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• Repeating fields in similar database tables

  - by user1738833

  I have been tasked with working on a database that I have never seen before and I'm looking at the DB structure. Some of the central and most heavily queried and joined tables look like virtual duplicates of each other. Here's a massively simplified representation of the situation, with business-sensitive information changed, listing hypothetical table names and fields: TopLevelGroup: PK_TLGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubGroup: PK_SubGroupId, FK_ParentTopLevelGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubSubGroup: PK_SubSUbGroupId, FK_ParentSubGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK I haven't listed the types of the fields as I don't think it's particularly important to the situation. In addition, it's worth saying that rather than four repeated fields as in the example above, I'm looking at 86 repeated fields. For the most part, those fields genuinely do represent "facts" about the primary table entity, so it's not automatically wrong for that reason. In addition, the "groups" represented here have a property inheritance relationship. If DisplaysXOnBill is NULL in the SubSubGroup, it takes the value of DisplaysXOnBillfrom it's parent, the SubGroup, and so-on up to the TopLevelGroup. Further, the requirements will never require that the model extends beyond three levels, so there is no need for flexibility in that area. Is there a design smell from several tables which describe very similar entities having almost identical fields? If so, what might be a better design of the example above? I'm using the phrase "design smell" to indicate a possible problem. Of course, in any given situation, a particular design might well be the best solution. I'm looking for a more general answer - wondering what might be wrong with this design and what might be the better design were that the case. Possibly related, but not primary questions: Is this database schema in a reasonably normal form (e.g. to 3NF), insofar as can be told from the information I've provided. I can't see a problem with the requirements of 2NF and 3NF, except in their inheriting the requirements of 1NF. Is 1NF satisfied though? Are repeating groups allowed in different tables? Is there a best-practice method for implementing the inheritance relationship in a database as I require? The method above feels clunky to me because any query on the SubSubGroup necessarily needs to join onto the SubGroup and the TopLevelGroup tables to collect inherited facts, which can make even trivial joins requiring facts from the SubSubGroup table rather long-winded. There are, of course, political considerations to making a relatively large change like this. For the purpose of this question, I'm happy to ignore that fact in the interests of keeping the answers ring-fenced to the technical problem.

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• keyDown works but i get beeps

  - by Oscar

  I just got my keydown method to work. But i get system beep everytime i press key. i have no idea whats wrong. Googled for hours and all people say is that if you have your keyDown method you should also implement the acceptsFirstResponder. did that to and it still doesn't work. #import <Cocoa/Cocoa.h> #import "PaddleView.h" #import "BallView.h" @interface GameController : NSView { PaddleView *leftPaddle; PaddleView *rightPaddle; BallView * ball; CGPoint ballVelocity; int gameState; int player1Score; int player2Score; } @property (retain) IBOutlet PaddleView *leftPaddle; @property (retain) IBOutlet PaddleView *rightPaddle; @property (retain) IBOutlet BallView *ball; - (void)reset:(BOOL)newGame; @end #import "GameController.h" #define GameStateRunning 1 #define GameStatePause 2 #define BallSpeedX 0.2 #define BallSpeedY 0.3 #define CompMoveSpeed 15 #define ScoreToWin 5 @implementation GameController @synthesize leftPaddle, rightPaddle, ball; - (id)initWithCoder:(NSCoder *)aDecoder { self = [super initWithCoder:aDecoder]; if(self) { gameState = GameStatePause; ballVelocity = CGPointMake(BallSpeedX, BallSpeedY); [NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES]; } return self; } - (void)gameLoop { if(gameState == GameStateRunning) { [ball setFrameOrigin:CGPointMake(ball.frame.origin.x + ballVelocity.x, ball.frame.origin.y + ballVelocity.y)]; if(ball.frame.origin.x + 15 > self.frame.size.width || ball.frame.origin.x < 0) { ballVelocity.x =- ballVelocity.x; } if(ball.frame.origin.y + 35 > self.frame.size.height || ball.frame.origin.y < 0) { ballVelocity.y =- ballVelocity.y; } } if(CGRectIntersectsRect(ball.frame, leftPaddle.frame)) { if(ball.frame.origin.x > leftPaddle.frame.origin.x) { ballVelocity.x =- ballVelocity.x; } } if(CGRectIntersectsRect(ball.frame, rightPaddle.frame)) { if(ball.frame.origin.x +15 > rightPaddle.frame.origin.x) { ballVelocity.x =- ballVelocity.x; } } if(ball.frame.origin.x <= self.frame.size.width / 2) { if(ball.frame.origin.y < leftPaddle.frame.origin.y + 75 && leftPaddle.frame.origin.y > 0) { [leftPaddle setFrameOrigin:CGPointMake(leftPaddle.frame.origin.x, leftPaddle.frame.origin.y - CompMoveSpeed)]; } if(ball.frame.origin.y > leftPaddle.frame.origin.y +75 && leftPaddle.frame.origin.y < 700 - leftPaddle.frame.size.height ) { [leftPaddle setFrameOrigin:CGPointMake(leftPaddle.frame.origin.x, leftPaddle.frame.origin.y + CompMoveSpeed)]; } } if(ball.frame.origin.x <= 0) { player2Score++; [self reset:(player2Score >= ScoreToWin)]; } if(ball.frame.origin.x + 15 > self.frame.size.width) { player1Score++; [self reset:(player1Score >= ScoreToWin)]; } } - (void)reset:(BOOL)newGame { gameState = GameStatePause; [ball setFrameOrigin:CGPointMake((self.frame.size.width + 7.5) / 2, (self.frame.size.height + 7.5)/2)]; if(newGame) { if(player1Score > player2Score) { NSLog(@"Player 1 Wins!"); } else { NSLog(@"Player 2 Wins!"); } player1Score = 0; player2Score = 0; } else { NSLog(@"Press key to serve"); } NSLog(@"Player 1: %d",player1Score); NSLog(@"Player 2: %d",player2Score); } - (void)moveRightPaddleUp { if(rightPaddle.frame.origin.y < 700 - rightPaddle.frame.size.height) { [rightPaddle setFrameOrigin:CGPointMake(rightPaddle.frame.origin.x, rightPaddle.frame.origin.y + 20)]; } } - (void)moveRightPaddleDown { if(rightPaddle.frame.origin.y > 0) { [rightPaddle setFrameOrigin:CGPointMake(rightPaddle.frame.origin.x, rightPaddle.frame.origin.y - 20)]; } } - (BOOL)acceptsFirstResponder { return YES; } - (void)keyDown:(NSEvent *)theEvent { if ([theEvent modifierFlags] & NSNumericPadKeyMask) { NSString *theArrow = [theEvent charactersIgnoringModifiers]; unichar keyChar = 0; if ( [theArrow length] == 0 ) { return; // reject dead keys } if ( [theArrow length] == 1 ) { keyChar = [theArrow characterAtIndex:0]; if ( keyChar == NSLeftArrowFunctionKey ) { gameState = GameStateRunning; } if ( keyChar == NSRightArrowFunctionKey ) { } if ( keyChar == NSUpArrowFunctionKey ) { [self moveRightPaddleUp]; } if ( keyChar == NSDownArrowFunctionKey ) { [self moveRightPaddleDown]; } [super keyDown:theEvent]; } } else { [super keyDown:theEvent]; } } - (void)drawRect:(NSRect)dirtyRect { } - (void)dealloc { [ball release]; [rightPaddle release]; [leftPaddle release]; [super dealloc]; } @end

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• My style/control template out my calendar's blackout dates.

