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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• Rails: Oracle constraint violation

  - by justinbach

  I'm doing maintenance work on a Rails site that I inherited; it's driven by an Oracle database, and I've got access to both development and production installations of the site (each with its own Oracle DB). I'm running into an Oracle error when trying to insert data on the production site, but not the dev site: ActiveRecord::StatementInvalid (OCIError: ORA-00001: unique constraint (DATABASE_NAME.PK_REGISTRATION_OWNERSHIP) violated: INSERT INTO registration_ownerships (updated_at, company_ownership_id, created_by, updated_by, registration_id, created_at) VALUES ('2006-05-04 16:30:47', 3, NULL, NULL, 2920, '2006-05-04 16:30:47')): /usr/local/lib/ruby/gems/1.8/gems/activerecord-oracle-adapter-1.0.0.9250/lib/active_record/connection_adapters/oracle_adapter.rb:221:in `execute' app/controllers/vendors_controller.rb:94:in `create' As far as I can tell (I'm using Navicat as an Oracle client), the DB schema for the dev site is identical to that of the live site. I'm not an Oracle expert; can anyone shed light on why I'd be getting the error in one installation and not the other? Incidentally, both dev and production registration_ownerships tables are populated with lots of data, including duplicate entries for country_ownership_id (driven by index PK_REGISTRATION_OWNERSHIP). Please let me know if you need more information to troubleshoot. I'm sorry I haven't given more already, but I just wasn't sure which details would be helpful.

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• SQL Concurrent test update question

  - by ptoinson

  Howdy Folks, I have a SQLServer 2008 database in which I have a table for Tags. A tag is just an id and a name. The definition of the tags table looks like: CREATE TABLE [dbo].[Tag]( [ID] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](255) NOT NULL CONSTRAINT [PK_Tag] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ) Name is also a unique index. further I have several processes adding data to this table at a pretty rapid rate. These processes use a stored proc that looks like: ALTER PROC [dbo].[lg_Tag_Insert] @Name varchar(255) AS DECLARE @ID int SET @ID = (select ID from Tag where Name=@Name ) if @ID is null begin INSERT Tag(Name) VALUES (@Name) RETURN SCOPE_IDENTITY() end else begin return @ID end My issues is that, other than being a novice at concurrent database design, there seems to be a race condition that is causing me to occasionally get an error that I'm trying to enter duplicate keys (Name) into the DB. The error is: Cannot insert duplicate key row in object 'dbo.Tag' with unique index 'IX_Tag_Name'. This makes sense, I'm just not sure how to fix this. If it where code I would know how to lock the right areas. SQLServer is quite a different beast. First question is what is the proper way to code this 'check, then update pattern'? It seems I need to get an exclusive lock on the row during the check, rather than a shared lock, but it's not clear to me the best way to do that. Any help in the right direction will be greatly appreciated. Thanks in advance.

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• Rails paginate array items one-by-one instead of page-by-page

  - by hnovick

  Hi Guys, I have a group of assets, let's call them "practitioners". I'm displaying these practitioners in the header of a calendar interface. There are 7 columns to the calendar. 7 columns = 7 practitioners per view/page. Right now: if the first page shows you practitioners 1-7, when you go the next page you will see practitioners 8-15, next page 16-23, etc. etc. i am wondering how to page the practitioners so that if the first page shows you practitioners 1-7, the next page will show you practitioners 2-8, then 3-9, etc. etc. i would greatly appreciate any help you can offer. here is the rails code i am working with. best regards, harris novick # get the default sort order sort_order = RESOURCE_SORT_ORDER # if we've been given asset ids, start our list with them unless params[:asset_ids].blank? params[:asset_ids] = params[:asset_ids].values unless params[:asset_ids].is_a?(Array) sort_order = "#{params[:asset_ids].collect{|id| "service_provider_resources.id = #{id} DESC"}.join(",")}, #{sort_order}" end @asset_set = @provider.active_resources(:include => {:active_services => :latest_approved_version}).paginate( :per_page => RESOURCES_IN_DAY_VIEW, :page => params[:page], :order => sort_order )

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• How to gray out HTML form inputs?

