 * tcp_data_queue when everything is OK. All other conditions for disabling fast path is false. And only not-unidirected socket stops kernel from fastpath in receive

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• Abstracting the interpretation of MVC checkboxes values received by the FormsCollection object

  - by Simon_Weaver

  In ASP.NET MVC a checkbox is generated by the HtmlHelper code here: <%= Html.CheckBox("List_" + mailingList.Key, true) %> as this HTML: <input id="List_NEW_PRODUCTS" name="List_NEW_PRODUCTS" type="checkbox" value="true" /> <input name="List_NEW_PRODUCTS" type="hidden" value="false" /> In case you're wondering why is there an extra hidden field? - then read this. Its definitely a solution that makes you first think 'hmmmmm' but then you realize its a pretty elegant one. The problem I have is when I'm trying to parse the data on the backend. Well its not so much of a problem as a concern if anything in future were to change in the framework. If I'm using the built in binding everything is great - its all done for me. But in my case I'm dynamically generating checkboxes with unknown names and no corresponding properties in my model. So i end up having to write code like this : if (forms["List_RETAIL_NOTIFICATION"] == "true,false") { } or this: if (forms.GetValues("List_RETAIL_NOTIFICATION")[0] == "true") { } Both of which i still look at and cringe - especially since theres no guarantee this will always be the return value. I'm wondering if theres a way to access the layer of abstraction used by the model binders - or if I'm stuck with my controller 'knowing' this much about HTTP POST hacks. Yes I'm maybe being a little picky - but perhaps theres a better clever way using the model binders that I can employ to read dynamically created checkbox parameters. In addition i was hoping this this post might help others searcheing for : "true,false". Even though I knew why it does this I just forgot and it took me a little while to realize 'duh'. FYI: I tried another few things, and this is what I found : forms["List_RETAIL_NOTIFICATION"] evaluates to "true,false" forms.GetValues("List_RETAIL_NOTIFICATION")[0] evaluates to "true" (forms.GetValue("List_RETAIL_NOTIFICATION").RawValue as string[])[0] evaluates to "true" forms.GetValues("List_RETAIL_NOTIFICATION").FirstOrDefault() evaluates to "true"

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• Why not put all braces inline in C++/C#/Java/javascript etc.?

  - by DanM

  Of all the conventions out there for positioning braces in C++, C#, Java, etc., I don't think I've ever seen anyone try to propose something like this: public void SomeMethod(int someInput, string someOtherInput) { if (someInput > 5) { var addedNumber = someInput + 5; var subtractedNumber = someInput - 5; } else { var addedNumber = someInput + 10; var subtractedNumber = someInput; } } public void SomeOtherMethod(int someInput, string someOtherInput( { ... } But why not? I'm sure it would take some getting used to, but I personally don't have any difficulty following what's going on here. I believe indentation is the dominant factor in being able to see how code is organized into blocks and sub-blocks. Braces are just visual noise to me. They are these ugly things that take up lines where I don't want them. Maybe I just feel that way because I was weened on basic (and later VB), but I just don't like braces taking up lines. If I want a gap between blocks, I can always add an empty line, but I don't like being forced to have gaps simply because the convention says the closing brace needs to be on its own line. I made this a community wiki because I realize this is not a question with a defined answer. I'm just curious what people think. I know that no one does this currently (at least, not that I've seen), and I know that the auto-formatter in my IDE doesn't support it, but are there are any other solid reasons not to format code this way, assuming you are working with a modern IDE that color codes and auto-indents? Are there scenarios where it will become a readability nightmare? Better yet, are you aware of any research on this?

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• Windows/C++: how to use a COM dll which is not registered

  - by Albert

  Hi, In our application, we need to use a COM dll (namely msdia100.dll) which was not registered in the system before. Earler, we have just called the DLL by calling its DllRegisterServer via this code: // Register DIA DLL required by Breakpad std::string diaLibPath = "msdia100"; HMODULE diaLib = LoadLibrary(diaLibPath.c_str()); if( diaLib == NULL ) { errors << "Cannot load DLL " << diaLibPath << endl; return; } typedef HRESULT ( __stdcall * regServer_t )(void); regServer_t regServer = (regServer_t)GetProcAddress(diaLib, "DllRegisterServer"); if( regServer == NULL ) { errors << "Cannot get method DllRegisterServer from " << diaLibPath << endl; FreeLibrary(diaLib); return; } if( regServer() != S_OK ) { errors << "Cannot call DllRegisterServer from " << diaLibPath << endl; } FreeLibrary(diaLib); This doesn't work anymore on Windows 7 (maybe also Vista, didn't tried) because to call this function, it needs Administrator privileges. All solutions to this problem I have found where about getting those Admin rights. That is no possible solution for us because our application must also work if the user is not able to get those Admin rights. It is also no solution for us to suddenly need an installer for our application which registeres this DLL. So, what possibilities are there? How can I use this DLL without Admin rights? Do I have to recode COM which works without the need to register a DLL first?