  - by Chris

  Howdy, My C#/WPF project needs a calendar. We're going to be using it to pick a range of dates for appointment scheduling. I'm told the default calendar is too small to be used by some of our reps so I've been working on resizing it. <toolkit:Calendar Grid.Row="1" x:Name="DateWindowCalendar" BorderBrush="White" BorderThickness="0" Style="{StaticResource PopupCalendarStyle}" DisplayMode="Month" SelectionMode="SingleRange" DisplayDateStart="{Binding FirstDayOfMonth}" AutomationProperties.AutomationId="ToolkitCalendarId" VerticalAlignment="Top"> </toolkit:Calendar> And I've created this styling: <Style x:Key="PopupCalendarStyle" TargetType="toolkit:Calendar"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="toolkit:Calendar"> <StackPanel Margin="0" HorizontalAlignment="Center" x:Name="Root"> <toolkit:Calendar x:Name="Calendar" SelectedDate="{TemplateBinding SelectedDate}" DisplayDateStart="{TemplateBinding DisplayDateStart}" SelectionMode="{TemplateBinding SelectionMode}" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" SelectedDatesChanged="Calendar_SelectedDatesChanged"> <toolkit:Calendar.CalendarDayButtonStyle> <Style> <Setter Property="Button.Height" Value="34"/> <Setter Property="Button.Width" Value="34" /> <Setter Property="Button.FontSize" Value="16" /> </Style> </toolkit:Calendar.CalendarDayButtonStyle> <toolkit:Calendar.CalendarButtonStyle> <Style> <Setter Property="Button.Height" Value="34"/> <Setter Property="Button.Width" Value="34"/> <Setter Property="Button.FontSize" Value="16"/> </Style> </toolkit:Calendar.CalendarButtonStyle> </toolkit:Calendar> </StackPanel> </ControlTemplate> </Setter.Value> </Setter> </Style> Everything is almost perfect. I specify my range, I can track the selected dates (granted using the SelectedDatesChanged event instead of the SelectedDates property. The problem is I also need to be able to set blackout dates (usually the period between first of the month and today although sometimes first of the month to a few days from now). Without the styling, this works: DateWindowCalendar.BlackoutDates.Add(new CalendarDateRange( new DateTime(DateTime.Now.Year, DateTime.Now.Month, 01), DateTime.Now)); But when I add the style, I don't get the black out displays being displayed and worse its possible to select the blackout dates. I'm not sure what I missed but I'm hoping someone has an easy answer so that I don't have to rebuild the entire widget. Any help is appreciated. Thanks, Chris

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• Problem in finalizing the link list in C#

  - by Yasin

  My code was almost finished that a maddening bug came up! when i nullify the last node to finalize the link list , it actually dumps all the links and make the first node link Null ! when i trace it , its working totally fine creating the list in the loop but after the loop is done that happens and it destroys the rest of the link by doing so, and i don't understand why something so obvious is becoming problematic! (last line) struct poly { public int coef; public int pow; public poly* link;} ; poly* start ; poly* start2; poly* p; poly* second; poly* result; poly* ptr; poly* start3; poly* q; poly* q2; private void button1_Click(object sender, EventArgs e) { string holder = ""; IntPtr newP = Marshal.AllocHGlobal(sizeof(poly)); q = (poly*)newP.ToPointer(); start = q; int i = 0; while (this.textBox1.Text[i] != ',') { holder += this.textBox1.Text[i]; i++; } q->coef = int.Parse(holder); i++; holder = ""; while (this.textBox1.Text[i] != ';') { holder += this.textBox1.Text[i]; i++; } q->pow = int.Parse(holder); holder = ""; p = start; //creation of the first node finished! i++; for (; i < this.textBox1.Text.Length; i++) { newP = Marshal.AllocHGlobal(sizeof(poly)); poly* test = (poly*)newP.ToPointer(); while (this.textBox1.Text[i] != ',') { holder += this.textBox1.Text[i]; i++; } test->coef = int.Parse(holder); holder = ""; i++; while (this.textBox1.Text[i] != ';' && i < this.textBox1.Text.Length - 1) { holder += this.textBox1.Text[i]; if (i < this.textBox1.Text.Length - 1) i++; } test->pow = int.Parse(holder); holder = ""; p->link = test; //the addresses are correct and the list is complete } p->link = null; //only the first node exists now with a null link! }

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• Dynamic Objects for ASPxGridview

  - by André Snede Hansen

  I have a dictionary that is populated with data from a table, we are doing this so we can hold multiple SQL tables inside this object. This approached cannot be discussed. The Dictionary is mapped as a , and contains SQL column name and the value, and each dictionary resembles one row entry in the Table. Now I need to display this on a editable gridview, preferably the ASPxGridView. I already figured out that I should use Dynamic Objects(C#), and everything worked perfectly, up to the part where I find out that the ASPxGridview is built in .NET 2.0 and not 4.0 where Dynamic objects where implemented, therefor I cannot use it... As you cannot, to my knowledge, add rows to the gridview programmatically, I am out of ideas, and seek your help guys! protected void Page_Load(object sender, EventArgs e) { UserValidationTableDataProvider uvtDataprovider = _DALFactory.getProvider<UserValidationTableDataProvider>(typeof(UserValidationTableEntry)); string[] tableNames = uvtDataprovider.TableNames; UserValidationTableEntry[] entries = uvtDataprovider.getAllrecordsFromTable(tableNames[0]); userValidtionTableGridView.Columns.Clear(); Dictionary<string, string> firstEntry = entries[0].Values; foreach (KeyValuePair<string, string> kvp in firstEntry) { userValidtionTableGridView.Columns.Add(new GridViewDataColumn(kvp.Key)); } var dynamicObjectList = new List<dynamic>(); foreach (UserValidationTableEntry uvt in entries) { //dynamic dynObject = new MyDynamicObject(uvt.Values); dynamicObjectList.Add(new MyDynamicObject(uvt.Values)); } } public class MyDynamicObject : DynamicObject { Dictionary<string, string> properties = new Dictionary<string, string>(); public MyDynamicObject(Dictionary<string, string> dictio) { properties = dictio; } // If you try to get a value of a property // not defined in the class, this method is called. public override bool TryGetMember(GetMemberBinder binder, out object result) { // Converting the property name to lowercase // so that property names become case-insensitive. string name = binder.Name.ToLower(); string RResult; // If the property name is found in a dictionary, // set the result parameter to the property value and return true. // Otherwise, return false. bool wasSuccesfull = properties.TryGetValue(name, out RResult); result = RResult; return wasSuccesfull; } // If you try to set a value of a property that is // not defined in the class, this method is called. public override bool TrySetMember(SetMemberBinder binder, object value) { // Converting the property name to lowercase // so that property names become case-insensitive. properties[binder.Name.ToLower()] = value.ToString(); // You can always add a value to a dictionary, // so this method always returns true. return true; } } Now, I am almost certain that his "Dynamic object" approach, is not the one I can go with from here on. I hope you guys can help me :)!