  - by typoknig

  What is the best way to gray out text inputs on an HTML form? I need the inputs to be grayed out when a user checks a check box. Do I have to use JavaScript for this (not very familiar with JScript) or can I use PHP (which I am more familiar with)? EDIT: After some reading I have got a little bit of code, but it is giving me problems. For some reason I cannot get my script to work based on the state of the form input (enabled or disabled) or the state of my checkbox (checked or unchecked), but my script works fine when I base it on the values of the form inputs. I have written my code exactly like several examples online (mainly this one) but to no avail. None of the stuff that is commented out will work. What am I doing wrong here? <label>Mailing address same as residental address</label> <input name="checkbox" onclick="disable_enable() "type="checkbox" style="width:15px"/><br/><br/> <script type="text/javascript"> function disable_enable(){ if (document.form.mail_street_address.value==1) document.form.mail_street_address.value=0; //document.form.mail_street_address.disabled=true; //document.form.mail_city.disabled=true; //document.form.mail_state.disabled=true; //document.form.mail_zip.disabled=true; else document.form.mail_street_address.value=1; //document.form.mail_street.disabled=false; //document.form.mail_city.disabled=false; //document.form.mail_state.disabled=false; //document.form.mail_zip.disabled=false; } </script>

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• Serial.begin(speed, config) not compiling for Leonardo Board

  - by forgemo

  I would like to configure my serial communication to have no parity, 1 start- and 2 stop-bits. The documentation for Serial.begin(speed, config) states: (...) An optional second argument configures the data, parity, and stop bits. The default is 8 data bits, no parity, one stop bit. The documentation also lists the possible configuration-values. According to my (limited) understanding, I need SERIAL_7N2 or SERIAL_8N2 to meet my requirements. (I'm not sure how the data-bits relate to the the 1-start-bit that I need.) However, I can't even compile because I have no idea how to supply that config value to the begin method. (I don't have much Arduino/C++ experience) I've tried in my code the following two variants: Serial.begin(9600, SERIAL_8N2); Serial.begin(9600, "SERIAL_8N2"); Am I missing something? Additional Information: Serial.begin(speed, config) has been introduced with the latest Arduino 1.0.2 IDE version. The code defining/implementing the begin methods can be found here. HardwareSerial.h HardwareSerial.cpp Edit: According to the replies from PeterJ and borges, the following variant is correct. Serial.begin(9600, SERIAL_8N2); However, it's still not working. I found that the compile error doesn't occur if I change the configured board from my Arduino Leonardo to Arduino uno. Therefore, it could be a bug occurring only with a subset of boards ... or maybe it's not supported?!

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• LINQDataSource and private columns

  - by fyjham

  Hey, I was trying to use a ListView bound to a LinqDataSource to insert to a table where I had a few columns private to the table class (Specifically password columns - only access I want to give outside the class is methods that generate the salt and encrypt the password to store it in 1 go). I gave this a few shots, but I didn't come up with anything I really liked... was wondering if anyone has a better way to do this. The methods I've found: Use the LinqDataSource inserting event and make the appropriate calls on e.NewObject. I don't really like this because it's so far removed from the actual input and there's no simple way to hold the password in the meantime other than a class variable set during the ListView's inserting event (Which works, but seems a little dodgy). Open up these properties and just ask everyone to use the appropriate static methods for encoding the passwords they pass in. I don't really like this cause I'd prefer that class to enforce data integrity rather than relying on all calling code doing it properly... I'm currently going with option #1, but I don't really like passing values between events using class variables like that (It just seems unstructured... even though I can guarantee the events will happen in the right order). Does anyone know a better way, or alternatively am I being too pedantic and one of the methods above is actually the right way to go? Thanks

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• C# How to commit a TextBox?

  - by Jake

  Hi, In a form, I have a TextBox Binding an Object on its member property "Title". Along with it is a "Save" button to test the binding. Seems like the underlying object property does not get updated unless the textbox loses focus. But there no form.ActiveControl.Blur() for use. Besides, this does not seem like a sound hack. Anyway to do this better? Thanks. EDIT: Sorry for not being clear. My question is in the title: "How to commit a TextBox". I use the term "commit" from the DataGridView commit and BindingSource commit. And it's in WinForms. (Have never worked with WPF, so it didn't occur to me. Sorry). The actual scenario I have is I have a bunch of TextBox binded to property of a single Object. The user enters values in all the TextBox and when the user clicks save (toolbar button), the last TextBox is still in focus (or in editing mode) hence the save will not capture the last value in the last textbox. I want to find the correct way to "commit" the textbox value just before saving. Thanks.

