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• How to Open Multiple PopUp windows with JQuery on form submission (popUps should be relative to form

  - by Ole Jak

  I have A HTML form like this: <form> <fieldset class="ui-widget-content ui-corner-all"> <select id="Streams" class="multiselect ui-widget-content ui-corner-all" multiple="multiple" name="Streams[]"> <option value="35"> Example Name (35)</option> <option value="44"> Example Name (44)</option> <option value="5698"> Example Name (5698)</option> <option value="777"> Example Name (777)</option> <option value="12"> Example Name (12)</option> </select> <input type="submit" class="ui-state-default ui-corner-all" name="submitForm" id="submitForm" value="Play Stream from selected URL's!"/> </fieldset> </form> in my JS + HTML page I use JQuery. As you can see I allow user to select multiple Items. I want to open on Submit button click as many popup windows as many Items he selected in a list. Each popUp window should open some url like www.example.com/test.php?id=OPTION_SELECTED . And here I mean by PopUp Window a real browser window. So for each of the selected options I ll get a pop up window whith diferent url. Please Help.

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• iPhone NSCFString leaks in fetchRequest

  - by camilo

  In the following code: - (NSMutableArray *) fetchNotesForGroup: (NSString *)groupName { // Variables declaration NSMutableArray *result; NSFetchRequest *fetchRequest; NSEntityDescription *entity; NSSortDescriptor *sortDescriptor; NSPredicate *searchPredicate; NSError *error = nil; // Creates the fetchRequest and executes it fetchRequest = [[[NSFetchRequest alloc] init] autorelease]; entity = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"noteName" ascending:YES] autorelease]; [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]]; [fetchRequest setReturnsDistinctResults:YES]; searchPredicate = [NSPredicate predicateWithFormat:@"categoryName like %@", groupName]; [fetchRequest setPredicate:searchPredicate]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:@"noteName"]]; result = [[managedObjectContext executeFetchRequest:fetchRequest error:&error] mutableCopy]; // Variables release return result; } ... I Fetch notes for a given categoryName. When I'm running Instruments, it says that a NSCFString is leaking. I know leaks are mean for iPhone developers... but I don't have any idea on how to plug this one. Any clues? All help is welcome. Thanks a lot!

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• Initializing objects on the fly

  - by pocoa

  I have a vector called players and a class called Player. And what I'm trying to do is to write: players.push_back(Player(name, Weapon(bullets))); So I want to be able to create players in a loop. But I see an error message says "no matching function for call Player::Player..." Then I've changed that to: Weapon w(bullets); Player p(name, w); players.push_back(p); Here is my Player definition: class Player { public: Player(string &name, Weapon &weapon); private string name; Weapon weapon; } I'm just trying to learn what is the difference between these definitions. And is this the right way to pass an object to an object constructor. Note: These are not my actual class definitions. I'm just trying to learn something about object oriented programming in C++ with coding it. I mean I know that Weapon should be initialized in Player :)

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• php funciton problem

  - by Holian

  Hello, i have this little script, which should ping the IPs in the host_to_ping array. This php is called with JS in the index.html. But somethin' wrong, 'coz the $rval is always 1 (which mean the host is unreachable). But i know that the first two host is alive. So i print the $res variable, and i see the message: Need to give the IP. I dont understand why dont replace the $host variable to the actual IP address in the function. <?php function ping($host) { exec(sprintf('ping -n 4', escapeshellarg($host)), $res, $rval); print_r($res); return $rval === 0; } $hosts_to_ping = array('10.54.23.254', '10.22.23.254', '10.23.66.134'); ?> <ul> <?php foreach ($hosts_to_ping as $host): ?> <li> <?php echo $host; ?> <?php $up = ping($host); ?> (<img src="<?php echo $up ? 'on' : 'off'; ?>" alt="<?php echo $up ? 'up' : 'down'; ?>">) </li> <?php endforeach; ?> </ul>

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• Truly declarative language?