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• Importing a large delimited file to a MySQL table

  - by Tom

  I have this large (and oddly formatted txt file) from the USDA's website. It is the NUT_DATA.txt file. But the problem is that it is almost 27mb! I was successful in importing the a few other smaller files, but my method was using file_get_contents which it makes sense why an error would be thrown if I try to snag 27+ mb of RAM. So how can I import this massive file to my MySQL DB without running into a timeout and RAM issue? I've tried just getting one line at a time from the file, but this ran into timeout issue. Using PHP 5.2.0. Here is the old script (the fields in the DB are just numbers because I could not figure out what number represented what nutrient, I found this data very poorly document. Sorry about the ugliness of the code): <? $file = "NUT_DATA.txt"; $data = split("\n", file_get_contents($file)); // split each line $link = mysql_connect("localhost", "username", "password"); mysql_select_db("database", $link); for($i = 0, $e = sizeof($data); $i < $e; $i++) { $sql = "INSERT INTO `USDA` (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17) VALUES("; $row = split("\^", trim($data[$i])); // split each line by carrot for ($j = 0, $k = sizeof($row); $j < $k; $j++) { $val = trim($row[$j], '~'); $val = (empty($val)) ? 0 : $val; $sql .= ((empty($val)) ? 0 : $val) . ','; // this gets rid of those tildas and replaces empty strings with 0s } $sql = rtrim($sql, ',') . ");"; mysql_query($sql) or die(mysql_error()); // query the db } echo "Finished inserting data into database.\n"; mysql_close($link); ?>

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• How do you use technology to memorize set of terms?

  - by user49767

  Always there are few set of items needs to be memorized in short span of time. Here are my following cases. 1) My Job requires some set of items needs to be memorized. 2) I am a developer who has to learn 150+ tags within next 3 days. 3) Fix developer/support has to remember minimum of 125+ tags (set of possible values). 4) It is better if team's SQL developer knows all the table and columns in my database. 5) When guys join new department or job. Memorizing few related items will definitely gives some benefit. Most of the cases, I suggest people to understand the domain better and nothing wrong in using google (but remember correct search-word). But recently I came across a junior developer who took lot of effort in memorizing set of things (150+ table structures, fix protocol tags, almost 300+ configuration items from property file) and was very very successful in his job and was swift in responding for support queries. Needless to say he is smart worker too (not a dumb guy). When I try to recollect some of the successful employees I met, they were so good in remembering entire schema and they did in short span of time. But I don't argue that memorizing alone gives success, but it greatly helps when situation demands. Here my question is, I am not good at remembering things, but it shouldn't be lame excuse. Hence I am evaluating using technolgies better to memorize set of items. Not very much interested in memory techniques (mnemoninc, photography memory, etc..). Even I have recorded 100+ items and listen to that whenever I found free time, defintely there were some fruitful result. Now I need your suggestion about what are all the ways to exploit technology to memorize. There could be so many reason why guys remember a subject (passionate, essential, author, creator, responsbile). Not interested in dissecting why guys remeber. Rather much interested in using ways, and techniques (cheat sheet...) to remember a set of itmes. Note : I appreciate, encourage people who could rephrase my question better. Note : I have kept couple of cheat-sheet close to my monitor, honestly it did not help me :).

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• Cpp some basic problems

  - by DevAno1

  Hello. My task was as follows : Create class Person with char*name and int age. Implement contructor using dynamic allocation of memory for variables, destructor, function init and friend function show. Then transform this class to header and cpp file and implement in other program. Ok so I've almost finished my Person class, but I get error after destructor. First question is how to write this properly ? #include <iostream> using namespace std; class Person { char* name; int age; public: int * take_age(); Person(){ int size=0; cout << "Give length of char*" << endl; cin >> size; name = new char[size]; age = 0; } ~Person(){ cout << "Destroying resources" << endl; delete *[] name; delete * take_age(); } friend void(Person &p); int * Person::take_age(){ return age; } void init(char* n, int a) { name = n; age = a; } void show(Person &p){ cout << "Name: " << p.name << "," << "age: " << p.age << endl; } }; int main(void) { Person *p = new Person; p->init("Mary", 25); p.show(); system("PAUSE"); return 0; } And now with header/implementation part : - do I need to introduce constructor in header/implementation files ? If yes - how? - my show() function is a friendly function. Should I take it into account somehow ? I already failed to return this task on my exam, but still I'd like to know how to implement it.

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• Netsuite - how to specify record_type for getall request

  - by Dvporg

  I want to get a list of all InventoryItems According to this document: https://system.netsuite.com/help/helpcenter/en_US/Output/Help/SuiteCloudCustomizationScriptingWebServices/SuiteTalkWebServices/getAll.html I'm forming the following request: <env:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:platformMsgs="urn:platform_2013_1.webservices.netsuite.com" xmlns:env="http://schemas.xmlsoap.org/soap/envelope/"> <env:Header> <passport> <email>******</email> <password>******</password> <account>******</account> </passport> </env:Header> <env:Body> <platformMsgs:getAll> <recordType>InventoryItem</recordType> </platformMsgs:getAll> </env:Body> </env:Envelope> But receiving response with the error: <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <soapenv:Header> <platformMsgs:documentInfo xmlns:platformMsgs="urn:messages_2013_1.platform.webservices.netsuite.com"> <platformMsgs:nsId>WEBSERVICES_969904_100920131651936419141601801_cbf1690968b43</platformMsgs:nsId> </platformMsgs:documentInfo> </soapenv:Header> <soapenv:Body> <getAllResponse xmlns="urn:platform_2013_1.webservices.netsuite.com"> <platformCore:getAllResult xmlns:platformCore="urn:core_2013_1.platform.webservices.netsuite.com"> <platformCore:status isSuccess="false"> <platformCore:statusDetail type="ERROR"> <platformCore:code>GETALL_RCRD_TYPE_REQD</platformCore:code> <platformCore:message>The getAll record type is required.</platformCore:message> </platformCore:statusDetail> </platformCore:status> </platformCore:getAllResult> </getAllResponse> </soapenv:Body> </soapenv:Envelope> I've tried to request currencies, states - the response always the same I've tried following variants: <GetAllRecordType>inventoryItem</GetAllRecordType> and <recordType>inventoryItem</recordType> and <GetAllRecordType>currency</GetAllRecordType> and <recordType>currency</recordType> with the same response: <platformCore:message>The getAll record type is required.</platformCore:message> According to https://webservices.netsuite.com/xsd/platform/v2013_2_0/coreTypes.xsd - I've specified correctly recordType (btw I've also tried without any success) I'm using ruby and there is no complete library for ruby. The one that is exists doesn't contain almost all things I'm going to use. Can someone help me what I'm doing wrong or may be someone have working example