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• Handling XMLHttpRequest to call external application

  - by Ian

  I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls. The situation: The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status. The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database. In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem. What I think I want: Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available). C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding. How do I do this? Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents? Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces? Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch? Thanks for any help! I am really having trouble learning about the server side of these technologies.

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• Why MKMapView region is different than requested?

  - by Kamil

  Greetings! I'm saving map region into user defaults when my iPhone app is closing like this: MKCoordinateRegion region = mapView.region; [[NSUserDefaults standardUserDefaults] setDouble:region.center.latitude forKey:@"map.location.center.latitude"]; [[NSUserDefaults standardUserDefaults] setDouble:region.center.longitude forKey:@"map.location.center.longitude"]; [[NSUserDefaults standardUserDefaults] setDouble:region.span.latitudeDelta forKey:@"map.location.span.latitude"]; [[NSUserDefaults standardUserDefaults] setDouble:region.span.longitudeDelta forKey:@"map.location.span.longitude"]; When app launches again, i read those values back the same way, so that the user can see exactly the same map view as it was last time: MKCoordinateRegion region; region.center.latitude = [[NSUserDefaults standardUserDefaults] doubleForKey:@"map.location.center.latitude"]; region.center.longitude = [[NSUserDefaults standardUserDefaults] doubleForKey:@"map.location.center.longitude"]; region.span.latitudeDelta = [[NSUserDefaults standardUserDefaults] doubleForKey:@"map.location.span.latitude"]; region.span.longitudeDelta = [[NSUserDefaults standardUserDefaults] doubleForKey:@"map.location.span.longitude"]; NSLog([NSString stringWithFormat:@"Region read : %f %f %f %f", region.center.latitude, region.center.longitude, region.span.latitudeDelta, region.span.longitudeDelta]); [mapView setRegion:region]; NSLog([NSString stringWithFormat:@"Region on map: %f %f %f %f", mapView.region.center.latitude, mapView.region.center.longitude, mapView.region.span.latitudeDelta, mapView.region.span.longitudeDelta]); The region I read from user defaults is (not surprisingly) exactly the same as when it was saved. Notice that what is saved comes directly from the map, so it's not transformed in any way. I set it back on map with setRegion: method, but then it is different! Example results: Region read : 50.241110 8.891555 0.035683 0.042915 Region on map: 50.241057 8.891544 0.050499 0.054932 Does anybody know why this happens?

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• Insert records using ExecuteNonQuery, showing exception that invalid column name

  - by tina

  Hi all, I am using SQL Server 2008. I want to insert records into a table using ExecuteNonQuery, for that I have written: customUtility.ExecuteNonQuery("insert into furniture_ProductAccessories(Product_id, Accessories_id, SkuNo, Description1, Price, Discount) values(" + prodid + "," + strAcc + "," + txtSKUNo.Text + "," + txtAccDesc.Text + "," + txtAccPrices.Text + "," + txtAccDiscount.Text + ")"); & following is ExecuteNonQuery function: public static bool ExecuteNonQuery(string SQL) { bool retVal = false; using (SqlConnection con = new SqlConnection(System.Web.Configuration.WebConfigurationManager.ConnectionStrings["dbConnect"].ToString())) { con.Open(); SqlTransaction trans = con.BeginTransaction(); SqlCommand command = new SqlCommand(SQL, con, trans); try { command.ExecuteNonQuery(); trans.Commit(); retVal = true; } catch(Exception ex) { //HttpContext.Current.Response.Write(SQL + "<br>" + ex.Message); //HttpContext.Current.Response.End(); } finally { // Always call Close when done reading. con.Close(); } return retVal; } } but it showing exception that invalid column name to Description1 and even it's value which coming from txtAccDesc.Text. I have tried by removing Description1 column, other records are getting inserted successfully. Could you please help me? Thanks.

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• PHP: How To Integrate HTML Purifier To Fileter User Submitted Data?

