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  • Threading calls to web service in a web service - (.net 2.0)

    - by Ryan Ternier
    Got a question regarding best practices for doing parallel web service calls, in a web service. Our portal will get a message, split that message into 2 messages, and then do 2 calls to our broker. These need to be on separate threads to lower the timeout. One solution is to do something similar to (pseudo code): XmlNode DNode = GetaGetDemoNodeSomehow(); XmlNode ENode = GetAGetElNodeSomehow(); XmlNode elResponse; XmlNode demResponse; Thread dThread = new Thread(delegate { //Web Service Call GetDemographics d = new GetDemographics(); demResponse = d.HIALRequest(DNode); }); Thread eThread = new Thread(delegate { //Web Service Call GetEligibility ge = new GetEligibility(); elResponse = ge.HIALRequest(ENode); }); dThread.Start(); eThread.Start(); dThread.Join(); eThread.Join(); //combine the resulting XML and return it. //Maybe throw a bit of logging in to make architecture happy Another option we thought of is to create a worker class, and pass it the service information and have it execute. This would allow us to have a bit more control over what is going on, but could add additional overhead. Another option brought up would be 2 asynchronous calls and manage the returns through a loop. When the calls are completed (success or error) the loop picks it up and ends. The portal service will be called about 50,000 times a day. I don't want to gold plate this sucker. I'm looking for something light weight. The services that are being called on the broker do have time out limits set, and are already heavily logged and audited, so I'm not worried on that part. This is .NET 2.0 , and as much as I would love to upgrade I can't right now. So please leave all the goodies of 2.0 out please.

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  • How to emulate mod_rewrite in PHP

    - by Tyler Crompton
    I have a few URLs that I want to map to certain files via PHP. Currently, I am just using mod_rewrite in Apache. However, my application is getting too large for the rewriting to be done with regular expressions. So I created a file router.php that does the rewriting. I understand to do a redirect I could just send the Location: header. However, I don't always want to do a redirect. For example, I may want /api/item/ to map to the file /herp/derp.php relative to the document root. I need to preserve the HTTP method as well. "No problem," I thought. I made my .htaccess have the following snippet. RewriteEngine On RewriteRule ^api/item/$ /cgi-bin/router.php [L] And my router.php file looks as follows: <?php $uri = parse_url($_SERVER['REQUEST_URI']); $query = isset($uri['query']) ? $uri['query'] ? array(); // some code that modifies the query require_once "{$_SERVER['DOCUMENT_ROOT']}/herp/derp.php?" . http_build_query($query); ?> However, this doesn't work, because the OS is looking for a file named derp.php?some=query. How can I simulate a rewrite rule such as RewriteRule ^api/item/$ /herp/derp/ [L] in PHP. In other words, how do I tell the server to process a different URL than requested and preserve the query and HTTP method without causing a redirect? Note: Using variables set in router.php is less than desirable and is bad structure since it's only supposed to be responsible for handling URLs. I am open to using a light-weight third party solution.

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  • Existentials and Scrap your Boilerplate

    - by finnsson
    I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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  • javax.xml.ws.soap.SOAPFaultException: Could not send Message - at JaxWsClientProxy.invoke - caused by HTTP response code: 401 for URL

    - by Mikkis
    I moved a working code from dev to test and encountered the following error(s) in test: javax.xml.ws.soap.SOAPFaultException: Could not send Message. at org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:143) ...... at org.apache.cxf.interceptor.MessageSenderInterceptor$MessageSenderEndingInterceptor.handleMessage(MessageSenderInterceptor.java:64) at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:236) at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:472) at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:302) at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:254) at org.apache.cxf.frontend.ClientProxy.invokeSync(ClientProxy.java:73) at org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:123) at $Proxy739.copyIntoItems(Unknown Source) Caused by: java.io.IOException: Server returned HTTP response code: 401 for URL: http:///_vti_bin/Copy.asmx at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1436) at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:379) at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.handleResponseInternal(HTTPConduit.java:2046) Environment specs: Java 1.6 Tomcat 6 Eclipse Helios Maven2 CXF 2.2.3 As a background work, tried to explore about the error in similar category bad URL (ruled out as i am using same URL in dev and test. and the url, userid, password are all accessible from both the machines), connection timeout( error is not 404 or it doesnt specify connection timed out... it says 401 response code for url) Checked if all the jars and same versions are included in the test environment. Can someone shed some light to understand and resolve the error? please let me know if any more details are to be included.