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• J2ME/Java: Referencing StringBuffer through Threads

  - by Jemuel Dalino

  This question might be long, but I want to provide much information. Overview: I'm creating a Stock Quotes Ticker app for Blackberry. But I'm having problems with my StringBuffer that contains an individual Stock information. Process: My app connects to our server via SocketConnection. The server sends out a formatted set of strings that contains the latest Stock trade. So whenever a new trade happens, the server will send out an individual Stock Quote of that trade. Through an InputStream I am able to read that information and place each character in a StringBuffer that is referenced by Threads. By parsing based on char3 I am able to determine a set of stock quote/information. char1 - to separate data char3 - means end of a stock quote/information sample stock quote format sent out by our server: stock_quote_name(char 1)some_data(char1)some_data(char1)(char3) My app then parses that stock quote to compare certain data and formats it how it will look like when displayed in the screen. When trades happen gradually(slow) the app works perfectly. However.. Problem: When trades happen too quickly and almost at the same time, My app is not able to handle the information sent efficiently. The StringBuffer has its contents combined with the next trade. Meaning Two stock information in one StringBuffer. field should be: Stock_quote_name some_data some_data sample of what's happening: Stock_quote_name some_data some_dataStock_quote_name some_data some_data here's my code for this part: while (-1 != (data = is.read())) { sb.append((char)data); while(3 != (data = is.read())) { sb.append((char)data); } UiApplication.getUiApplication().invokeLater(new Runnable() { public void run() { try { synchronized(UiApplication.getEventLock()) { SetStringBuffer(sb); DisplayStringBuffer(); RefreshStringBuffer(); } } catch (Exception e) { System.out.println("Error in setting stringbuffer: " + e.toString()); } } }); } public synchronized void DisplayStringBuffer() { try { //parse sb - string buffer ...... } catch(Exception ex) { System.out.println("error in DisplayStringBuffer(): " + ex.toString()); } } public synchronized void SetStringBuffer(StringBuffer dataBuffer) { this.sb =dataBuffer; System.out.println(sb); } public synchronized void RefreshStringBuffer() { this.sb.delete(0, this.sb.length()); } From what I can see, when trades happen very fast, The StringBuffer is not refreshed immediately and still has the contents of the previous trade, when i try to put new data. My Question is: Do you guys have any suggestion on how i can put data into the StringBuffer, without the next information being appended to the first content

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• Optimizing tasks to reduce CPU in a trading application

  - by Joel

  Hello, I have designed a trading application that handles customers stocks investment portfolio. I am using two datastore kinds: Stocks - Contains unique stock name and its daily percent change. UserTransactions - Contains information regarding a specific purchase of a stock made by a user : the value of the purchase along with a reference to Stock for the current purchase. db.Model python modules: class Stocks (db.Model): stockname = db.StringProperty(multiline=True) dailyPercentChange=db.FloatProperty(default=1.0) class UserTransactions (db.Model): buyer = db.UserProperty() value=db.FloatProperty() stockref = db.ReferenceProperty(Stocks) Once an hour I need to update the database: update the daily percent change in Stocks and then update the value of all entities in UserTransactions that refer to that stock. The following python module iterates over all the stocks, update the dailyPercentChange property, and invoke a task to go over all UserTransactions entities which refer to the stock and update their value: Stocks.py # Iterate over all stocks in datastore for stock in Stocks.all(): # update daily percent change in datastore db.run_in_transaction(updateStockTxn, stock.key()) # create a task to update all user transactions entities referring to this stock taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock') }) def updateStockTxn(stock_key): #fetch the stock again - necessary to avoid concurrency updates stock = db.get(stock_key) stock.dailyPercentChange= data.get('some_val_for_stock') # I get this value from outside ... some more calculations here ... stock.put() Task.py (/task) # Amount of transaction per task amountPerCall=10 stock=db.get(self.request.get("stock_key")) # Get all user transactions which point to current stock user_transaction_query=stock.usertransactions_set cursor=self.request.get("cursor") if cursor: user_transaction_query.with_cursor(cursor) # Spawn another task if more than 10 transactions are in datastore transactions = user_transaction_query.fetch(amountPerCall) if len(transactions)==amountPerCall: taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock'), 'cursor': user_transaction_query.cursor() }) # Iterate over all transaction pointing to stock and update their value for transaction in transactions: db.run_in_transaction(updateUserTransactionTxn, transaction.key()) def updateUserTransactionTxn(transaction_key): #fetch the transaction again - necessary to avoid concurrency updates transaction = db.get(transaction_key) transaction.value= transaction.value* self.request.get ('some_val_for_stock') db.put(transaction) The problem: Currently the system works great, but the problem is that it is not scaling well… I have around 100 Stocks with 300 User Transactions, and I run the update every hour. In the dashboard, I see that the task.py takes around 65% of the CPU (Stock.py takes around 20%-30%) and I am using almost all of the 6.5 free CPU hours given to me by app engine. I have no problem to enable billing and pay for additional CPU, but the problem is the scaling of the system… Using 6.5 CPU hours for 100 stocks is very poor. I was wondering, given the requirements of the system as mentioned above, if there is a better and more efficient implementation (or just a small change that can help with the current implemntation) than the one presented here. Thanks!! Joel

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• deadlock when using WCF Duplex Polling with Silverlight