  - by TaG

  I have this script that collects data from users and I wanted to check their data for malicious code like XSS and SQL injections by using HTML Purifier http://htmlpurifier.org/ but how do I add it to my php form submission script? Here is my HTML purifier code require_once '../../htmlpurifier/library/HTMLPurifier.auto.php'; $config = HTMLPurifier_Config::createDefault(); $config->set('Core.Encoding', 'UTF-8'); // replace with your encoding $config->set('HTML.Doctype', 'XHTML 1.0 Strict'); // replace with your doctype $purifier = new HTMLPurifier($config); $clean_html = $purifier->purify($dirty_html); Here is my PHP form submission code. if (isset($_POST['submitted'])) { // Handle the form. $mysqli = mysqli_connect("localhost", "root", "", "sitename"); $dbc = mysqli_query($mysqli,"SELECT users.*, profile.* FROM users INNER JOIN contact_info ON contact_info.user_id = users.user_id WHERE users.user_id=3"); $about_me = mysqli_real_escape_string($mysqli, $_POST['about_me']); $interests = mysqli_real_escape_string($mysqli, $_POST['interests']); if (mysqli_num_rows($dbc) == 0) { $mysqli = mysqli_connect("localhost", "root", "", "sitename"); $dbc = mysqli_query($mysqli,"INSERT INTO profile (user_id, about_me, interests) VALUES ('$user_id', '$about_me', '$interests')"); } if ($dbc == TRUE) { $dbc = mysqli_query($mysqli,"UPDATE profile SET about_me = '$about_me', interests = '$interests' WHERE user_id = '$user_id'"); echo '<p class="changes-saved">Your changes have been saved!</p>'; } if (!$dbc) { // There was an error...do something about it here... print mysqli_error($mysqli); return; } }

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• BindingFlags.DeclaredOnly alternative to avoid ambiguous properties of derived classes

  - by JoeBilly

  I'am looking for a solution to access 'flatten' (lowest) properties values of a class and its derived via reflection by property names. ie access either Property1 or Property2 from the ClassB or ClassC type : public class ClassA { public virtual object Property1 { get; set; } public object Property2 { get; set; } } public class ClassB : ClassA { public override object Property1 { get; set; } } public class ClassC : ClassB { } Using simple reflection works until you have virtual properties that are overrired (ie Property1 from ClassB). Then you get a AmbiguousMatchException because the searcher don't know if you want the property of the main class or the derived. Using BindingFlags.DeclaredOnly avoid the AmbiguousMatchException but unoverrided virtual properties or derived classes properties are ommited (ie Property2 from ClassB). Is there an alternative to this poor workaround : // Get the main class property with the specified propertyName PropertyInfo propertyInfo = _type.GetProperty(propertyName, BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static); // If not found, get the property wherever it is if (propertyInfo == null) propertyInfo = _type.GetProperty(propertyName); Furthermore, this workaround not resolve the reflection of 2nd level properties : getting Property1 from ClassC and AmbiguousMatchException is back. My thoughts : I have no choice except loop... Erk... ?? I'am open to Emit, Lambda (is the Expression.Call can handle this?) even DLR solution. Thanks !

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• rake test not copying development postgres db with sequences

  - by Robert Crida

  I am trying to develop a rails application on postgresql using a sequence to increment a field instead of a default ruby approach based on validates_uniqueness_of. This has proved challenging for a number of reasons: 1. This is a migration of an existing table, not a new table or column 2. Using parameter :default = "nextval('seq')" didn't work because it tries to set it in parenthesis 3. Eventually got migration working in 2 steps: change_column :work_commencement_orders, :wco_number_suffix, :integer, :null => false#, :options => "set default nextval('wco_number_suffix_seq')" execute %{ ALTER TABLE work_commencement_orders ALTER COLUMN wco_number_suffix SET DEFAULT nextval('wco_number_suffix_seq'); } Now this would appear to have done the correct thing in the development database and the schema looks like: wco_number_suffix | integer | not null default nextval('wco_number_suffix_seq'::regclass) However, the tests are failing with PGError: ERROR: null value in column "wco_number_suffix" violates not-null constraint : INSERT INTO "work_commencement_orders" ("expense_account_id", "created_at", "process_id", "vo2_issued_on", "wco_template", "updated_at", "notes", "process_type", "vo_number", "vo_issued_on", "vo2_number", "wco_type_id", "created_by", "contractor_id", "old_wco_type", "master_wco_number", "deadline", "updated_by", "detail", "elective_id", "authorization_batch_id", "delivery_lat", "delivery_long", "operational", "state", "issued_on", "delivery_detail") VALUES(226, '2010-05-31 07:02:16.764215', 728, NULL, E'Default', '2010-05-31 07:02:16.764215', NULL, E'Procurement::Process', NULL, NULL, NULL, 226, NULL, 276, NULL, E'MWCO-213', '2010-06-14 07:02:16.756952', NULL, E'Name 4597', 220, NULL, NULL, NULL, 'f', E'pending', NULL, E'728 Test Road; Test Town; 1234; Test Land') RETURNING "id" The explanation can be found when you inspect the schema of the test database: wco_number_suffix | integer | not null So what happened to the default? I tried adding task: template: smmt_ops_development to the database.yml file which has the effect of issuing create database smmt_ops_test template = "smmt_ops_development" encoding = 'utf8' I have verified that if I issue this then it does in fact copy the default nextval. So clearly rails is doing something after that to suppress it again. Any suggestions as to how to fix this? Thanks Robert