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  • Am I going the right way to make login system secure with this simple password salting?

    - by LoVeSmItH
    I have two fields in login table password salt And I have this little function to generate salt function random_salt($h_algo="sha512"){ $salt1=uniqid(rand(),TRUE); $salt2=date("YmdHis").microtime(true); if(function_exists('dechex')){ $salt2=dechex($salt2); } $salt3=$_SERVER['REMOTE_ADDR']; $salt=$salt1.$salt2.$salt3; if(function_exists('hash')){ $hash=(in_array($h_algo,hash_algos()))?$h_algo:"sha512"; $randomsalt=hash($hash,md5($salt)); //returns 128 character long hash if sha512 algorithm is used. }else{ $randomsalt=sha1(md5($salt)); //returns 40 characters long hash } return $randomsalt; } Now to create user password I have following $userinput=$_POST["password"] //don't bother about escaping, i have done it in my real project. $static_salt="THIS-3434-95456-IS-RANDOM-27883478274-SALT"; //some static hard to predict secret salt. $salt=random_salt(); //generates 128 character long hash. $password =sha1($salt.$userinput.$static_salt); $salt is saved in salt field of database and $password is saved in password field. My problem, In function random_salt(), I m having this FEELING that I'm just making things complicated while this may not generate secure salt as it should. Can someone throw me a light whether I m going in a right direction? P.S. I do have an idea about crypt functions and like such. Just want to know is my code okay? Thanks.

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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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  • Convert a Dynamic[] construct to a numerical list

    - by Leo Alekseyev
    I have been trying to put together something that allows me to extract points from a ListPlot in order to use them in further computations. My current approach is to select points with a Locator[]. This works fine for displaying points, but I cannot figure out how to extract numerical values from a construct with head Dynamic[]. Below is a self-contained example. By dragging the gray locator, you should be able to select points (indicated by the pink locator and stored in q, a list of two elements). This is the second line below the plot. Now I would like to pass q[[2]] to a function, or perhaps simply display it. However, Mathematica treats q as a single entity with head Dynamic, and thus taking the second part is impossible (hence the error message). Can anyone shed light on how to convert q into a regular list? EuclideanDistanceMod[p1_List, p2_List, fac_: {1, 1}] /; Length[p1] == Length[p2] := Plus @@ (fac.MapThread[Abs[#1 - #2]^2 &, {p1, p2}]) // Sqrt; test1 = {{1.`, 6.340196001221532`}, {1.`, 13.78779876355869`}, {1.045`, 6.2634018978377295`}, {1.045`, 13.754947081416544`}, {1.09`, 6.178367702583522`}, {1.09`, 13.72055251752498`}, {1.135`, 1.8183153704413153`}, {1.135`, 6.082497198000075`}, {1.135`, 13.684582525399742`}, {1.18`, 1.6809452373465104`}, {1.18`, 5.971583107298081`}, {1.18`, 13.646996905469383`}, {1.225`, 1.9480537697339537`}, {1.225`, 5.838386922625636`}, {1.225`, 13.607746407088161`}, {1.27`, 2.1183174369679234`}, {1.27`, 5.669799095595362`}, {1.27`, 13.566771130126131`}, {1.315`, 2.2572975468163463`}, {1.315`, 5.444014254828522`}, {1.315`, 13.523998701347882`}, {1.36`, 2.380307009155079`}, {1.36`, 5.153024664297602`}, {1.36`, 13.479342200528283`}, {1.405`, 2.4941312539733285`}, {1.405`, 4.861423833512566`}, {1.405`, 13.432697814928654`}, {1.45`, 2.6028066447609426`}, {1.45`, 4.619367407525507`}, {1.45`, 13.383942212133244`}}; DynamicModule[{p = {1.2, 10}, q = {1.3, 11}}, q := Dynamic@ First@test1[[ Ordering[{#, EuclideanDistanceMod[p, #, {1, .1}]} & /@ test1, 1, #1[[2]] < #2[[2]] &]]]; Grid[{{Show[{ListPlot[test1, Frame -> True, ImageSize -> 300], Graphics@Locator[Dynamic[p]], Graphics@ Locator[q, Appearance -> {Small}, Background -> Pink]}]}, {Dynamic@p}, {q},{q[[2]]}}]]

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  • What could cause these Apache crash errors ?

