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• Import CSV to class structure as the user defines

  - by Assimilater

  I have a contact manager program and I would like to offer the feature to import csv files. The problem is that different data sources order the fields in different ways. I thought of programming an interface for the user to tell it the field order and how to handle exceptions. Here is an example line in one of many possible field orders: "ID#","Name","Rank","Address1","Address2","City","State","Country","Zip","Phone#","Email","Join Date","Sponsor ID","Sponsor Name" "Z1234","Call, Anson","STU","1234 E. 6578 S.","","Somecity","TX","United States","012345","000-000-0000","[email protected]","5/24/2010","z12343","Quantum Independence" Notice that in one data field "Name" there is a comma to separate last name and first name and in another there is not. My plan is to have a line for each field (ie ID, Name, City etc.) and a statement "import to" and list box with options like: Don't Import, BusinessJoin Date, First Name, Zip and the program recognizes those as properties of an object... I'd also like the user to be able to record preset field orders so they can re-use them for csv files from the same download source. Then I also need it to check if a record all ready exists (is there a record for Anson Call all ready?) and allow the user to tell it what to do if there is a record (ie mailing address may have changes, so if that field is filled overwrite it, or this mailing address is invalid, leave the current data untouched for this person, overwrite the rest). While I'm capable of coding this...i'm not very excited about it and I'm wondering if there's a tool or set of tools out there to all ready perform most of this functionality... I hope this makes sense...

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• NSOutlineView not redrawing

  - by Septih

  Hello, I have an NSOutlineView with checkboxes. I have the checkbox state bound to a node item with the key shouldBeCopied. In the node item I have the getters and setters like so: -(BOOL)shouldBeCopied { if([[self parent] shouldBeCopied]) return YES; return shouldBeCopied; } -(void)setShouldBeCopied:(BOOL)value { shouldBeCopied = value; if(value && [[self children] count] > 0) [[self delegate] reloadData]; } The idea here is that if the parent is checked, so should the children. The problem I'm having is that when I check the parent, it does not update that view of the children if they are already expanded. I can understand that it should not be updated by the bindings because i'm not actually changing the value. But should reloadData not cause the bindings to re-get the value, thus calling -shouldBeCopied for the children? I have tried a few other things such as -setNeedsDisplay and -reloadItem:nil reloadChildren:YES but none work. I've noticed that the display gets refreshed when I swap to xcode and then back again and that's all I want, so how do I get it to behave that way?

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• What to call factory-like (java) methods used with immutable objects

  - by StaxMan

  When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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• In XSLT, how can you sort using an indirect key?

  - by edholder

  I am having trouble getting xsl:sort to understand the scope of the attributes I am referencing. Here is an XML sample document to illustrate: <Root> <DrinkSelections> <Drink id=1000 name="Coffee"/> <Drink id=1001 name="Water"/> <Drink id=1002 name="Tea"/> <Drink id=1003 name="Almost But Not Quite Entirely Unlike Tea"/> </DrinkSelections> <CustomerOrder> <Drinks> <Drink oid="1001"/> <Drink oid="1002"/> <Drink oid="1003"/> </Drinks> </CustomerOrder </Root> I want to produce a list of drinks (sorted by name) contained in the CustomerOrder. Here is the XSLT code I am fiddling with: <xsl:for-each select="/Root/CustomerOrder/Drinks/Drink"> <xsl:sort select="/Root/DrinkSelections/Drink[@id = @oid]/@name"/> <xsl:variable name=var_oid select="@oid"/> <xsl:value-of select="/Root/DrinkSelections/Drink[@id = $var_oid]/@name"/> </xsl:for-each> Apparently, the xsl:sort command is trying to apply the "oid" attribute to the Drink elements in DrinkSelections, rather than local Drink element. I can get around this using a variable, as in the xsl:value-of statement. But since xsl:sort must be the first statement after the xsl:for-each statement, I can't insert the xsl:variable statement before xsl:sort. Is there a way to explicitly state that the attribute value should be taken from the "local" element?