  - by gjvdkamp

  Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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• File Enumeration with ANT

  - by 1ndivisible

  I feel like I'm missing something obvious at the moment. I want to collect a set of dirs / files together in ANT. I know I can do it using a fileset with an optional patternset inside it, but that involves searching for files based a specific criterior - filetype, name etc. I already know the paths to the files I want to collect. I have n properties which reference these paths. I want a way to collect these paths in a fileset, though I cannot find a way to do it. This represents what I want to achieve (I know it isn't valid code, but hopefully it will describe what I mean): <fileset> <path>${src.dir}</path> <path>${test.dir}</path> <path>${third.party.src.dir}</path> <path>${bin.dir}</path> <path>${docs.build.txt}</path> </fileset>

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• What's a way for a client to automatically resolve the ip address of a server?

  - by zooropa

  The project I am working on is a client/server architecture. In a LAN environment, I want the client's to be able to automatically determine the server's address. I want to avoid having to manually configure each client with the ip address of the server. What is the best way to do this? Some alternatives I have thought about doing are: The server could listen for broadcast packets from the clients. The message from the client would be a request for the IP address of the server. The server would respond with its address. The machine running my project's server could also have a bind server running. The LAN's router could be configured to use it as one of its DNS servers. I think I saw that there is a bind library. Does that mean I can build the bind service into my server so that bind doesn't have to be installed on the server? Any other ideas? What have you done in the past? What are the pros/cons of these approaches and others that might be suggested? Thanks for your help!

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• Py_INCREF/DECREF: When

  - by Izz ad-Din Ruhulessin

  Is one correct in stating the following: If a Python object is created in a C function, but the function doesn't return it, no INCREF is needed, but a DECREF is. [false]If the function does return it, you do need to INCREF, in the function that receives the return value.[/false] When assigning C typed variables as attributes, like double, int etc., to the Python object, no INCREF or DECREF is needed. Assigning Python objects as attributes to your other Python objects goes like this: PyObject *foo; foo = bar // A Python object tmp = self->foo; Py_INCREF(foo); self->foo = foo; Py_XDECREF(tmp); //taken from the manual, but it is unclear if this works in every situation EDIT: -- can I safely use this in every situation? (haven't run into one where it caused me problems) dealloc of a Python object needs to DECREF for every other Python object that it has as an attribute, but not for attributes that are C types. Edit With 'C type as an attribute I mean bar and baz: typedef struct { PyObject_HEAD PyObject *foo; int bar; double baz; } FooBarBaz;

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• Detection of negative integers using bit operations

  - by Nawaz

  One approach to check if a given integer is negative or not, could be this: (using bit operations) int num_bits = sizeof(int) * 8; //assuming 8 bits per byte! int sign_bit = given_int & (1 << (num_bits-1)); //sign_bit is either 1 or 0 if ( sign_bit ) { cout << "given integer is negative"<<endl; } else { cout << "given integer is positive"<<endl; } The problem with this solution is that number of bits per byte couldn't be 8, it could be 9,10, 11 even 16 or 40 bits per byte. Byte doesn't necessarily mean 8 bits! Anyway, this problem can be easily fixed by writing, //CHAR_BIT is defined in limits.h int num_bits = sizeof(int) * CHAR_BIT; //no assumption. It seems fine now. But is it really? Is this Standard conformant? What if the negative integer is not represented as 2's complement? What if it's representation in a binary numeration system that doesn't necessitate only negative integers to have 1 in it's most significant bit? Can we write such code that will be both portable and standard conformant? Related topics: Size of Primitive data types Why is a boolean 1 byte and not 1 bit of size?

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• Getting table schema from a query

  - by Appu

  As per MSDN, SqlDataReader.GetSchemaTable returns column metadata for the query executed. I am wondering is there a similar method that will give table metadata for the given query? I mean what tables are involved and what aliases it has got. In my application, I get the query and I need to append the where clause programically. Using GetSchemaTable(), I can get the column metadata and the table it belongs to. But even though table has aliases, it still return the real table name. Is there a way to get the aliase name for that table? Following code shows getting the column metadata. const string connectionString = "your_connection_string"; string sql = "select c.id as s,c.firstname from contact as c"; using(SqlConnection connection = new SqlConnection(connectionString)) using(SqlCommand command = new SqlCommand(sql, connection)) { connection.Open(); SqlDataReader reader = command.ExecuteReader(CommandBehavior.KeyInfo); DataTable schema = reader.GetSchemaTable(); foreach (DataRow row in schema.Rows) { foreach (DataColumn column in schema.Columns) { Console.WriteLine(column.ColumnName + " = " + row[column]); } Console.WriteLine("----------------------------------------"); } Console.Read(); } This will give me details of columns correctly. But when I see BaseTableName for column Id, it is giving contact rather than the alias name c. Is there any way to get the table schema and aliases from a query like the above? Any help would be great!