    - by jacobanderssen
    Hello guys. I had a server crash several days ago. I use Cacti to keep stats: at the time when the server crashed, a huge spike from Load 1 to Load 200 occurred, with over 800 processes in the run queue ( from 300 average). Upon checking /var/log/httpd I notice this: * glibc detected /usr/sbin/httpd: double free or corruption (out): 0x00002b8f3142c2f0 ** Followed by alot of these: [Sat Mar 13 19:20:20 2010] [warn] child process 3090 still did not exit, sending a SIGTERM [Sat Mar 13 19:20:20 2010] [warn] child process 3091 still did not exit, sending a SIGTERM Followed by this: ======= Backtrace: ========= /lib64/libc.so.6[0x2b8f1463c2ef] /lib64/libc.so.6(cfree+0x4b)[0x2b8f1463c73b] /usr/lib64/libapr-1.so.0(apr_pool_destroy+0x131)[0x2b8f13f98821] /usr/sbin/httpd[0x2b8f126df47e] /usr/sbin/httpd[0x2b8f126df4ab] /lib64/libpthread.so.0[0x2b8f141b87c0] /etc/httpd/modules/mod_file_cache.so[0x2b8f1cdf00fb] ======= Memory map: ======== And finally a lot of these: [Sat Mar 13 19:20:27 2010] [error] could not make child process 733 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 24560 exit, attempting to continue anyway [Sat Mar 13 19:20:27 2010] [error] could not make child process 31384 exit, attempting to continue anyway I am also noticing one or two lines like this: [Mon Mar 15 01:17:26 2010] [notice] child pid 20765 exit signal Segmentation fault (11) Please help me shed some light on this. Thanks !

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  • Need to exclude results in a MySQL query where two table fields are not of certain values (brain far

    - by DondeEstaMiCulo
    I don't know if I'm just burnt out and can't think, or what... But I can't seem to make this work right... (We're using MySQL 5.1...) I have two tables which have some transactional stuff stored in them. There will be many records per user_id in each table. Table1 and Table2 have a one-to-one relationship with each other. I want to pull records from both tables, but I want to exclude records which have certain values in both tables. I don't care if they both don't have these values, or if just one does, but both tables should not have both values. (Does this make any sense? lol) For example: SELECT t1.id, t1.type, t2.name FROM table1 t1 INNER JOIN table2 t2 ON table.xid = table2.id WHERE t1.user_id = 100 AND (t1.type != 'FOO' AND t2.name != 'BAR') So t1.type is type ENUM with about 10 different options, and t2.name is also type ENUM with 2 options. My expected results would look a little like: 1, FOO, YUM 2, BOO, BAR 3, BOO, YUM But instead, all I'm getting is: 3, BOO, YUM Because it's filtering out all records which has 'FOO' as the type, and 'BAR' as the name. I keep waiting for that D'oh! moment where it hits me and I feel like an idiot for not realizing what I'm doing wrong. But it hasn't come. And I still feel like an idiot, lol. I appreciate any light any of you can shed on this! Many thanks in advance for the help!

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  • With C# 3.0, how to write Interface based code with generic collection?