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• In jQuery datepicker beforeShowDay if fails

  - by michalzuber

  HI. I'm having problem to highlight more days. Somehow the if statement in beforeShowDay isn't true when it should be :( dateString typeof is string and an example is available in the screenshot at http://mikaelz.host.sk/datepicker.png Pasted code: var dates = new Array(); function addDate(date) {if (jQuery.inArray(date, dates) < 0) dates.push(date);} function removeDate(index) {dates.splice(index, 1);} function addOrRemoveDate(date) { var index = jQuery.inArray(date, dates); if (index >= 0) removeDate(index); else addDate(date); } function padNumber(number) { var ret = new String(number); if (ret.length == 1) ret = "0" + ret; return ret; } jQuery(document).ready(function(){ jQuery("#pick-date").datepicker({ onSelect: function(dateText, inst) { addOrRemoveDate(dateText); }, beforeShowDay: function (date){ var year = date.getFullYear(); var month = padNumber(date.getMonth()); var day = padNumber(date.getDate()); var dateString = day + "." + month + "." + year; if (dates.indexOf(dateString) >= 0) { return [true,"ui-state-highlight"]; } return [true, ""]; } }); }); Big thanks for any good ideas what could be wrong.

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• Access is denied. Javascript error on request to secured page

  - by ihorko

  On SomePage.aspx page by javascript (XMLHttpRequest) I call SecuredPage.aspx used next code: var httpRequest = GetXmlHttp(); var url = "https://myhost.com/SecuredPage.aspx"; var params = "param1=" + document.getElementById('param1').value + "&param2=" + document.getElementById('param2').value; httpRequest.open("POST", url, true); httpRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); httpRequest.onreadystatechange = function() { //Call a function when the state changes. if (httpRequest.readyState == 4 && httpRequest.status == 200) { alert(httpRequest.responseText); } } httpRequest.send(params); // HERE ACCESS IS DENIED //--------------------------------------------- function GetXmlHttp() { var xmlhttp = false; if (window.XMLHttpRequest) { xmlhttp = new XMLHttpRequest(); } else if (window.ActiveXObject) // code for IE { try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (E) { xmlhttp = false; } } } return xmlhttp; } It throws Access is denied error. if send to http (http://myhost.com/SecuredPage.aspx), it works fine. How is it possible to resolve that problem. Thanks!

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• unexpected behaviour of object stored in web service Session

  - by draconis

  Hi. I'm using Session variables inside a web service to maintain state between successive method calls by an external application called QBWC. I set this up by decorating my web service methods with this attribute: [WebMethod(EnableSession = true)] I'm using the Session variable to store an instance of a custom object called QueueManager. The QueueManager has a property called ChangeQueue which looks like this: [Serializable] public class QueueManager { ... public Queue<QBChange> ChangeQueue { get; set; } ... where QBChange is a custom business object belonging to my web service. Now, every time I get a call to a method in my web service, I use this code to retrieve my QueueManager object and access my queue: QueueManager qm = (QueueManager)Session[ticket]; then I remove an object from the queue, using qm.dequeue() and then I save the modified query manager object (modified because it contains one less object in the queue) back to the Session variable, like so: Session[ticket] = qm; ready for the next web service method call using the same ticket. Now here's the thing: if I comment out this last line //Session[ticket] = qm; , then the web service behaves exactly the same way, reducing the size of the queue between method calls. Now why is that? The web service seems to be updating a class contained in serialized form in a Session variable without being asked to. Why would it do that? When I deserialize my Queuemanager object, does the qm variable hold a reference to the serialized object inside the Session[ticket] variable?? This seems very unlikely.

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• CSV is actually .... Semicolon Separated Values ... (Excel export on AZERTY)

  - by Bugz R us

  I'm a bit confused here. When I use Excel 2003 to export a sheet to CSV, it actually uses semicolons ... Col1;Col2;Col3 shfdh;dfhdsfhd;fdhsdfh dgsgsd;hdfhd;hdsfhdfsh Now when I read the csv using Microsoft drivers, it expects comma's and sees the list as one big column ??? I suspect Excel is exporting with semicolons because I have a AZERTY keyboard. However, doesn't the CSV reader then also have to take in account the different delimiter ? How can I know the appropriate delimiter, and/or read the csv properly ?? public static DataSet ReadCsv(string fileName) { DataSet ds = new DataSet(); string pathName = System.IO.Path.GetDirectoryName(fileName); string file = System.IO.Path.GetFileName(fileName); OleDbConnection excelConnection = new OleDbConnection (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathName + ";Extended Properties=Text;"); try { OleDbCommand excelCommand = new OleDbCommand(@"SELECT * FROM " + file, excelConnection); OleDbDataAdapter excelAdapter = new OleDbDataAdapter(excelCommand); excelConnection.Open(); excelAdapter.Fill(ds); } catch (Exception exc) { throw exc; } finally { if(excelConnection.State != ConnectionState.Closed ) excelConnection.Close(); } return ds; }