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• APplication performance issue : SqlServer & Oracle

  - by Mahesh

  Hi, We have a applicaiton in Silverlight,WCF, NHibernate. Currently it is supporting SQL Serve and Oracle database. As it's huge data, it is running ok on SQL Sevrer. But on Oracle it is running very slow. For one functionality it takes 5 Sec to execute on SQL Server and 30 Sec on Oracle. I am not able to figure out what will be issue. Two things that i want to share with you about our database. 1) Database: contains one base table contains column of type SQLServer: [Text] Oracle: [NCLOB] 2) Our database structure is too much normalized. May be in the oracle i have used NCLOB, that is the cause of the performance. I mean i don't know the details about it.... Can anyone please let me know what will be cause? Or Which actions do i need to follw to improve the performance as equal as SqlServer.? Thanks in advance. Mahesh.

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• A commercial software but open and free for personal/edu. How to license?

  - by Ivan

  I am developing a software to sell for business use but am willing to make it free and open-source for personal and educational use. Actually I can see the flowing requirements I would like the license to set: Personal and educational usage of the program and its source codes is to be free. In case of publishing of derivative works the original work and author (me) must be mentioned (incl. textual link to my website in a not-very-far-hidden place) and the derivative work must have different name. A derivative work can be closed-source. In every case of commercial (when the end-user is a commercial body (as a company (expect of non-profit organizations), an individual entrepreneur or government office)) usage of my work or any of derivative works made by anyone, the end-user, service provider or the derivative author must buy a commercial license from me. I mean no guarantees or responsibilities, whether expressed or implied... (except the case when one explicitly purchases a support service contract from me and the particular contract specifies a responsibility). Is there a known common license for this case? As far as I can see now it can not be OSI-approved as it does not comply to the §6. of OSI definition of open source. But there still can be an a common known reusable license for this case as it looks quite natural, I think.

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• ControlCollection extension method optimazation

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• Regular input in ASP.NET

  - by coffeeaddict

  Here's an example of a regular standard HTML input for my radiobuttonlist: <label><input type="radio" name="rbRSelectionGroup" checked value="0" />None</label> <asp:Repeater ID="rptRsOptions" runat="server"> <ItemTemplate> <div> <label><input type="radio" name="rbRSelectionGroup" value='<%# ((RItem)Container.DataItem).Id %>' /><%# ((RItem)Container.DataItem).Name %></label> </div> </ItemTemplate> </asp:Repeater> I removed some stuff for this thread, one being I put an r for some name that I do not want to expose here so just an fyi. Now, I would assume that this would or should happen: Page loads the first time, the None radio button is checked / defaulted I go and select a different radiobutton in this radiobutton list I do an F5 refresh in my browser The None radio button is pre-selected again after it has come back from the refresh but #4 is not happening. It's retaining the radiobutton that I selected in #2 and I don't know why. I mean in regular HTML it's stateless. So what could be holding this value? I want this to act like a normal input button. I know the question of "why not use an ASP.NET control" will come up. Well there are 2 reasons: The stupid radiobuttonlist bug that everyone knows about I just want to brush up more on standard input tags We are not moving to MVC so this is as close as I'll get and it's ok, because the rest of the team is on par with having mixed ASP.NET controls with standard HTML controls in our pages Anyway my main question here is I'm surprised that it's retaining the change in selection after postback.

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• How OpenStack Swift handles concurrent restful API request?

  - by Chen Xie

  I installed a swift service and was trying to know the capability of handling concurrent request. So I created massive amount of threads in Java, and sent it via the RestFUL API Not surprisingly, when the number of requests climb up, the program started to throw out exceptions. Caused by: java.net.ConnectException: Connection timed out: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:69) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391) at java.net.Socket.connect(Socket.java:579) at java.net.Socket.connect(Socket.java:528) at sun.net.NetworkClient.doConnect(NetworkClient.java:180) at sun.net.www.http.HttpClient.openServer(HttpClient.java:378) at sun.net.www.http.HttpClient.openServer(HttpClient.java:473) at sun.net.www.http.HttpClient.(HttpClient.java:203) But can anyone tell me how that time outhappened? I am curious of how SWIFT handles those requests. Is that by queuing the requests and because there are too many requests in the queue and wait for too long time and it's just get kicked out from the queue? If this holds, does it mean that it's an asynchronized mechanism to handle requests? Thanks.