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• DatagGridViewColumn.DataPropertyName to an array element?

  - by unknown

  Hi there, I'm using a DataGridView binding its datasource to a List, and specifying the properties for each column. An example would be: DataGridViewTextBoxColumn colConcept = new DataGridViewTextBoxColumn(); DataGridViewCell cell4 = new DataGridViewTextBoxCell(); colConcept.CellTemplate = cell4; colConcept.Name = "concept"; colConcept.HeaderText = "Concept"; colConcept.DataPropertyName = "Concept"; colConcept.Width = 200; this.dataGridViewBills.Columns.Add(colConcept); {... assign other colums...} And finally this.dataGridViewBills.DataSource=billslist; //billslist is List<Bill> Obviously Class Bill has a Property called Concept, as well as one Property for each column. Well, now my problem, is that Bill should have and Array/List/whateverdynamicsizecontainer of strings called Years. Let's assume that every Bill will have the same Years.Count, but this only known at runtime.Thus, I can't specify properties like Bill.FirstYear to obtain Bill.Years[0], Bill.SecondYear to obtain Bills.Years[1]... etc... and bind it to each column. The idea, is that now I want to have a grid with dynamic number of colums (known at runtime), and each column filled with a string from the Bill.Years List. I can make a loop to add columns to the grid at runtime depending of Bill.Years.Count, but is possible to bind them to each of the strings that the Bill.Years List contains??? I'm not sure if I'm clear enough. The result ideally would be something like this, for 2 bills on the list, and 3 years for each bill: --------------------------------------GRID HEADER------------------------------- NAME CONCEPT YEAR1 YEAR2 YEAR3 --------------------------------------GRID VALUES------------------------------- Bill1 Bill1.Concept Bill1.Years[0] Bill1.Years[1] Bill1.Years[2] Bill2 Bill2.Concept Bill2.Years[0] Bill2.Years[1] Bill2.Years[2] I can always forget the datasource, and write each cell manually, as the MSFlexGrid used to like, but if possible, I would like to use the binding capabilities of the DataGridView. Any ideas? Thanks a lot.

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• Display shift when adding rows to UITableView

  - by Kamchatka

  Hello, I have a UITableView displaying an underlying NSFetchedResultsController. When the fetchedResultsController is updated, - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { is called. And the following is executed: case NSFetchedResultsChangeInsert: [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:shiftedIndexPath] withRowAnimation:UITableViewRowAnimationFade]; break; The cellForRowAtIndexPath is only called for the new line (which is logical) The problem is however that all the values displayed in the rows of the table view are shifted down. The first row displays its title. The second rows displays the first row's title. The third row the second row's title etc. If I repeat that, the third row will display the second's row title, the fourth the third row's title etc. I don't understand what can happen, especially because cellForRowAtIndexPath is only called for the new line (which is logical) and not for all these lines. Additionally, if I click on these lines which have the wrong title, it opens the right document (didSelectRowAtIndexPath works correctly with the indexPath) Any clue of what could happen? Thanks!