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• WPF bound object update notification

  - by Carlo

  I have a TreeView with a few objects bound to it, let's say something like this: public class House { public List<Room> Rooms { get; set; } public List<Person> People { get; set; } public House() { this.Rooms = new List<Room>(); this.People = new List<Person>(); } public void BuildRoom(string name) { this.Rooms.Add(new Room() { Name = name }); } public void DestroyRoom(string name) { this.Rooms.Remove(new Room() { Name = name }); } public void PersonEnter(string name) { this.People.Add(new Person() { Name = name }); } public void PersonLeave(string name) { this.People.Remove(new Person() { Name = name }); } } public class Room { public string Name { get; set; } } public class Person { public string Name { get; set; } } The TreeView is watching over the House object, whenever a room is built / destroyed or a person enters / leaves, my tree view updates itself to show the new state of the house (I omitted some implementation details for simplicity). What I want is to know the exact moment when this update finishes, so I can do something right there, the thing is that I created an indicator of the selected item, and when something moves, I need to update said indicator's position, that's the reason I need it exactly when the tree view updates. Let me know if you know a solution to this. Also, the code is not perfect (DestroyRoom and PersonLeave), but you get the idea. Thanks!

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• How to write a "thread safe" function in C ?

  - by Andrei Ciobanu

  Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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• Segmentation fault on returning from main (very short and simple code, no arrays or pointers)

  - by Gábor Kovács

  I've been wondering why the following trivial code produces a segmentation fault when returning from main(): //Produces "Error while dumping state (probably corrupted stack); Segmentation fault" #include <iostream> #include <fstream> #include <vector> using namespace std; class Test { vector<int> numbers; }; int main() { Test a; ifstream infile; cout << "Last statement..." << endl; // this gets executed return 0; } Interestingly, 1) if only one of the two variables is declared, I don't get the error, 2) if I declare a vector variable instead of an object with a vector member, everything's fine, 3) if I declare an ofstream instead of an ifstream, again, everything works fine. Something appears to be wrong with this specific combination... Could this be a compiler bug? I use gcc version 3.4.4 with cygwin. Thanks for the tips in advance. Gábor

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• Unit Testing - Algorithm or Sample based ?

  - by ohadsc

  Say I'm trying to test a simple Set class public IntSet : IEnumerable<int> { Add(int i) {...} //IEnumerable implementation... } And suppose I'm trying to test that no duplicate values can exist in the set. My first option is to insert some sample data into the set, and test for duplicates using my knowledge of the data I used, for example: //OPTION 1 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //3 will be added 3 times var values = new List<int> {1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I know 3 is the only candidate to appear multiple times int counter = 0; foreach (int i in set) if (i == 3) counter++; Assert.AreEqual(1, counter); } My second option is to test for my condition generically: //OPTION 2 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //The following could even be a list of random numbers with a duplicate var values = new List<int> { 1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I am not using my prior knowledge of the sample data //the following line would work for any data CollectionAssert.AreEquivalent(new HashSet<int>(values), set); } Of course, in this example, I conveniently have a set implementation to check against, as well as code to compare collections (CollectionAssert). But what if I didn't have either ? This is the situation when you are testing your real life custom business logic. Granted, testing for expected conditions generically covers more cases - but it becomes very similar to implementing the logic again (which is both tedious and useless - you can't use the same code to check itself!). Basically I'm asking whether my tests should look like "insert 1, 2, 3 then check something about 3" or "insert 1, 2, 3 and check for something in general" EDIT - To help me understand, please state in your answer if you prefer OPTION 1 or OPTION 2 (or neither, or that it depends on the case, etc )

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• Should we retire the term "Context"?