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• Releasing Excel after using Interop

  - by figus

  Hi everyone I've read many post looking for my answer, but all are similar to this: http://stackoverflow.com/questions/1610743/reading-excel-files-in-vb-net-leaves-excel-process-hanging My problem is that I don't quit the app... The idea is this: If a User has Excel Open, if he has the file I'm interested in open... get that Excel instance and do whatever I want to do... But I don't to close his File after I'm done... I want him to keep working on it, the problem is that when he closes Excel... The process keeps running... and running... and running after the user closes Excel with the X button... this is how I try to do it This piece is used to know if he has Excel open, and in the For I check for the file name I'm interested in. Try oApp = GetObject(, "Excel.Application") libroAbierto = True For Each libro As Microsoft.Office.Interop.Excel.Workbook In oApp.Workbooks If libro.Name = EquipoASeccionIdSeccion.Text & ".xlsm" Then Exit Try End If Next libroAbierto = False Catch ex As Exception oApp = New Microsoft.Office.Interop.Excel.Application End Try here would be my code... if he hasn't Excel open, I create a new instance, open the file and everything else. My code ends with this: If Not libroAbierto Then libroSeccion.Close(SaveChanges:=True) oApp.Quit() Else oApp.UserControl = True libroSeccion.Save() End If System.Runtime.InteropServices.Marshal.FinalReleaseComObject(libroOriginal) System.Runtime.InteropServices.Marshal.FinalReleaseComObject(libroSeccion) System.Runtime.InteropServices.Marshal.FinalReleaseComObject(origen) System.Runtime.InteropServices.Marshal.FinalReleaseComObject(copiada) System.Runtime.InteropServices.Marshal.FinalReleaseComObject(oApp) libroOriginal = Nothing libroSeccion = Nothing oApp = Nothing origen = Nothing copiada = Nothing nuevosGuardados = True So you can see that, if I opened the file, I call oApp.Quit() and everything else and the Excel Process ends after a few seconds (maybe 5 aprox.) BUT if I mean the user to keep the file open (not calling Quit()), Excel process keeps running after the user closes Excel with the X button. Is there any way to do what I try to do?? Control a open instance of excel and releasing everything so when the user closes it with the X button, the Excel Process dies normally??? Thanks!!!

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• jQuery .trigger() or $(window) not working in Google Chrome

  - by Jonathan

  I have this jQuery ajax navigation tabs plugin that I created using some help from CSS-Tricks.com and the jQuery hashchange event plugin (detects hash changes in browsers that don't support it). The code is little long to post it here but it goes something like this: Part 1) When a tab is clicked, it gets the href attribute of that tab and add it to the browsers navigation bar like '#tab_name': window.location.hash = $(this).attr("href"); Part 2) When the navigation bar changes (hash change), it gets the href change like this: window.location.hash.substring(1); (substring is to get only 'tab_name' without the '#'), and then call the ajax function to get the info to display. I want to automatically trigger the plugin to load the first tab when the page is accessed, so at the start of the code I put: if (window.location.hash === '') { // If no '#' is in the browser navigation bar window.location.hash = '#tab_1'; // Add #tab_1 to the navigation bar $(window).trigger('hashchange'); // Trigger a hashchange so 'Part 2' of the plugin calls the ajax function using the '#tab_1' added } The probles is that it works in FF but not in Chrome, I mean, everything works but it seems like the $(window).trigger('hashchange'); is not working because it doesnt get the first tab.. Any suggestions??

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• Find min. "join" operations for sequence

  - by utyle

  Let's say, we have a list/an array of positive integers x1, x2, ... , xn. We can do a join operation on this sequence, that means that we can replace two elements that are next to each other with one element, which is sum of these elements. For example: - array/list: [1;2;3;4;5;6] we can join 2 and 3, and replace them with 5; we can join 5 and 6, and replace them with 11; we cannot join 2 and 4; we cannot join 1 and 3 etc. Main problem is to find minimum join operations for given sequence, after which this sequence will be sorted in increasing order. Note: empty and one-element sequences are sorted in increasing order. Basic examples: for [4; 6; 5; 3; 9] solution is 1 (we join 5 and 3) for [1; 3; 6; 5] solution is also 1 (we join 6 and 5) What I am looking for, is an algorithm that solve this problem. It could be in pseudocode, C, C++, PHP, OCaml or similar (I mean: I woluld understand solution, if You wrote solution in one of these languages). I would appreciate Your help.