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• Delete Duplicate records from large csv file C# .Net

  - by Sandhurst

  I have created a solution which read a large csv file currently 20-30 mb in size, I have tried to delete the duplicate rows based on certain column values that the user chooses at run time using the usual technique of finding duplicate rows but its so slow that it seems the program is not working at all. What other technique can be applied to remove duplicate records from a csv file Here's the code, definitely I am doing something wrong DataTable dtCSV = ReadCsv(file, columns); //columns is a list of string List column DataTable dt=RemoveDuplicateRecords(dtCSV, columns); private DataTable RemoveDuplicateRecords(DataTable dtCSV, List<string> columns) { DataView dv = dtCSV.DefaultView; string RowFilter=string.Empty; if(dt==null) dt = dv.ToTable().Clone(); DataRow row = dtCSV.Rows[0]; foreach (DataRow row in dtCSV.Rows) { try { RowFilter = string.Empty; foreach (string column in columns) { string col = column; RowFilter += "[" + col + "]" + "='" + row[col].ToString().Replace("'","''") + "' and "; } RowFilter = RowFilter.Substring(0, RowFilter.Length - 4); dv.RowFilter = RowFilter; DataRow dr = dt.NewRow(); bool result = RowExists(dt, RowFilter); if (!result) { dr.ItemArray = dv.ToTable().Rows[0].ItemArray; dt.Rows.Add(dr); } } catch (Exception ex) { } } return dt; }

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• Improve performance of searching JSON object with jQuery

  - by cale_b

  Please forgive me if this is answered on SO somewhere already. I've searched, and it seems as though this is a fairly specific case. Here's an example of the JSON (NOTE: this is very stripped down - this is dynamically loaded, and currently there are 126 records): var layout = { "2":[{"id":"40","attribute_id":"2","option_id":null,"design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"41","attribute_id":"2","option_id":"115","design_attribute_id":"4","design_option_id":"131","width":"2","height":"1", "repeat":"0","top":"0","left":"0","bottom":"4","right":"2","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"44","attribute_id":"2","option_id":"118","design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}], "5":[{"id":"326","attribute_id":"5","option_id":null,"design_attribute_id":"4","design_option_id":"154","width":"5","height":"5", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}] }; I need to match the right combination of values. Here's the function I currently use: function drawOption(attid, optid) { var attlayout = layout[attid]; $.each(attlayout, function(k, v) { // d_opt_id and d_opt_id are global scoped variable set elsewhere if (v.design_attribute_id == d_att_id && v.design_option_id == d_opt_id && v.attribute_id == attid && ((v.apply_to_options == 1 || (v.option_id === optid)))) { // Do stuff here } }); } The issue is that I might iterate through 10-15 layouts (unique attid's), and any given layout (attid) might have as many as 50 possibilities, which means that this loop is being run A LOT. Given the multiple criteria that have to be matched, would an AJAX call work better? (This JSON is dynamically created via PHP, so I could craft a PHP function that could possibly do this more efficently), or am I completely missing something about how to find items in a JSON object? As always, any suggestions for improving the code are welcome! EDIT: I apologize for not making this clear, but the purpose of this question is to find a way to improve the performance. The page has a lot of javascript, and this is a location where I know that performance is lower than it could be.

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• How can I work around the fact that in C++, sin(M_PI) is not 0?

  - by Adam Doyle

  In C++, const double Pi = 3.14159265; cout << sin(Pi); // displays: 3.58979e-009 it SHOULD display the number zero I understand this is because Pi is being approximated, but is there any way I can have a value of Pi hardcoded into my program that will return 0 for sin(Pi)? (a different constant maybe?) In case you're wondering what I'm trying to do: I'm converting polar to rectangular, and while there are some printf() tricks I can do to print it as "0.00", it still doesn't consistently return decent values (in some cases I get "-0.00") The lines that require sin and cosine are: x = r*sin(theta); y = r*cos(theta); BTW: My Rectangular - Polar is working fine... it's just the Polar - Rectangular Thanks! edit: I'm looking for a workaround so that I can print sin(some multiple of Pi) as a nice round number to the console (ideally without a thousand if-statements) edit: In case anyone's curious, this was what I landed on: double sin2(double theta) // in degrees { double s = sin(toRadians(theta)); if (fabs(s - (int)s) < 0.000001) { return floor(s + 0.5); } return s; } where toRadians() is a macro that converts to radians

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• Android maps out of memory error