    - by Deecay
    I want to write code that is decouple and clean, and I know that by programming to an interface instead of the implementation, my code will be more flexible and extensible. So, instead of writing methods like: bool IsProductAvailable(ProductTypeA product); I write methods like: bool IsProductAvailable(IProduct product); As long as my products implement IProduct: class ProductTypeA : IProduct I should be OK. All is well until I start using generic collections. Since C# 3.0 doesn't support covariant and contravariant, even though both ProuctTypeA and ProductTypeB implements IProduct, you cannot put List in List. This is pretty troublesome because a lot of times I want to write something like: bool AreProductsAvailable(List<IProduct> products); So that I can check product avaialbility by writing: List<ProductA> productsArrived = GetDataFromDataabase(); bool result = AreProductsAvailable(productsArrived); And I want to write just one AreProductsAvailable() method that works with all IProduct collections. I know that C# 4.0 is going to support covariant and contravariant, but I also realize that there other libraries that seemed to have the problem solved. For instance, I was trying out ILOG Gantt the gantt chart control, and found that they have a lot of collection intefaces that looks like this: IActivityCollection ILinkCollection So it seems like their approach is wrapping the generic collection with an interface. So instead of "bool AreProductsAvailable(List products);", I can do: bool AreProductsAvailable(IProductCollection products); And then write some code so that IProductCollection takes whatever generic collection of IProduct, be it List or List. However, I don't know how to write an IProductCollection interface that does that "magic". :-< (ashame) .... Could someone shed me some light? This has been bugging me for so long, and I so wanted to do the "right thing". Well, thanks!

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  • lighten background color on button click per binding

    - by one of two
    I want to lighten a buttons background on click. So I did the following: <converter:ColorLightConverter x:Key="colorLightConverter" /> ... <Style BasedOn="{StaticResource default}" TargetType="{x:Type controls:Button}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type controls:Button}"> <ControlTemplate.Triggers> <Trigger Property="IsPressed" Value="True"> <Setter Property="Background"> <Setter.Value> <SolidColorBrush Color="{Binding Path=Background.Color, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource colorLightConverter}}" /> </Setter.Value> </Setter> </Trigger> </ControlTemplate.Triggers> <Border Background="{TemplateBinding Background}" BorderBrush="Transparent" BorderThickness="0"> ... </Border> </ControlTemplate> </Setter.Value> </Setter> </Style> The converter: class ColorLightConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { Color color = (Color)value; System.Drawing.Color lightColor = ControlPaint.Light(System.Drawing.Color.FromArgb(color.A, color.R, color.G, color.B)); return Color.FromArgb(lightColor.A, lightColor.R, lightColor.G, lightColor.B); } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } } But the converter isn't called when I click the button. I think there is anything wrong with the binding, but I can't see the error... Can you help me? Maybe I'm completely wrong. What I basically want to do: When clicking the button, take the current background color and lighten it. Not more...

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  • Treating differential operator as algebraic entity

    - by chappar
    I know that this question is offtopic and don't belong here. But i didn't know somewhere else to ask. So here is the question. I was reading e:the story of a number by Eli Maor, where he treats differential operator as just like any algebraic entity. For example if we have a differential equation like y’’ + 5y’ - 6y = 0. This can be treaed as (D^2 + 5D – 6)y = 0. So, either y = 0 (trivial solution) or (D^2 + 5D – 6) = 0. Factoring out above equation we get (D-1)(D+6)= 0 with solutions as D = 1 and D = -6. Since D does not have any meaning on its own, multiplying by y on both the sides we get Dy = y and Dy = -6y for which the solutions are Ae^x and Be^-6x. Combining these 2 solutions we get Ae^x + Be^-6x. Now my doubt is this approach break when we have an equation like D^2y = 0. Which means y = 0 (again trivial) or D^2 = 0 which means D = 0. Now Dy = y*0 = 0. That means y = C ( a constant). The actual answer should be Cx. I know that it is stupidity to treat D^2 = 0 as D = 0, it led me to doubt the entire process of treating differential equation as algebraic equation. Can someone throw light on this? Or any other site where i might get answer?