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• C# adding list into list

  - by gencay

  I have a DocumentList.c as implemented below. And when I try to add a list into the instance of DocumentList object it adds but the others be the same class DocumentList { public static List wordList; public static string type; public static string path; public static double cos; public static double dice; public static double jaccard; //public static string title; public DocumentList(List wordListt, string typee, string pathh, double sm11, double sm22, double sm33) { type = typee; wordList = wordListt; path = pathh; cos = sm11; dice = sm22; jaccard = sm33; } } in main c#code fragment public partial class Window1 : System.Windows.Window { static private List documentList = new List(); ... in a method I use as below. DocumentList dt = new DocumentList(para1, para2, para3, para4, para5, para6); documentList.Add(dt); Now, When i add the first list it is ok it seems 1 item in documentList, but for the second one I get a list with 2 items but both the same.. I mean I cannot keep previous list item..

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• Execute process conditionally in Windows PowerShell (e.g. the && and || operators in Bash)

  - by Dustin

  I'm wondering if anybody knows of a way to conditionally execute a program depending on the exit success/failure of the previous program. Is there any way for me to execute a program2 immediately after program1 if program1 exits successfully without testing the LASTEXITCODE variable? I tried the -band and -and operators to no avail, though I had a feeling they wouldn't work anyway, and the best substitute is a combination of a semicolon and an if statement. I mean, when it comes to building a package somewhat automatically from source on Linux, the && operator can't be beaten: # Configure a package, compile it and install it ./configure && make && sudo make install PowerShell would require me to do the following, assuming I could actually use the same build system in PowerShell: # Configure a package, compile it and install it .\configure ; if ($LASTEXITCODE -eq 0) { make ; if ($LASTEXITCODE -eq 0) { sudo make install } } Sure, I could use multiple lines, save it in a file and execute the script, but the idea is for it to be concise (save keystrokes). Perhaps it's just a difference between PowerShell and Bash (and even the built-in Windows command prompt which supports the && operator) I'll need to adjust to, but if there's a cleaner way to do it, I'd love to know.

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• django + south + python: strange behavior when using a text string received as a parameter in a func

  - by carlosescri

  Hello, this is my first question. I'm trying to execute a SQL query in django (south migration): from django.db import connection # ... class Migration(SchemaMigration): # ... def transform_id_to_pk(self, table): try: db.delete_primary_key(table) except: pass finally: cursor = connection.cursor() # This does not work cursor.execute('SELECT MAX("id") FROM "%s"', [table]) # I don't know if this works. try: minvalue = cursor.fetchone()[0] except: minvalue = 1 seq_name = table + '_id_seq' db.execute('CREATE SEQUENCE "%s" START WITH %s OWNED BY "%s"."id"', [seq_name, minvalue, table]) db.execute('ALTER TABLE "%s" ALTER COLUMN id SET DEFAULT nextval("%s")', [table, seq_name + '::regclass']) db.create_primary_key(table, ['id']) # ... I use this function like this: self.transform_id_to_pk('my_table_name') So it should: Find the biggest existent ID or 0 (it crashes) Create a sequence name Create the sequence Update the ID field to use sequence Update the ID as PK But it crashes and the error says: File "../apps/accounting/migrations/0003_setup_tables.py", line 45, in forwards self.delegation_table_setup(orm) File "../apps/accounting/migrations/0003_setup_tables.py", line 478, in delegation_table_setup self.transform_id_to_pk('accounting_delegation') File "../apps/accounting/migrations/0003_setup_tables.py", line 20, in transform_id_to_pk cursor.execute(u'SELECT MAX("id") FROM "%s"', [table.encode('utf-8')]) File "/Library/Python/2.6/site-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) psycopg2.ProgrammingError: relation "E'accounting_delegation'" does not exist LINE 1: SELECT MAX("id") FROM "E'accounting_delegation'" ^ I have shortened the file paths for convenience. What does that "E'accounting_delegation'" mean? How could I get rid of it? Thank you! Carlos.