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• Where is the errnos defined? Example linux c/c++ program for i2c.

  - by Johan

  Hi When something goes wrong in a classic linux c/c++ software we have the magic variable errno that gives us a clue on what just went wrong. But where is those errors defined? Let's take a example (it's actually a piece from a Qt app, therefore the qDebug()). if (ioctl(file, I2C_SLAVE, address) < 0) { int err = errno; qDebug() << __FILE__ << __FUNCTION__ << __LINE__ << "Can't set address:" << address << "Errno:" << err << strerror(err); .... The next step is to look at what that errno was so we can decide if we just quit or try to do something about the problem. So we maybe add a if or switch at this point. if (err == 9) { // do something... } else { //do someting else } And my question is where to find the errors that "9" represents? I don't like that kind of magic numbers in my code. /Thanks

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• WPF ResourceDictionary and DynamicResource

  - by lanicor

  i am new to WPF so maybe this will be "noob" question but i can't find answer to it (and it seems so easy)... well i am programing WPF app and i want to use smth similar to css for webpages, so i found ResourceDictionary and tried to use it... I have main window in which i create Frame and on click some UserControl is loaded to that same Frame.I include my ResourceDictionary (root/style/Styles.xaml) to my main window like this: <Window.Resources> <ResourceDictionary x:Key="styles" Source="style/Styles.xaml" /> </Window.Resources> in which i have: <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Style x:Key="ProductsRequired" TargetType="{x:Type Label}"> <Setter Property="Height" Value="28" /> ... I don't use it on my main window but want to use it on my UserControls, which are loaded to that main window and i try to use it like this: <Label Name="product1" Style="{DynamicResource ProductsRequired}" /> Warning i am getting all the time is: The resource "ProductsRequired" could not be resolved. I even tried including Styles to my UserControl <UserControl.Resources> <ResourceDictionary x:Key="styles" Source="../style/Styles.xaml" /> </UserControl.Resources> and nothing happens... Well my question is long but i wanted to be clear... :) P.S. all that logic works in C# code btw private ResourceDictionary myStyles = new ResourceDictionary(); Style ProductsRequired = myStyles["ProductsRequired"] as Style; product1.Style = ProductsRequired;

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• Finding missing files by checksum

  - by grw

  Hi there, I'm doing a large data migration between two file systems (let's call them F1 and F2) on a Linux system which will necessarily involve copying the data verbatim into a differently-structured hierarchy on F2 and changing the file names. I'd like to write a script to generate a list of files which are in F1 but not in F2, i.e. the ones which weren't copied by the migration script into the new hierarchy, so that I can go back and migrate them manually. Unfortunately for reasons not worth going into, the migration script can't be modified to list files that it doesn't migrate. My question differs from this previously answered one because of the fact that I cannot rely on filenames as a comparison. I know the basic outline of the process would be: Generate a list of checksums for all files, recursing through F1 Do the same for F2 Compare the lists and generate a negative intersection of the checksums, ignoring the file names, to find files which are in F1 but not in F2. I'm kind of stuck getting past that stage, so I'd appreciate any pointers on which tools to use. I think I need to use the 'comm' command to compare the list of file checksums, but since md5sum, sha512sum and the like put the file name next to the checksum, I can't see a way to get it to bring me a useful comparison. Maybe awk is the way to go? I'm using Red Hat Enterprise Linux 5.x. Thanks.

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• Problem logging in and changing permissions in Facebook