  - by Kobi Hari

  Hi all. I have followed Tomek Janczuk's demonstration on silverlight tv to create a chat program that uses WCF Duplex Polling web service. The client subscribes to the server, and then the server initiates notifications to all connected clients to publish events. The Idea is simple, on the client, there is a button that allows the client to connect. A text box where the client can write a message and publish it, and a bigger text box that presents all the notifications received from the server. I connected 3 clients (in different browsers - IE, Firefox and Chrome) and it all works nicely. They send messages and receive them smoothly. The problem starts when I close one of the browsers. As soon as one client is out, the other clients get stuck. They stop getting notifications. I am guessing that the loop in the server that goes through all the clients and sends them the notifications is stuck on the client that is now missing. I tried catching the exception and removing it from the clients list (see code) but it still does not help. any ideas? The server code is as follows: using System; using System.Linq; using System.Runtime.Serialization; using System.ServiceModel; using System.ServiceModel.Activation; using System.Collections.Generic; using System.Runtime.Remoting.Channels; namespace ChatDemo.Web { [ServiceContract] public interface IChatNotification { // this will be used as a callback method, therefore it must be one way [OperationContract(IsOneWay=true)] void Notify(string message); [OperationContract(IsOneWay = true)] void Subscribed(); } // define this as a callback contract - to allow push [ServiceContract(Namespace="", CallbackContract=typeof(IChatNotification))] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] public class ChatService { SynchronizedCollection<IChatNotification> clients = new SynchronizedCollection<IChatNotification>(); [OperationContract(IsOneWay=true)] public void Subscribe() { IChatNotification cli = OperationContext.Current.GetCallbackChannel<IChatNotification>(); this.clients.Add(cli); // inform the client it is now subscribed cli.Subscribed(); Publish("New Client Connected: " + cli.GetHashCode()); } [OperationContract(IsOneWay = true)] public void Publish(string message) { SynchronizedCollection<IChatNotification> toRemove = new SynchronizedCollection<IChatNotification>(); foreach (IChatNotification channel in this.clients) { try { channel.Notify(message); } catch { toRemove.Add(channel); } } // now remove all the dead channels foreach (IChatNotification chnl in toRemove) { this.clients.Remove(chnl); } } } } The client code is as follows: void client_NotifyReceived(object sender, ChatServiceProxy.NotifyReceivedEventArgs e) { this.Messages.Text += string.Format("{0}\n\n", e.Error != null ? e.Error.ToString() : e.message); } private void MyMessage_KeyDown(object sender, KeyEventArgs e) { if (e.Key == Key.Enter) { this.client.PublishAsync(this.MyMessage.Text); this.MyMessage.Text = ""; } } private void Button_Click(object sender, RoutedEventArgs e) { this.client = new ChatServiceProxy.ChatServiceClient(new PollingDuplexHttpBinding { DuplexMode = PollingDuplexMode.MultipleMessagesPerPoll }, new EndpointAddress("../ChatService.svc")); // listen for server events this.client.NotifyReceived += new EventHandler<ChatServiceProxy.NotifyReceivedEventArgs>(client_NotifyReceived); this.client.SubscribedReceived += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(client_SubscribedReceived); // subscribe for the server events this.client.SubscribeAsync(); } void client_SubscribedReceived(object sender, System.ComponentModel.AsyncCompletedEventArgs e) { try { Messages.Text += "Connected!\n\n"; gsConnect.Color = Colors.Green; } catch { Messages.Text += "Failed to Connect!\n\n"; } } And the web config is as follows: <system.serviceModel> <extensions> <bindingExtensions> <add name="pollingDuplex" type="System.ServiceModel.Configuration.PollingDuplexHttpBindingCollectionElement, System.ServiceModel.PollingDuplex, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/> </bindingExtensions> </extensions> <behaviors> <serviceBehaviors> <behavior name=""> <serviceMetadata httpGetEnabled="true"/> <serviceDebug includeExceptionDetailInFaults="false"/> </behavior> </serviceBehaviors> </behaviors> <bindings> <pollingDuplex> <binding name="myPollingDuplex" duplexMode="MultipleMessagesPerPoll"/> </pollingDuplex> </bindings> <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true"/> <services> <service name="ChatDemo.Web.ChatService"> <endpoint address="" binding="pollingDuplex" bindingConfiguration="myPollingDuplex" contract="ChatDemo.Web.ChatService"/> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/> </service> </services> </system.serviceModel>

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• log4net initialisation

  - by Ruben Bartelink

  I've looked hard for duplicates but have to ask the following, no matter how basic it may seem, to get it clear once and for all! In a fresh Console app using log4net version 1.2.10.0 on VS28KSP1 on 64 bit W7, I have the following code:- using log4net; using log4net.Config; namespace ConsoleApplication1 { class Program { static readonly ILog _log = LogManager.GetLogger(typeof(Program)); static void Main(string[] args) { _log.Info("Ran"); } } } In my app.config, I have: <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" /> </configSections> <log4net> <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender"> <file value="Program.log" /> <lockingModel type="log4net.Appender.FileAppender+MinimalLock" /> <appendToFile value="true" /> <rollingStyle value="Size" /> <maxSizeRollBackups value="10" /> <maximumFileSize value="1MB" /> <staticLogFileName value="true" /> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="[%username] %date [%thread] %-5level %logger [%property{NDC}] - %message%newline" /> </layout> </appender> <root> <level value="DEBUG" /> <appender-ref ref="RollingFileAppender" /> </root> </log4net> </configuration> This doesnt write anything, unless I either add an attribute: [ assembly:XmlConfigurator ] Or explicitly initialise it in Main(): _log.Info("This will not go to the log"); XmlConfigurator.Configure(); _log.Info("Ran"); This raises the following questions: I'm almost certain I've seen it working somewhere on some version of log4net without the addition of the assembly attribute or call in Main. Can someone assure me I'm not imagining that? Can someone please point me to where in the doc it explicitly states that both the config section and the initialisation hook are required - hopefully with an explanation of when this changed, if it did? I can easily imagine why this might be the policy -- having the initialisation step explicit to avoid surprises etc., it's just that I seem to recall this not always being the case... (And normally I have the config in a separate file, which generally takes configsections out of the picture)

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• SQLAlchemy unsupported type error - and table design issues?

  - by Az

  Hi there, back again with some more SQLAlchemy shenanigans. Let me step through this. My table is now set up as so: engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('sid', Integer, primary_key=True), Column('name', String), Column('preferences', Integer), Column('allocated_rank', Integer), Column('allocated_project', Integer) ) metadata.create_all(engine) mapper(Student, students_table) Fairly simple, and for the most part I've been enjoying the ability to query almost any bit of information I want provided I avoid the error cases below. The class it is mapped from is: class Student(object): def __init__(self, sid, name): self.sid = sid self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.sid, self.name) Explanation: preferences is basically a set of all the projects the student would prefer to be assigned. When the allocation algorithm kicks in, a student's allocated_project emerges from this preference set. Now if I try to do this: for student in students.itervalues(): session.add(student) session.commit() It throws two errors, one for the allocated_project column (seen below) and a similar error for the preferences column: sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 4 - probably unsupported type. u'INSERT INTO studs (sid, name, allocated_rank, allocated_project) VALUES (?, ?, ?, ?, ?, ?, ?)' [1101, 'Muffett,M.', 1, 888 Human-spider relationships (Supervisor id: 123)] If I go back into my code I find that, when I'm copying the preferences from the given text files, it actually refers to the Project class which is mapped to a dictionary, using the unique project id's (pid) as keys. Thus, as I iterate through each student via their rank and to the preferences set, it adds not a project id, but the reference to the project id from the projects dictionary. students[sid].preferences[int(rank)].add(projects[int(pid)]) Now this is very useful to me since I can find out all I want to about a student's preferred projects without having to run another check to pull up information about the project id. The form you see in the error has the object print information passed as: return "%s %s (Supervisor id: %s)" %(self.proj_id, self.proj_name, self.proj_sup) My questions are: I'm trying to store an object in a database field aren't I? Would the correct way then, be copying the project information (project id, name, etc) into its own table, referenced by the unique project id? That way I can just have the project id field for one of the student tables just be an integer id and when I need more information, just join the tables? So and so forth for other tables? If the above makes sense, then how does one maintain the relationship with a column of information in one table which is a key index on another table? Does this boil down into a database design problem? Are there any other elegant ways of accomplishing this? Apologies if this is a very long-winded question. It's rather crucial for me to solve this, so I've tried to explain as much as I can, whilst attempting to show that I'm trying (key word here sadly) to understand what could be going wrong.