  - by MrGumbe

  I'm not sure if there is a more abused term in the world of programming than "Context." A word that has a very clear meaning in the English language has somehow morphed into a hot mess in software development, where the definition where the connotation can be completely different based on what library you happen to be developing in. Tomcat uses the word context to mean the configuration of a web application. Java applets, on the other hand, use an AppletContext to define attributes of the browser and HTML tag that launched it, but the BeanContext is defined as a container. ASP.NET uses the HttpContext object as a grab bag of state - containing information about the current request / response, session, user, server, and application objects. Context Oriented Programming defines the term as "Any information which is computationally accessible may form part of the context upon which behavioral variations depend," which I translate as "anything in the world." The innards of the Windows OS uses the CONTEXT structure to define properties about the hardware environment. The .NET installation classes, however, use the InstallContext property to represent the command line arguments entered to the installation class. The above doesn't even touch how all of us non-framework developers have used the term. I've seen plenty of developers fall into the subconscious trap of "I can't think of anything else to call this class, so I'll name it 'WidgetContext.'" Do you all agree that before naming our class a "Context," we may want to first consider some more descriptive terms? "Environment", "Configuraton", and "ExecutionState" come readily to mind.

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• How expensive is a context switch? Is it better to implement a manual task switch than to rely on OS

  - by Vilx-

  The title says it all. Imagine I have two (three, four, whatever) tasks that have to run in parallel. Now, the easy way to do this would be to create separate threads and forget about it. But on a plain old single-core CPU that would mean a lot of context switching - and we all know that context switching is big, bad, slow, and generally simply Evil. It should be avoided, right? On that note, if I'm writing the software from ground up anyway, I could go the extra mile and implement my own task-switching. Split each task in parts, save the state inbetween, and then switch among them within a single thread. Or, if I detect that there are multiple CPU cores, I could just give each task to a separate thread and all would be well. The second solution does have the advantage of adapting to the number of available CPU cores, but will the manual task-switch really be faster than the one in the OS core? Especially if I'm trying to make the whole thing generic with a TaskManager and an ITask, etc?

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• Cordova polluted logs with persistent.js add()

  - by slaver113

  I am using the latest phonegap/cordova version 2.1. and my log in Eclipse logcat get polluted with code when i do var allItems = Item.all(); allItems.list(null, function (results) { results.forEach(function (r) { console.log(r.id+ " " + r.lat + " " + r.long + " " + r.state); }); }); I get a output like (for 100s of lines) 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } at :1149822901

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• Best practice- How to team-split a django project while still allowing code reusal

  - by Infinity

  I know this sounds kind of vague, but please let me explain- I'm starting work on a brand new project, it will have two main components: "ACME PRODUCT" (think Gmail, Meebo, etc), and "THE SITE" (help, information, marketing stuff, promotional landing pages, etc lots of marketing-induced cruft). So basically the url /acme/* will load stuff in the uber cool ajaxy application, and every other URI will load stuff in the other site. Problem: "THE SITE" component is out of my hands, and will be handled by a consultants team that will work closely with marketing, And I and my team will work solely on the ACME PRODUCT. Question: How to set up the django project in such a way that we can have: Seperate releases. (They can push new marketing pages and functionality without having to worry about the state of our code. Maybe even separate Subversion "projects") Minimize impact (on our product) of whatever flying-unicorns-hocus-pocus the other team codes into the site. Still allow some code reusal. My main concern is that the ACME product needs to be rock solid, and therefore needs to be somewhat isolated of whatever mistakes/code bloopers the consultants make in their marketing side of the site. How have you handled this? Any ideas? Thanks!

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• iphone viewWillAppear not firing

  - by chzk

  I've read numerous posts about people having problems with viewWillAppear when you do not create your view heirarchy JUST right. My problem is I can't figure out what that means. If I create a RootViewController and call addSubView on that controller, I would expect the added view(s) to be wired up for viewWillAppear events. Does anyone have an example of a complex programmatic view heirarchy that successfully recieves viewWillAppear events at every level? Apple Docs state: Warning: If the view belonging to a view controller is added to a view hierarchy directly, the view controller will not receive this message. If you insert or add a view to the view hierarchy, and it has a view controller, you should send the associated view controller this message directly. Failing to send the view controller this message will prevent any associated animation from being displayed. The problem is that they don't describe how to do this. What the hell does "directly" mean. How do you "indirectly" add a view. I am fairly new to Cocoa and iPhone so it would be nice if there were useful examples from Apple besides the basic Hello World crap. Any help is greatly appreciated...