  - by kujawk

  Hi everybody, I've got a piece of code that logs into Facebook, gets a session, sets status_update and offline_access permission if they are not set, and gets a new session with the newly set permissions. This code used to work fine but now I'm getting error 100 "One of the parameters specified was missing or invalid" as a response to the second call to get session and I can't figure out why. Here's the sequence in detail: CREATE TOKEN restserver.php?method=auth.createToken&api_key=[our key]&v=1.0&format=JSON&sig=[sig created with our secret] response: new token LOGIN m.facebook.com/login.php?api_key=[our key]&v=1.0&auth_token=[token created above] login screen loads and user successfully logs in with their username/password. GET SESSION restserver.php?method=auth.getSession&api_key=[our key]&v=1.0&format=JSON&auth_token=token created above&sig=[sig created with our secret] response: session key with expiration date and a secret CHECK/AUTHORIZE PERMISSIONS restserver.php?method=users.hasAppPermission&api_key=[our key]&v=1.0&format=JSON&ext_perm=status_update&call_id=[proper id]&session_key=[key returned above]&sig=[sig created with secret returned for get session] response: 0 m.facebook.com/authorize.php?api_key=[our key]&v=1.0&ext_perm=status_update authorization screen loads and user authorizes Same steps for status_update CREATE NEW TOKEN Same steps as done to create the first token LOGIN m.facebook.com/login.php?api_key=[our key]&v=1.0&auth_token=[new token] user is already logged in, redirected to their homepage GET NEW SESSION restserver.php?method=auth.getSession&api_key=[our key]&format=JSON&auth_token=[new token]&sig=[sig created with our secret] response: error 100 - missing or invalid parameter. Of course it doesn't tell me which one. Anybody have any ideas what I'm doing wrong here? I tried skipping the second login and going right to creating the new session and that didn't work. The only thing that seems to work is logging out the user after they've authorized the permissions and having them log back in again. I'd like to avoid this if possible. Can you have two outstanding sessions at one time? This code used to work but I'm thinking maybe something changed on Facebook's end that I'm not aware of. Thanks, kris

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• How to use a VB usercontrol on a C# page?

  - by ks78

  Hopefully someone will be able to point me in the right direction. I've created a usercontrol in VB that handles paging more efficiently than the DataPager (at least for very large datasets). I'd like to use it in a C# project, but I've been having trouble getting it to work. I've tried simply adding PagingControl.ascx to the C# project, but when I do that the markup and VB code behind don't seem to see each other. --Is this a namespace issue? I've tried adding the PagingControl.ascx to its own VB project, then adding that project to the C# project's solution, as well as a reference. --That almost works. I can register the PagingControl usercontrol in the markup. I can access the usercontrol's properties in the code behind, but any property that involves the UI of the usercontrol fails. Its seems as if the usercontrol's form hasn't had a chance to load by the time the C# page's Page_Load event handler fires. --Maybe this is an "order of operations" problem? At what point in the C# page's lifetime should a usercontrol's form be loaded? If anyone has any ideas or insight, I'd really appreciate it. Thanks in advance.

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• What is the merit of the "function" type (not "pointer to function")

  - by anatolyg

  Reading the C++ Standard, i see that there are "function" types and "pointer to function" types: typedef int func(int); // function typedef int (*pfunc)(int); // pointer to function typedef func* pfunc; // same as above I have never seen the function types used outside of examples (or maybe i didn't recognize their usage?). Some examples: func increase, decrease; // declares two functions int increase(int), decrease(int); // same as above int increase(int x) {return x + 1;} // cannot use the typedef when defining functions int decrease(int x) {return x - 1;} // cannot use the typedef when defining functions struct mystruct { func add, subtract, multiply; // declares three member functions int member; }; int mystruct::add(int x) {return x + member;} // cannot use the typedef int mystruct::subtract(int x) {return x - member;} int main() { func k; // the syntax is correct but the variable k is useless! mystruct myobject; myobject.member = 4; cout << increase(5) << ' ' << decrease(5) << '\n'; // outputs 6 and 4 cout << myobject.add(5) << ' ' << myobject.subtract(5) << '\n'; // 9 and 1 } Seeing that the function types support syntax that doesn't appear in C (declaring member functions), i guess they are not just a part of C baggage that C++ has to support for backward compatibility. So is there any use for function types, other than demonstrating some funky syntax?

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• IE 7 activex object (or xmlhttprequest?) open method using POST takes 20-30 seconds to return

  - by Toddeman

  i have a problem that only shows itself in IE7. its a simple ajax call. i got my object (accounting for the browser) so in 7 i SHOULD have an ActiveXObject. when i call open with POST, it takes 20-30 seconds to return. i am using a TON of GET calls to populate information and all of these work (finally, after some bug fixing), but i am NOT a web developer so much like the other bugs i had to fix, i figured i was just missing another IE anomaly. this is not a consistent bug either, which makes it harder to find for me. most times the POST functions like it does in Firefox or Chrome, but maybe 1 out of 4 or 5 will take 20-30 seconds to return. it DOES return correctly when it returns, it just takes a long time. am i missing something simple? or is there a smarter way for me to find out exactly what is going on (like the equivalent of the firebug 'net' tab for windows?).