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  • correct way of initializing variables

    - by OVERTONE
    ok this is just a shot in the dark but it may be the cause of most of the errors ive gotten. when your initializing something. lets say a smal swing program. would it go liek this variables here { private Jlist contactList; String [] contactArray; ArrayList <String> contactArrayList; ResultSet namesList constructor here public whatever() { GridLayout aGrid = new GridLayout(2,2,10,10); contact1 = new String(); contact2 = new String(); contact3 = new String(); contactArrayList = new ArrayList<String>(); // is something supposed too go in the () of this JList? contactList = new JList(); contactArray = new String[5]; from1 =new JLabel ("From: " + contactArray[1]); gridlayout.add(components)// theres too many components to write onto SO. } // methods here public void fillContactsGui() { createConnection(); ArrayList<String> contactsArrayList = new ArrayList<String>(); while (namesList.next()) { contactArrayList.add(namesList.getString(1)); ContactArray[1] = namesList[1]; } } i know this is probably a huge beginner question but this is the code ive gotten used too. im initializing thigns three and fours times without meaning too because im not sure where they gp. can anyone shed some light on this? p.s. sorry for the messy sample code. i done my best.

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  • algorithm to generate maximum number of character 'A' using keystrokes 'A', CTRL + 'A', CTRL + 'C' and CTRL + 'V'

    - by munda
    This is an interview question from google. I am not able to solve it by myself. Can somebody throw some light? The question goes like this. Write a program to print the sequence of keystrokes such that it generates the maximum number of character 'A's. You are allowed to use only 4 keys: 'A', CTRL + 'A', CTRL + 'C' and CTRL + 'V'. Only N keystrokes are allowed. All CTRL+ characters are considered as one keystroke, so CTRL+A is one keystroke. e.g.: A, ctrl+A, ctrl+C, ctrl+V generates two As in 4 keystrokes. Edit: CTRL + A is Select All CTRL + C is copy CTRL + V is paste I did some mathematics. For any N, using x numbers of A's , one CTRL+A, one CTRL+C and y CTRL+V, we can generate max ((N-1)/2)^2 numbers of A's. But for some N M, it is better to use as many ^A, ^C and ^V as it doubles the number of As. Edit 2: ^A, ^V and ^C will not overwrite on the existing selection but it will append the copied selection to selected one.

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  • difference between http.context.user and thread.currentprincipal and when to use them?

    - by yamspog
    I have just recently run into an issue running an asp.net web app under visual studio 2008. I get the error 'type is not resolved for member...customUserPrincipal'. Tracking down various discussion groups it seems that there is an issue with Visual Studio's web server when you assign a custom principal against the Thread.CurrentPrincipal. In my code, I now use... HttpContext.Current.User = myCustomPrincipal //Thread.CurrentPrincipal = myCustomPrincipal I'm glad that I got the error out of the way, but it begs the question "What is the difference between these two methods of setting a principal?". There are other stackoverflow questions related to the differences but they don't get into the details of the two approaches. I did find one tantalizing post that had the following grandiose comment but no explanation to back up his assertions... Use HttpConext.Current.User for all web (ASPX/ASMX) applications. Use Thread.CurrentPrincipal for all other applications like winForms, console and windows service applications. Can any of you security/dot.net gurus shed some light on this subject?

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  • how to extract information from JSON using jQuery

    - by Richard Reddy
    Hi, I have a JSON response that is formatted from my C# WebMethod using the JavascriptSerializer Class. I currently get the following JSON back from my query: {"d":"[{\"Lat\":\"51.85036\",\"Long\":\"-8.48901\"},{\"Lat\":\"51.89857\",\"Long\":\"-8.47229\"}]"} I'm having an issue with my code below that I'm hoping someone might be able to shed some light on. I can't seem to get at the information out of the values returned to me. Ideally I would like to be able to read in the Lat and Long values for each row returned to me. Below is what I currently have: $.ajax({ type: "POST", url: "page.aspx/LoadWayPoints", data: "{'args': '" + $('numJourneys').val() + "'}", contentType: "application/json; charset=utf-8", dataType: "json", success: function (msg) { if (msg.d != '[]') { var lat = ""; var long = ""; $.each(msg.d, function () { lat = this['MapLatPosition']; long = this['MapLongPosition']; }); alert('lat =' + lat + ', long =' + long); } } }); I think the issue is something to do with how the JSON is formatted but I might be incorrect. Any help would be great. Thanks, Rich

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  • Java Executor: Small tasks or big ones?