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• Sending custom app logs to developer

  - by Templar

  I'm planning to release a new app in the future. I have a custom logging function which logs some application data (not crashes) into a file (location manager state, app foreground-background transitions, main actions...). These logs helped me a lot to debug problems which were app-related, but not causing a crash. Until now these were in the documents directory (shared in iTunes) and the testers sent them to me after they saw some incorrect behaviors, however I don't want to share them anymore because this directory contains the app's database too. I'd like to obtain these logs even when the app will be on App Store, but I don't know how this should be done. As I wrote, it is a new app and even after the test phase may exist minor bugs. I know that the users can report problems in iTunes or on the Dev site, but without a detailed scenario or log it is really hard to correct a bug. Should I make some kind of in-app bug report functionality (even if this creates a wrong user impression) ? How is this usually handled ? Thanks

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• design pattern for related inputs

  - by curiousMo

  My question is a design question : let's say i have a data entry web page with 4 drop down lists, each depending on the previous one, and a bunch of text boxes. ddlCountry (DropDownList) ddlState (DropDownList) ddlCity (DropDownList) ddlBoro (DropDownList) txtAddress (TxtBox) txtZipcode(TxtBox) and an object that represents a datarow with a value for each: countrySeqid stateSeqid citySeqid boroSeqid address zipCode naturally the country, state, city and boro values will be values of primary keys of some lookup tables. when the user chooses to edits that record, i would load it from database and load it into the page. the issue that I have is how to streamline loading the DropDownLists. i have some code that would grab the object,look thru its values and move them to their corresponding input controls in one shot. but in this case i will have to load the ddlCountry with possible values, then assign values, then do the same thing for the rest of the ddls. I guess i am looking for an elegant solution. i am using asp.net, but i think it is irrelevant to the question. i am looking more into a design pattern.

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• Chicken and egg problem (restore database) when trying to write unit test against SQl Server 2008.

  - by Hamish Grubijan

  Ok, they are not unit tests but end-to-end tests. The setup is somewhat involved. Unit tests will use C#, ODBC connection. Every unit tests will try to clean up after itself, but every 20 tests or so (once per C# class) we would need to do a full database restore. I do not think I can do it over an ODBC connection, according to this document: http://www.sql-server-performance.com/articles/dba/Obtain_Exclusive_Access_to_Restore_SQL_Server_p1.aspx Msg 6104, Level 16, State 1, Line 1 Cannot use KILL to kill your own process. However, I would like to, so that 199 tests do not go amok because of a bad clean-up. Is there another way? Perhaps I can open a different "connection" such as use COM automation or something of that sort, and then kill all database connections from there? If so, how can I do that? Also, will the clients be able to re-connect automatically after a restore, or would I have to dismantle everything once every 20 tests or so? If you find this question confusing, please let me know what your questions are. Thanks!

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• Is encrypting session id (or other authenticate value) in cookie useful at all?

  - by Ji

  In web development, when session state is enabled, a session id is stored in cookie(in cookieless mode, query string will be used instead). In asp.net, the session id is encrypted automatically. There are plenty of topics on the internet regarding how you should encrypt your cookie, including session id. I can understand why you want to encrypt private info such as DOB, but any private info should not be stored in cookie at first place. So for other cookie values such as session id, what is the purpose encryption? Does it add security at all? no matter how you secure it, it will be sent back to server for decryption. Be be more specific, For authentication purpose, turn off session, i don't want to deal with session time out any more store some sort of id value in the cookie, on the server side, check if the id value exists and matches, if it is, authenticate user. let the cookie value expire when browser session is ended, this way. vs Asp.net form authentication mechanism (it relies on session or session id, i think) does latter one offer better security?

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• Parallel doseq for Clojure

  - by andrew cooke

  I haven't used multithreading in Clojure at all so am unsure where to start. I have a doseq whose body can run in parallel. What I'd like is for there always to be 3 threads running (leaving 1 core free) that evaluate the body in parallel until the range is exhausted. There's no shared state, nothing complicated - the equivalent of Python's multiprocessing would be just fine. So something like: (dopar 3 [i (range 100)] ; repeated 100 times in 3 parallel threads... ...) Where should I start looking? Is there a command for this? A standard package? A good reference? So far I have found pmap, and could use that (how do I restrict to 3 at a time? looks like it uses 32 at a time - no, source says 2 + number of processors), but it seems like this is a basic primitive that should already exist somewhere. clarification: I really would like to control the number of threads. I have processes that are long-running and use a fair amount of memory, so creating a large number and hoping things work out OK isn't a good approach (example which uses a significant chunk available mem). update: Starting to write a macro that does this, and I need a semaphore (or a mutex, or an atom i can wait on). Do semaphores exist in Clojure? Or should I use a ThreadPoolExecutor? It seems odd to have to pull so much in from Java - I thought parallel programming in Clojure was supposed to be easy... Maybe I am thinking about this completely the wrong way? Hmmm. Agents?