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• Retrieve the Value of An Integer Variable

  - by Abluescarab

  This is probably easily figured out (I feel very stupid right now), but I can't find a solution anywhere, for some reason. Perhaps I'm not searching for the right thing. And maybe it's in some beginner tutorial I haven't watched. Anyway, I was wondering how to retrieve the value of an integer variable in C++? I know you can use cin.getline() for string variables, but I received an error message when I attempted that with an integer variable (and rightfully so, I know it was wrong, but I was looking for a solution). My project is a Win32 console application. What I'm trying to do is ask a user to input a number, stored in the variable n. Then I take the value of n and perform various math functions with it. In my header file, I have string, windows, iostream, stdio, math, and fstream. Do I need to add another library? There's not much more to tell. I can post my code if I must. EDIT: cout << "TEST SINE"; cout << "\nPlease enter a number.\n\n"; cin >> n; break; Here's the code I'm trying to use. Is this all I need to do? If so, how do I incorporate the variable so I can test it using sin, cos, and tan? Yet again, thanks ahead of time.

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• Bug with DataBinding in WPF Host in Winforms?

  - by Tigraine

  Hi Guys, I've spent far too much time with this and can't find the mistake. Maybe I'm missing something very obvious or I may have just found a bug in the WPF Element Host for Winforms. I am binding a ListView to a ObeservableList that lives on my ProductListViewModel. I'm trying to implement searching for the ListView with the general Idea to just change the ObservableList with a new list that is filtered. Anyway, the ListView Binding code looks like this: <ListView ItemsSource="{Binding Path=Products}" SelectedItem="{Binding Path=SelectedItem}" SelectionMode="Single"> <ListView.ItemContainerStyle> <Style TargetType="{x:Type ListViewItem}"> <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"></Setter> </Style> </ListView.ItemContainerStyle> <ListView.ItemTemplate> <DataTemplate> <TextBlock Text="{Binding Name}"></TextBlock> </DataTemplate> </ListView.ItemTemplate> </ListView> And the ViewModel code is as vanilla as it can get: private ObservableCollection<ProductViewModel> products; public ObservableCollection<ProductViewModel> Products { get { return products; } private set { if (products != value) { products = value; OnPropertyChanged("Products"); } } } Now the problem here: Once I debug into my OnPropertyChanged method, I can see that there are no subscribers to the PropertyChanged event (it's null), so nothing happens on the UI.. I already tried Mode=TwoWay and other Binding modes, it seems I can't get the ListView to subscribe to the ItemsSource... Can anyone help me with this? I'm just about to forget about the ElemenHost and just do it in Winforms greetings Daniel

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• MySQL: How to pull information from multiple tables based on information in other tables?

  - by Greg

  Ok, I have 5 tables which I need to pull information from based on one variable. gameinfo id | name | platforminfoid gamerinfo id | name | contact | tag platforminfo id | name | abbreviation rosterinfo id | name | gameinfoid rosters id | gamerinfoid | rosterinfoid The 1 variable would be gamerinfo.id, which would then pull all relevant data from gamerinfo, which would pull all relevant data from rosters, which would pull all relevant data from rosterinfo, which would pull all relevant data from gameinfo, which would then pull all relevant data from platforminfo. Basically it breaks down like this: gamerinfo contains the gamers basic information. rosterinfo contains basic information about the rosters (ie name and the game the roster is aimed towards) rosters contains the actual link from the gamer to the different rosters (gamers can be on multiple rosters) gameinfo contains basic information about the games (ie name and platform) platform info contains information about the different platforms the games are played on (it is possible for a game to be played on multiple platforms) I am pretty new to SQL queries involving JOINs and UNIONs and such, usually I would just break it up into multiple queries but I thought there has to be a better way, so after looking around the net, I couldn't find (or maybe I just couldn't understand what I was looking at) what I was looking for. If anyone can point me in the right direction I would be most grateful.