    - by Arash Shahkar
    Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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  • Recursive templates: compilation error under g++

    - by Johannes
    Hi, I am trying to use templates recursively to define (at compile-time) a d-tuple of doubles. The code below compiles fine with Visual Studio 2010, but g++ fails and complains that it "cannot call constructor 'point<1::point' directly". Could anyone please shed some light on what is going on here? Many thanks, Jo #include <iostream> #include <utility> using namespace std; template <const int N> class point { private: pair<double, point<N-1> > coordPointPair; public: point() { coordPointPair.first = 0; coordPointPair.second.point<N-1>::point(); } }; template<> class point<1> { private: double coord; public: point() { coord= 0; } }; int main() { point<5> myPoint; return 0; }

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  • Communication between lexer and parser

    - by FredOverflow
    Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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  • Namespace Traversal

    - by RikSaunderson
    I am trying to parse the following sample piece of XML: <?xml version="1.0" encoding="UTF-8"?> <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <soapenv:Body> <d2LogicalModel modelBaseVersion="1.0" xmlns="http://datex2.eu/schema/1_0/1_0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://datex2.eu/schema/1_0/1_0 http://datex2.eu/schema/1_0/1_0/DATEXIISchema_1_0_1_0.xsd"> <payloadPublication xsi:type="PredefinedLocationsPublication" lang="en"> <predefinedLocationSet id="GUID-NTCC-VariableMessageSignLocations"> <predefinedLocation id="VMS30082775"> <predefinedLocationName> <value lang="en">VMS M60/9084B</value> </predefinedLocationName> </predefinedLocation> </predefinedLocationSet> </payloadPublication> </d2LogicalModel> </soapenv:Body> </soapenv:Envelope> I specifically need to get at the contents of the top-level predefinedLocation tag. By my calculations, the correct XPath should be /soapenv:Envelope/soapenv:Body/d2LogicalModel/payloadPublication/predefinedLocationSet/predefinedLocation I am using the following C# code to parse the XML: string filename = "content-sample.xml"; XmlDocument xmlDoc = new XmlDocument(); xmlDoc.Load(filename); XmlNamespaceManager nsmanager = new XmlNamespaceManager(xmlDoc.NameTable); nsmanager.AddNamespace("soapenv", "http://schemas.xmlsoap.org/soap/Envelope"); string xpath ="/soapenv:Envelope/soapenv:Body/d2LogicalModel/payloadPublication/predefinedLocationSet/predefinedLocation"; XmlNodeList itemNodes = xmlDoc.SelectNodes(xpath, nsmanager); However, this keeps coming up with no results. Can anyone shed any light on this, because I feel like I'm banging my head on a brick wall.

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  • How to check if new version of Chrome is available?

    - by serg
    I am trying to build an extension that would notify a user when new version of Chrome is available. I tried to inspect network traffic when Chrome is checking for an update and it is sending a request to http://74.125.95.113/service/update2?w=3:{long_encoded_string} page that returns XML with information I need: <?xml version="1.0" encoding="UTF-8"?> <gupdate xmlns="http://www.google.com/update2/response" protocol="2.0" server="prod"> <daystart elapsed_seconds="31272"/> <app appid="{8A69D345-D564-463C-AFF1-A69D9E530F96}" status="ok"> <updatecheck status="noupdate"/> <ping status="ok"/> </app> </gupdate> Besides sending {long_encoded_string} as URL parameter it is also sending some encoded cookie. Maybe someone familiar with Chrome build process can shed some light on those encoded strings and how to build them? Maybe there is another easier way (I have a feeling that string encoding is a dead end for me)?

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  • Java "Pool" of longs or Oracle sequence with reusable values