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• Web reference problem on WCF

  - by kaivalya

  I have a WCF service which I am able to connect to from my web application and get data. I now added a web reference to this wcf project to a wsdl file that a shipping company provides. Intention is to get shipping quotes.. I am able to access the objects that are generated from this wsdl file but when I call service.Authenticate("DEMO"); method almost nothing happens. I debug and see the debugger continue to the next lines but there is no change on service parameters and service.isauthorized is null.. Can you lead me to how I should debug this further and things I should check, or if there are additional steps that I need to ensure to have a web reference working on wcf app Thanks using System; using System.Collections.Generic; using System.Linq; using System.Runtime.Serialization; using System.ServiceModel; using System.Text; using ShippingCalculator.com.freight.api; namespace ShippingCalculator { public class ShippingService : IShippingService { freight_service service = new freight_service(); public string GetData(int value) { service.setConnectionType(".net"); service.Authenticate("DEMO"); OriginRequest origin = new OriginRequest(); origin.zip = "60101"; DestinationRequest destination = new DestinationRequest(); destination.zip = "10001"; PackageRequest package = new PackageRequest(); package.weight = "10"; ShipmentInfoRequest shipmentInfo = new ShipmentInfoRequest(); shipmentInfo.ship_date = DateTime.Now.AddDays(5); service.setOrigin(origin); service.setDestination(destination); service.setPackage(package); service.setShipmentInfo(shipmentInfo); Quote quote = service.getQuote(); return string.Format("Quote Number: {0}<br /> ", quote.QuoteNumber); } } } using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using ShippingTestApp.ShippingServiceReference; namespace ShippingTestApp.Controllers { [HandleError] public class HomeController : Controller { public ActionResult Index() { ShippingServiceClient shipClient = new ShippingServiceClient(); shipClient.GetData(0); ViewData["Message"] = shipClient.GetData(0); return View(); } } }

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• SVN: Branches for Every Little Change?

  - by yar

  Hi. We have a client (who has a client, who has a client) who is driving us mad with change requests to a code base (in PHP). Our first response was to just work in a main trunk in SVN, but the client often comes back and requests that a certain change needs to get pushed to the live servers ASAP. On the other hand, other changes get reduced in priority suddenly, which originally came grouped with other changes (seemingly). We are thinking of using a branch for every change request. Is this mad? What other solutions might work? Thanks! Edit: This is a really hard question to choose the correct answer for. Thanks to everybody for your great answers. Edit: I know that the best answer I chose was not particularly popular. I too wanted to find a technical solution to this problem. But now I think that if the client wants software with features that can be deployed in a modular fashion... this problem should not be solved in our use of the version control system. It would have to be designed into the software. Edit: Now it's almost a month later and my coworker/client has convinced me that multiple branches is the way to go. This is not just due to the client's insanity, but also based on our need to be able to determine if a feature is "ready to go" or "needs more work" or whatever. I don't have the SVN with me, but we merge using the advice from the SVN Cookbook: you merge the branch from the revision it was branched to the head revision. Also, using this system, we merge all branches at some point and that becomes the new QA and then live build. Then we branch from that. Last Edit (Perhaps): Months later, this system is still working out for us. We create branches for every ticket and rarely have problems. On the other hand, we do try to keep things separate as far as what people are working on... Two Years Later: We use GIT now, and now this system is actually quite reasonable.

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• Optimize MySQL query (ngrams, COUNT(), GROUP BY, ORDER BY)

  - by Gerardo

  I have a database with thousands of companies and their locations. I have implemented n-grams to optimize search. I am making one query to retrieve all the companies that match with the search query and another one to get a list with their locations and the number of companies in each location. The query I am trying to optimize is the latter. Maybe the problem is this: Every company ('anunciante') has a field ('estado') to make logical deletes. So, if 'estado' equals 1, the company should be retrieved. When I run the EXPLAIN command, it shows that it goes through almost 40k rows, when the actual result (the reality matching companies) are 80. How can I optimize this? This is my query (XXX represent the n-grams for the search query): SELECT provincias.provincia AS provincia, provincias.id, COUNT(*) AS cantidad FROM anunciantes JOIN anunciante_invertido AS a_i0 ON anunciantes.id = a_i0.id_anunciante JOIN indice_invertido AS indice0 ON a_i0.id_invertido = indice0.id LEFT OUTER JOIN domicilios ON anunciantes.id = domicilios.id_anunciante LEFT OUTER JOIN localidades ON domicilios.id_localidad = localidades.id LEFT OUTER JOIN provincias ON provincias.id = localidades.id_provincia WHERE anunciantes.estado = 1 AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') AND indice0.id IN (SELECT invertido_ngrama.id_palabra FROM invertido_ngrama JOIN ngrama ON ngrama.id = invertido_ngrama.id_ngrama WHERE ngrama.ngrama = 'XXX') GROUP BY provincias.id ORDER BY cantidad DESC And this is the query explained (hope it can be read in this format): id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY anunciantes ref PRIMARY,estado estado 1 const 36669 Using index; Using temporary; Using filesort 1 PRIMARY domicilios ref id_anunciante id_anunciante 4 db84771_viaempresas.anunciantes.id 1 1 PRIMARY localidades eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.domicilios.id_localidad 1 1 PRIMARY provincias eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.localidades.id_provincia 1 1 PRIMARY a_i0 ref PRIMARY,id_anunciante,id_invertido PRIMARY 4 db84771_viaempresas.anunciantes.id 1 Using where; Using index 1 PRIMARY indice0 eq_ref PRIMARY PRIMARY 4 db84771_viaempresas.a_i0.id_invertido 1 Using index 6 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 6 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 5 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 5 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 4 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 4 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 3 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 3 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index 2 DEPENDENT SUBQUERY ngrama const PRIMARY,ngrama ngrama 5 const 1 Using index 2 DEPENDENT SUBQUERY invertido_ngrama eq_ref PRIMARY,id_palabra,id_ngrama PRIMARY 8 func,const 1 Using index

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• How do I create a Spring 3 + Tiles 2 webapp using REST-ful URLs?