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• Deserialization of a DataSet... deal with column name changes? how to migrate data from one column to another?

  - by Brian Kennedy

  So, we wanted to slightly generalize a couple columns in our typed dataset... basically dropped a foreign key constraint and then wanted to change a couple column names to better reflect their new state. All that is easy. The problem is that our users may have serialized out the old version of the DataSet as XML. We want to be able to read those old XML files and deserialize them into the revised DataSet. It seems that would be a fairly common desire... but I haven't yet figured out the right thing to search the internet for. One possible solution would seem to be some way to give a DataColumn an alias or alternate name such that when it reads the old column name, it knows that data can be read into the column with the new column name. I can find no support for any such thing. Another approach would seem to be an "after deserialization" method of some sort... so, I would let it read in the old column values into a normal DataColumn with that name, and then in the "after deserialization" method I would just move the data from the obsolete column into the new column, and then delete the old columns. That would seem to generalize to many other situations... and having such events or hooks is pretty common in ADO.NET. But I have looked for such a hook and haven't yet found it. If no "after deserialization" hook, it would seem I ought to be able to override ReadXml or ReadXmlSerializable methods to call the base and then do my "after" stuff to fix up old data into new. But it does not appear that is possible. Soooo, I have to think backward compatibility with old serialized DataSets and simple data migration would be a well-solved problem... so, trying to reinvent that wheel seems silly. But so far, I haven't seemed to find any documentation on doing those things. Suggestions? What is best practice for this?

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• Can knowing C actually hurt the code you write in higher level languages?

  - by Jurily

  The question seems settled, beaten to death even. Smart people have said smart things on the subject. To be a really good programmer, you need to know C. Or do you? I was enlightened twice this week. The first one made me realize that my assumptions don't go further than my knowledge behind them, and given the complexity of software running on my machine, that's almost non-existent. But what really drove it home was this Slashdot comment: The end result is that I notice the many naive ways in which traditional C "bare metal" programmers assume that higher level languages are implemented. They make bad "optimization" decisions in projects they influence, because they have no idea how a compiler works or how different a good runtime system may be from the naive macro-assembler model they understand. Then it hit me: C is just one more abstraction, like all others. Even the CPU itself is only an abstraction! I've just never seen it break, because I don't have the tools to measure it. I'm confused. Has my mind been mutilated beyond recovery, like Dijkstra said about BASIC? Am I living in a constant state of premature optimization? Is there hope for me, now that I realized I know nothing about anything? Is there anything to know, even? And why is it so fascinating, that everything I've written in the last five years might have been fundamentally wrong? To sum it up: is there any value in knowing more than the API docs tell me? EDIT: Made CW. Of course this also means now you must post examples of the interpreter/runtime optimizing better than we do :)

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• Cross-platform HTML application options

  - by Charles

  I'd like to develop a stand-alone desktop application targeting Windows (XP through 7) and Mac (Tiger through Snow Leopard), and if possible iPhone and Android. In order to make it all work with as much common code as possible (and because it's the only thing I'm good at), I'd like to handle the main logic with HTML and JS. Using Adobe AIR is a possibility. And I think I can do this with various application wrappers, using .NET for Windows XP, Objective C for iPhone, Java for Android and native "widget" platform support for Mac and Windows Vista & 7 (though I'd like to keep the widget in the foreground, so the Mac dashboard isn't ideal). Does anyone have any suggestions on where to start? The two sticking points are: I'll certainly need some form of persistent storage (cookies perhaps) to keep state between sessions I'll also probably need access to remote data files, so if I use AJAX and the hosting HTML file resides on the device, it will need to be able to do cross-domain requests. I've done this on the iPhone without any problems, but I'd be surprised if this were possible on other platforms. For me, Android and iPhone will be the easiest to handle, and it looks like I can use Adobe AIR to handle the rest. But I wanted to know if there are any other alternatives. Does anyone have any suggesions?

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