    - by Anthony Accioly
    Several months ago I implemented a solution to choose unique values from a range between 1 and 65535 (16 bits). This range is used to generate unique Route Targets suffixes, which for this customer massive network (it's a huge ISP) are a very disputed resource, so any free index needs to become immediately available to the end user. To tackle this requirement I used a BitSet. Allocate on the RT index with set and deallocate a suffix with clear. The method nextClearBit() can find the next available index. I handle synchronization / concurrency issues manually. This works pretty well for a small range... The entire index is small (around 10k), it is blazing fast and can be easy serialized into a Blob field. The problem is, some new devices can handle RTs of 32 bits (range 1 / 4294967296). Which can't be managed with a BitSet (it would, by itself, consume around 600Mb, plus be limited to int range). Even with this massive range available, the client still wants to free available Route Targets for the end user, mainly because the lowest ones (up to 65535) - which are compatible with old routers - are being heavily disputed. Before I tell the customer that this is impossible and he will have to conform with my reusable index for lower RTs (up to 65550) and use a database sequence for the other ones (which means that when the user frees a Route Target, it will not become available again). Would anyone shed some light? Maybe some kind soul already implemented a high performance number pool for Java (6 if it matters), or I am missing a killer feature of Oracle database (11R2 if it matters)... Wishful thinking. Thank you very much in advance.

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  • App is fast on 3GS but slow on 3G

    - by Anthony Chan
    Hi all, I'm new to computer coding and have just finished coding an app and tested it on both 3G and 3GS. On 3GS, it worked as normal as on the simulator. However, when I tried to run it on 3G, the app becomes extremely slow. I'm not sure what's the reason and I hope someone could shed some light on me. Generally, my app has a couple of view controller classes, with one of them being the title page, one being the main page, one is setting, etc. I used a dissolve to transition from the title page to the main page. But even this simple transition shows un-smooth performance on a 3G! My other part of the app involves zooming in to some images by scaling up the images, switching images by push or dissolve upon receiving touch events, saving photos into photo library and storing and retrieving some photos in a folder and some data in a SQlite database, each showing un-smooth actions. Compared with some heavy graphic or heavy maths app, I think mine is pretty simple. I totally have no clue why the app would behave so slow and un-smooth that it is barely useful on a 3G. Any help/ direction would be much appreciated. Thanks for helping out.

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  • Versioning code in two separate projects concurently with subverison

    - by Matt1776
    I have a need to create a library of Object Oriented PHP code that will see much reuse and aspires to be highly flexible and modular. Because of its independent nature I would like it to exist as its own SVN project. I would like to be able to create a new web project, save it in SVN as its own separate project, and include within it the library project code as well. During this process, while coding the web application code and making commits, I may need to add a class to the library. I would like to be able to do so and commit those changes back to the libraries project code. In light of all this I could manage the code in two ways Commit the changes to the library back to a branch of its original base project code and make the branch name relevant to the web project I was using it with Commit the changes to the library back to the original code, growing it in size regardless of any specific references that might exist. I have two questions How can I include this library project code into a new project yet not break the subversion functionality, i.e. allowing me to make changes to each project individually? How I can keep the code synchronized? If I choose the first method of managing the library code I may want to grab changes from another branch and pull it in for use in another.

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  • C++ Storing variables and inheritance

    - by Kaa
    Hello Everyone, Here is my situation: I have an event driven system, where all my handlers are derived from IHandler class, and implement an onEvent(const Event &event) method. Now, Event is a base class for all events and contains only the enumerated event type. All actual events are derived from it, including the EventKey event, which has 2 fields: (uchar) keyCode and (bool)isDown. Here's the interesting part: I generate an EventKey event using the following syntax: Event evt = EventKey(15, true); and I ship it to the handlers: EventDispatch::sendEvent(evt); // void EventDispatch::sendEvent(const Event &event); (EventDispatch contains a linked list of IHandlers and calls their onEvent(const Event &event) method with the parameter containing the sent event. Now the actual question: Say I want my handlers to poll the events in a queue of type Event, how do I do that? x Dynamic pointers with reference counting sound like too big of a solution. x Making copies is more difficult than it sounds, since I'm only receiving a reference to a base type, therefore each time I would need to check the type of event, upcast to EventKey and then make a copy to store in a queue. Sounds like the only solution - but is unpleasant since I would need to know every single type of event and would have to check that for every event received - sounds like a bad plan. x I could allocate the events dynamically and then send around pointers to those events, enqueue them in the array if wanted - but other than having reference counting - how would I be able to keep track of that memory? Do you know any way to implement a very light reference counter that wouldn't interfere with the user? What do you think would be a good solution to this design? I thank everyone in advance for your time. Sincerely, Kaa

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