  - by Ichiro Furusato

  I'm having a heck of a time resolving URLs with Spring 3.0 MVC. I'm just building a HelloWorld to try out how to build a RESTful webapp in Spring, nothing theoretically complicated. All of the examples I've been able to find are based on configurations that pay attention to file extensions ("*.htm" or "*.do"), include an artificial directory name prefix ("/foo") or even prefix paths with a dot (ugly), all approaches that use some artificial regex pattern as a signal to the resolver. For a REST approach I want to avoid all that muck and use only the natural URL patterns of my application. I would assume (perhaps incorrectly) that in web.xml I'd set a url-pattern of "/*" and pass everything to the DispatcherServlet for resolution, then just rely on URL patterns in my controller. I can't reliably get my resolver(s) to catch the URL patterns, and in all my trials this results in a resource not found error, a stack overflow (loop), or some kind of opaque Spring 3 ServletException stack trace — one of my ongoing frustrations with Spring generally is that the error messages are not often very helpful. I want to work with a Tiles 2 resolver. I've located my *.jsp files in WEB-INF/views/ and have a single line index.jsp file at the application root redirecting to the index file set by my layout.xml (the Tiles 2 Configurer). I do all the normal Spring 3 high-level configuration: <mvc:annotation-driven /> <mvc:view-controller path="/" view-name="index"/> <context:component-scan base-package="com.acme.web.controller" /> ...followed by all sorts of combinations and configurations of UrlBasedViewResolver, InternalResourceViewResolver, UrlFilenameViewController, etc. with all manner of variantions in my Tiles 2 configuration file. Then in my controller I've trying to pick up my URL patterns. Problem is, I can't reliably even get the resolver(s) to catch the patterns to send to my controller. This has now stretched to multiple days with no real progress on something I thought would be very simple to implement. I'm perhaps trying to do too much at once, though I would think this should be a simple (almost a default) configuration. I'm just trying to create a simple HelloWorld-type application, I wouldn't expect this is rocket science. Rather than me post my own configurations (which have ranged all over the map), does anyone know of an online example that: shows a simple Spring 3 MVC + Tiles 2 web application that uses REST-ful URLs (i.e., avoiding forced URL patterns such as file extensions, added directory names or dots) and relies solely on Spring 3 code/annotations (i.e., nothing outside of Spring MVC itself) to accomplish this? Is there an easy way to do this? Thanks very much for any help.

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• Is the recent trend toward widescreen (16:9) computer monitors a plus or minus for programmers?

  - by DanM

  It's almost gotten to the point where you can't buy a conventional (4:3) monitor anymore. Pretty much everything is widescreen. This is fine for watching movies or TV, but is it good or bad for programming? My initial thoughts on the issue are that widescreens are a net negative for programmers. Here are some of the disadvantages I see: Poor space utiliziation One disadvantage of widescreens you can't argue with is that they offer poor space utilization for the amount of total pixels you get. For example, my Thinkpad, which I bought just before the widescreen craze, has a 15" monitor with a native resolution of 1600 x 1200. The newer 15.4" Thinkpads run at most 1680 x 1050. So (if you do the math) you get fewer pixels in a wider (but not shorter) package. With desktop monitors, you pay a price in terms of desk space used. Two 1680 x 1050 monitors will simply take up more of your desk than two 1600 x 1200 monitors (assuming equal dot pitch). More scrolling If you compare a 1680 x 1050 monitor to a 1600 x 1200 monitor, you get 80 extra pixels of width but 150 fewer pixels of height. The height reduction means you lose approximately 11 lines of code. That's less you can see on the screen at one time and more scrolling you have to do. This harms productivity, maybe not dramatically, but insidiously. Less room for wide panels Widescreens also mean you lose space for wide but short panels common in programming environments. If you use Visual Studio, for example, your code window will be that much shorter when viewing the Find Results, Task List, or Error List (all of which I use frequently). This isn't to say the 80 pixels of extra width you get with widescreen would never be useful, but I tend to keep my lines of code short, so seeing more lines would be more valuable to me than seeing fewer, longer lines. What do you think? Do you agree/disagree? Are you now using one or more widescreen monitors for development? What resolution are you running on each? Do you ever miss the height of the traditional 4:3 monitor? Would you complain if your monitors were one inch narrower but two inches taller?

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• IP address numbers in MySQL subquery

  - by Iain Collins

  I have a problem with a subquery involving IPV4 addresses stored in MySQL (MySQL 5.0). The IP addresses are stored in two tables, both in network number format - e.g. the format output by MySQL's INET_ATON(). The first table ('events') contains lots of rows with IP addresses associated with them, the second table ('network_providers') contains a list of provider information for given netblocks. events table (~4,000,000 rows): event_id (int) event_name (varchar) ip_address (unsigned 4 byte int) network_providers table (~60,000 rows): ip_start (unsigned 4 byte int) ip_end (unsigned 4 byte int) provider_name (varchar) Simplified for the purposes of the problem I'm having, the goal is to create an export along the lines of: event_id,event_name,ip_address,provider_name If do a query along the lines of either of the following, I get the result I expect: SELECT provider_name FROM network_providers WHERE INET_ATON('192.168.0.1') >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 SELECT provider_name FROM network_providers WHERE 3232235521 >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 That is to say, it returns the correct provider_name for whatever IP I look up (of course I'm not really using 192.168.0.1 in my queries). However, when performing this same query as a subquery, in the following manner, it doesn't yield the result I would expect: SELECT event.id, event.event_name, (SELECT provider_name FROM network_providers WHERE event.ip_address >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1) as provider FROM events Instead the a different (incorrect) value for network_provider is returned - over 90% (but curiously not all) values returned in the provider column contain the wrong provider information for that IP. Using event.ip_address in a subquery just to echo out the value confirms it contains the value I'd expect and that the subquery can parse it. Replacing event.ip_address with an actual network number also works, just using it dynamically in the subquery in this manner that doesn't work for me. I suspect the problem is there is something fundamental and important about subqueries in MySQL that I don't get. I've worked with IP addresses like this in MySQL quite a bit before, but haven't previously done lookups for them using a subquery. The question: I'd really appreciate an example of how I could get the output I want, and if someone here knows, some enlightenment as to why what I'm doing doesn't work so I can avoid making this mistake again. Notes: The actual real-world usage I'm trying to do is considerably more complicated (involving joining two or three tables). This is a simplified version, to avoid overly complicating the question. Additionally, I know I'm not using a between on ip_start & ip_end - that's intentional (the DB's can be out of date, and such cases the owner in the DB is almost always in the next specified range and 'best guess' is fine in this context) however I'm grateful for any suggestions for improvement that relate to the question. Efficiency is always nice, but in this case absolutely not essential - any help appreciated.