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• What does it mean for an OS to "execute within user processes"? Do any modern OS's use that approach

  - by Chris Cooper

  I have recently become interested in operating system, and a friend of mine lent me a book called Operating Systems: Internals and Design Principles (I have the third edition), published in 1998. It's been a very interesting book so far, but I have come to the part dealing with process control, and it's using UNIX System V as one of its examples of an operating system that executes within user processes. This concept has struck me as a little strange. First of all, does this mean that OS instructions and data are stored in each user of the processes? Probably not, because that would be an absurdly redundant scheme. But if not, then what does it mean to "execute within" a user process? Do any modern operating systems use this approach? It seems much more logical to have the operating system execute as its own process, or even independently of all processes, if you're short on memory. All the inter-accessiblilty of process data required for this layout seems to greatly complicate things. (But maybe that's just because I don't quite get the concept ;D) Here is what the book says: "Execution within User Processes: An alternative that is common with operation systems on smaller machines is to execute virtually all operating system software in the context of a user process. ... "

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• SQL Structure of DB table with different types of columns

  - by Dmitry Dvornikov

  I have a problem with the optimization of the structure of the database. I'll try to explain it exactly. I create a project, where we can add different values??, but this values must have different types of the columns in the database (eg, int, double , varchar). What is the best way to store the different types of values ??in the database. In the project I'm using Propel 1.6. The point is availability to add value with 'int', 'varchar' and other columns types, to search the table was efficient. In total, I have two ideas. The first is to create a table of "value", which will have columns: "id ", "value_int", "value_double", "value_varchar", etc - with the corresponding column types. Depending on the type of values??, records will be saved with the value in the appropriate column (the rest will be NULL). The second solution is to create separate tables such as "value_int", "value_varchar" etc. There would be columns: "id", "value", which correspond to the relevant types of "value" (ie, such as int, varchar, etc). I must admit that I do not believe any of the above solutions, originally I was thinking about one table "value", where the column would be a "text" type - but this solution would probably be even worse. I would like to know your opinion on this topic, maybe something else would be better. Thanks in advance. EDIT: For example : We have three tables: USER: [table of users] * id * name FIELD: [table of profile fields - where the column 'type' is the type of field, eg int or varchar) * id * type * name VALUE : * id * User_id - ( FK user.id ) * Field_id - ( FK field.id ) * value So we have in each row an user in USER table, and the profile is stored in the VALUE table. Bit each profile field may have a different type (column 'type' in the FIELD table), and based on that I would want this value to add to the appropriate column of the appropriate type.

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• How to test if a user has SELECTED a file to upload ?

  - by Tristan

  Hello, on a page, i have : if (!empty($_FILES['logo']['name'])) { $dossier = 'upload/'; $fichier = basename($_FILES['logo']['name']); $taille_maxi = 100000; $taille = filesize($_FILES['logo']['tmp_name']); $extensions = array('.png', '.jpg', '.jpeg'); $extension = strrchr($_FILES['logo']['name'], '.'); if(!in_array($extension, $extensions)) { $erreur = 'ERROR you must upload the right type'; } if($taille>$taille_maxi) { $erreur = 'too heavy'; } if(!empty($erreur)) { ....................... } The problem is, if the users wants to edit information WITHOUT uploading a LOGO, it raises an error : 'error you must upload the right type' So, if a user didn't put anything in the inputbox in order to upload it, i don't want to enter in these conditions test. i tested : if (!empty($_FILES['logo']['name']) and if (isset($_FILES['logo']['name']) but both doesn't seems to work. Any ideas? edit : maybe i wasn't so clear, i don't want to test if he uploaded a logo, i want to test IF he selected a file to upload, because right now, if he doesn't select a file to upload, php raises an error telling he must upload with the right format. thanks.

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• JQuery: how to store records id for data from ajax query in dynamicly created html elements

  - by grapkulec

  Probably question title is rather cryptic but I will try to explain myself here so please bare with me :) Let's assume this configuration: server-side is PHP application responding for requests with data (list of items, single item details, etc.) in json format client-side is JQuery application sending ajax request to that PHP app and creating html content corresponding with received data So, for example: client requests "list of all animals with names staring with 'A'", gets the json response from server, and for every "animal" creates some html gizmo like div with animal description or something like that. It doesn't really matter what html element it will be but it has to point exactly to specific record by "containing" id of that record. And here is my dilemma: is it good solution to use "id" property for that? So it would be like: <div id="10" class="animal"> <p> This is animal of very mysterious kind... </p> </div> <div id="11" class="animal"> <p> And this one is very common to our country... </p> </div> where id="10" is of course indication that this is representation of record with id = 10. Or maybe I should store this record id in some custom made tag like <record_id>10</record_id> and leave an "id" strictly for what it was meant to be (css selector)? I need that record id for further stuff like updating database with some user input or deleting some of "animals" or creating new ones or anything that will be needed. All manipulations will be done with JQuery and ajax requests and responses will be visualized also with dynamic creation of html interface. I'm sure that somebody had to deal with that kind of stuff before so I would be grateful for some tips on that topic.

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