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• Python raw strings and trailing back slashes.

  - by dash-tom-bang

  I ran across something once upon a time and wondered if it was a Python "bug" or at least a misfeature. I'm curious if anyone knows of any justifications for this behavior. I thought of it just now reading "Code Like a Pythonista," which has been enjoyable so far. I'm only familiar with the 2.x line of Python. Raw strings are strings that are prefixed with an r. This is great because I can use backslashes in regular expressions and I don't need to double everything everywhere. It's also handy for writing throwaway scripts on Windows, so I can use backslashes there also. (I know I can also use forward slashes, but throwaway scripts often contain content cut&pasted from elsewhere in Windows.) So great! Unless, of course, you really want your string to end with a backslash. There's no way to do that in a 'raw' string. In [9]: r'\n' Out[9]: '\\n' In [10]: r'abc\n' Out[10]: 'abc\\n' In [11]: r'abc\' ------------------------------------------------ File "<ipython console>", line 1 r'abc\' ^ SyntaxError: EOL while scanning string literal In [12]: r'abc\\' Out[12]: 'abc\\\\' So one slash before the closing quote is an error, but two slashes gives you two slashes! Certainly I'm not the only one that is bothered by this? Thoughts on why 'raw' strings are 'raw, except for slash-quote'? I mean, if I wanted to embed a single quote in there I'd just use double quotes around the string, and vice versa. If I wanted both, I'd just triple quote. If I really wanted three quotes in a row in a raw string, well, I guess I'd have to deal, but is this considered "proper behavior"?

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• How can I make a family of singletons?

  - by Jay

  I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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• Lookup table size reduction

  - by Ryan

  Hello: I have an application in which I have to store a couple of millions of integers, I have to store them in a Look up table, obviously I cannot store such amount of data in memory and in my requirements I am very limited I have to store the data in an embebedded system so I am very limited in the space, so I would like to ask you about recommended methods that I can use for the reduction of the look up table. I cannot use function approximation such as neural networks, the values needs to be in a table. The range of the integers is not known at the moment. When I say integers I mean a 32 bit value. Basically the idea is use some copmpression method to reduce the amount of memory but without losing many precision. This thing needs to run in hardware so the computation overhead cannot be very high. In my algorithm I have to access to one value of the table do some operations with it and after update the value. In the end what I should have is a function which I pass an index to it and then I get a value, and after I have to use another function to write a value in the table. I found one called tile coding http://www.cs.ualberta.ca/~sutton/book/8/node6.html, this one is based on several look up tables, does anyone know any other method?. Thanks.

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• Very slow guards in my monadic random implementation (haskell)

  - by danpriduha

  Hi! I was tried to write one random number generator implementation, based on number class. I also add there Monad and MonadPlus instance. What mean "MonadPlus" and why I add this instance? Because of I want to use guards like here: -- test.hs -- import RandomMonad import Control.Monad import System.Random x = Rand (randomR (1 ::Integer, 3)) ::Rand StdGen Integer y = do a <-x guard (a /=2) guard (a /=1) return a here comes RandomMonad.hs file contents: -- RandomMonad.hs -- module RandomMonad where import Control.Monad import System.Random import Data.List data RandomGen g => Rand g a = Rand (g ->(a,g)) | RandZero instance (Show g, RandomGen g) => Monad (Rand g) where return x = Rand (\g ->(x,g)) (RandZero)>>= _ = RandZero (Rand argTransformer)>>=(parametricRandom) = Rand funTransformer where funTransformer g | isZero x = funTransformer g1 | otherwise = (getRandom x g1,getGen x g1) where x = parametricRandom val (val,g1) = argTransformer g isZero RandZero = True isZero _ = False instance (Show g, RandomGen g) => MonadPlus (Rand g) where mzero = RandZero RandZero `mplus` x = x x `mplus` RandZero = x x `mplus` y = x getRandom :: RandomGen g => Rand g a ->g ->a getRandom (Rand f) g = (fst (f g)) getGen :: RandomGen g => Rand g a ->g -> g getGen (Rand f) g = snd (f g) when I run ghci interpreter, and give following command getRandom y (mkStdGen 2000000000) I can see memory overflow on my computer (1G). It's not expected, and if I delete one guard, it works very fast. Why in this case it works too slow? What I do wrong?

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