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• Move options between multiple lists

  - by Martha

  We currently have a form with the standard multi-select functionality of "here are the available options, here are the selected options, here are some buttons to move stuff back and forth." However, the client now wants the ability to not just select certain items, but to also categorize them. For example, given a list of books, they want to not just select the ones they own, but also the ones they've read, the ones they would like to read, and the ones they've heard about. (All examples fictional.) Thankfully, a selected item can only be in one category at a time. I can find many examples of moving items between listboxes, but not a single one for moving items between multiple listboxes. To add to the complication, the form needs to have two sets of list+categories, e.g. a list of movies that need to be categorized in addition to the aforementioned books. EDIT: Having now actually sat down to try to code the non-javascripty bits, I need to revise my question, because I realized that multiple select lists won't really work from the "how do I inform the server about all this lovely new information" standpoint. So the html code is now a pseudo-listbox, i.e. an unordered list (ul) displayed in a box with a scrollbar, and each list item (<li>) has a set of five radio buttons (unselected/own/read/like/heard). My task is still roughly the same: how to take this one list and make it easy to categorize the items, in such a way that the user can tell at a glance what is in what category. (The pseudo-listbox has some of the same disadvantages as a multi-select listbox, namely it's hard to tell what's selected if the list is long enough to scroll.) The dream solution would be a drag-and-drop type thing, but at this point even buttons would be OK. Another modification (a good one) is that the client has revised the lists, so the longest is now "only" 62 items long (instead of the many hundreds they had before). The categories will still mostly contain zero, one, or two selected items, possibly a couple more if the user was overzealous. As far as OS and stuff, the site is in classic asp (quit snickering!), the server-side code is VBScript, and so far we've avoided the various Javascript libraries by the simple expedient of almost never using client-side scripting. This one form for this one client is currently the big exception. Give 'em an inch and they want a mile... Oh, and I have to add: I suck at Javascript, or really at any C-descendant language. Curly braces give me hives. I'd really, really like something I can just copy & paste into my page, maybe tweak some variable names, and never look at it again. A girl can dream, can't she? :) [existing code deleted because it's largely irrelevant.]

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• Generic linked list in c++

  - by itsaboy

  I have been struggling for too long a time now with a rather simple question about how to create a generic linked list in c++. The list should be able contain several types of structs, but each list will only contain one type of struct. The problem arises when I want to implement the getNode() function [see below], because then I have to specify which of the structs it should return. I have tried to substitute the structs with classes, where the getNode function returns a base class that is inherited by all the other classes, but it still does not do the trick, since the compiler does not allow the getNode function to return anything but the base class then. So here is some code snippet: typedef struct struct1 { int param1; (...) } struct1; typedef struct struct2 { double param1; (...) } struct2; typedef struct node { struct1 data; node* link; } node; class LinkedList { public: node *first; int nbrOfNodes; LinkedList(); void addNode(struct1); struct1 getNode(); bool isEmpty(); }; LinkedList::LinkedList() { first = NULL; nbrOfNodes = 0; } void LinkedList::addNode(struct1 newData) { if (nbrOfNodes == 0) { first = new node; first->data = newData; } else { node *it = first; for (int i = 0; i < nbrOfNodes; i++) { it = it->link; } node *newNode = new node; newNode->data = newData; it->link = newNode; } nbrOfNodes++; } bool LinkedList::isEmpty() { return !nbrOfNodes; } struct1 LinkedList::getNode() { param1 returnData = first->data; node* deleteNode = first; nbrOfNodes--; if (nbrOfNodes) first = deleteNode->link; delete deleteNode; return returnData; } So the question, put in one sentence, is as follows: How do I adjust the above linked list class so that it can also be used for struct2, without having to create a new almost identical list class for struct2 objects? As I said above, each instance of LinkedList will only deal with either struct1 or struct2. Grateful for hints or help

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• Using pointers, references, handles to generic datatypes, as generic and flexible as possible

  - by Patrick

  In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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• How to overwrite an array of char pointers with a larger list of char pointers?

  - by Casey

  My function is being passed a struct containing, among other things, a NULL terminated array of pointers to words making up a command with arguments. I'm performing a glob match on the list of arguments, to expand them into a full list of files, then I want to replace the passed argument array with the new expanded one. The globbing is working fine, that is, g.gl_pathv is populated with the list of expected files. However, I am having trouble copying this array into the struct I was given. #include <glob.h> struct command { char **argv; // other fields... } void myFunction( struct command * cmd ) { char **p = cmd->argv; char* program = *p++; // save the program name (e.g 'ls', and increment to the first argument glob_t g; memset(&g, 0, sizeof(g)); g.gl_offs = 1; int res = glob(*p++, GLOB_DOOFFS, NULL, &g); glob_handle_res(res); while (*p) { res = glob(*p, GLOB_DOOFFS | GLOB_APPEND, NULL, &g); glob_handle_res(res); } if( g.gl_pathc <= 0 ) { globfree(&g); } cmd->argv = malloc((g.gl_pathc + g.gl_offs) * sizeof *cmd->argv); if (cmd->argv == NULL) { sys_fatal_error("pattern_expand: malloc failed\n");} // copy over the arguments size_t i = g.gl_offs; for (; i < g.gl_pathc + g.gl_offs; ++i) cmd->argv[i] = strdup(g.gl_pathv[i]); // insert the original program name cmd->argv[0] = strdup(program); ** cmd->argv[g.gl_pathc + g.gl_offs] = 0; ** globfree(&g); } void command_free(struct esh_command * cmd) { char ** p = cmd->argv; while (*p) { free(*p++); // Segfaults here, was it already freed? } free(cmd->argv); free(cmd); } Edit 1: Also, I realized I need to stick program back in there as cmd-argv[0] Edit 2: Added call to calloc Edit 3: Edit mem management with tips from Alok Edit 4: More tips from alok Edit 5: Almost working.. the app segfaults when freeing the command struct Finally: Seems like I was missing the terminating NULL, so adding the line: cmd->argv[g.gl_pathc + g.gl_offs] = 0; seemed to make it work.

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• Separate specific #ifdef branches

  - by detly

  In short: I want to generate two different source trees from the current one, based only on one preprocessor macro being defined and another being undefined, with no other changes to the source. If you are interested, here is my story... In the beginning, my code was clean. Then we made a new product, and yea, it was better. But the code saw only the same peripheral devices, so we could keep the same code. Well, almost. There was one little condition that needed to be changed, so I added: #if defined(PRODUCT_A) condition = checkCat(); #elif defined(PRODUCT_B) condition = checkCat() && checkHat(); #endif ...to one and only one source file. In the general all-source-files-include-this header file, I had: #if !(defined(PRODUCT_A)||defined(PRODUCT_B)) #error "Don't make me replace you with a small shell script. RTFM." #endif ...so that people couldn't compile it unless they explicitly defined a product type. All was well. Oh... except that modifications were made, components changed, and since the new hardware worked better we could significantly re-write the control systems. Now when I look upon the face of the code, there are more than 60 separate areas delineated by either: #ifdef PRODUCT_A ... #else ... #endif ...or the same, but for PRODUCT_B. Or even: #if defined(PRODUCT_A) ... #elif defined(PRODUCT_B) ... #endif And of course, sometimes sanity took a longer holiday and: #ifdef PRODUCT_A ... #endif #ifdef PRODUCT_B ... #endif These conditions wrap anywhere from one to two hundred lines (you'd think that the last one could be done by switching header files, but the function names need to be the same). This is insane. I would be better off maintaining two separate product-based branches in the source repo and porting any common changes. I realise this now. Is there something that can generate the two different source trees I need, based only on PRODUCT_A being defined and PRODUCT_B being undefined (and vice-versa), without touching anything else (ie. no header inclusion, no macro expansion, etc)?

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