  - by SamB09

  Hi , sometimes when running a google maps program with an overlay image i will receive a bit map out of memory error. It always seems to be at a random point in the app. Im not sure how to solve this. Anyone have any ideas ? My overlay code is below , im not sure if you need to see the class its called in though? public class MyOverlay2 extends Overlay { private static final double MAX_TAP_DISTANCE_KM = 3; // Rough approximation - one degree = 50 nautical miles private static final double MAX_TAP_DISTANCE_DEGREES = MAX_TAP_DISTANCE_KM * 0.5399568 * 50; private final GeoPoint gPoint; private final Context cont; private final int draw; // private final int lat; public MyOverlay2(Context cont, GeoPoint gPoint1, int draw) { // constructor will be called in the userLocation class to draw an overly image this.cont = cont; this.gPoint = gPoint1; this.draw = draw; } @Override public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) { // constructor takes 3 arguments super.draw(canvas, mapView, shadow); // Convert geo coordinates to screen pixels Point screenPoint = new Point(); mapView.getProjection().toPixels(gPoint, screenPoint); //Read the image from the xml resource using a bitmap factory BitmapFactory.Options options=new BitmapFactory.Options(); options.inSampleSize = 1; Bitmap preview_bitmap=BitmapFactory.decodeResource(cont.getResources(),R.drawable.monday12,options); //draw the image at the location specified by the co-ordinates canvas.drawBitmap(preview_bitmap, screenPoint.x - preview_bitmap.getWidth() /2, screenPoint.y - preview_bitmap.getHeight()/2 , null); // get the images height and width values divided by two draw the image at the specified screen points return true; } @Override public boolean onTap(GeoPoint s, MapView mapView) { // Handle tapping on the overlay here return true; } }

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• How to parse a custom XML-style error code response from a website

  - by user1870127

  I'm developing a program that queries and prints out open data from the local transit authority, which is returned in the form of an XML response. Normally, when there are buses scheduled to run in the next few hours (and in other typical situations), the XML response generated by the page is handled correctly by the java.net.URLConnection.getInputStream() function, and I am able to print the individual results afterwards. The problem is when the buses are NOT running, or when some other problem with my queries develops after it is sent to the transit authority's web server. When the authority developed their service, they came up with their own unique error response codes, which are also sent as XMLs. For example, one of these error messages might look like this: <Error xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <Code>3005</Code> <Message>Sorry, no stop estimates found for given values.</Message> </Error> (This code and similar is all that I receive from the transit authority in such situations.) However, it appears that URLConnection.getInputStream() and some of its siblings are unable to interpret this custom code as a "valid" response that I can handle and print out as an error message. Instead, they give me a more generic HTTP/1.1 404 Not Found error. This problem cascades into my program which then prints out a java.io.FileNotFoundException error pointing to the offending input stream. My question is therefore two-fold: 1. Is there a way to retrieve, parse, and print a custom XML-formatted error code sent by a web service using the plugins that are available in Java? 2. If the above is not possible, what other tools should I use or develop to handle such custom codes as described?

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• Best practice for writing ARRAYS

  - by Douglas

  I've got an array with about 250 entries in it, each their own array of values. Each entry is a point on a map, and each array holds info for: name, another array for points this point can connect to, latitude, longitude, short for of name, a boolean, and another boolean The array has been written by another developer in my team, and he has written it as such: names[0]=new Array; names[0][0]="Campus Ice Centre"; names[0][1]= new Array(0,1,2); names[0][2]=43.95081811364498; names[0][3]=-78.89848709106445; names[0][4]="CIC"; names[0][5]=false; names[0][6]=false; names[1]=new Array; names[1][0]="Shagwell's"; names[1][1]= new Array(0,1); names[1][2]=43.95090307839151; names[1][3]=-78.89815986156464; names[1][4]="shg"; names[1][5]=false; names[1][6]=false; Where I would probably have personally written it like this: var names = [] names[0] = new Array("Campus Ice Centre", new Array[0,1,2], 43.95081811364498, -78.89848709106445, "CIC", false, false); names[1] = new Array("Shagwell's", new Array[0,1], 43.95090307839151, -78.89815986156464, 'shg", false, false); They both work perfectly fine of course, but what I'm wondering is: 1) does one take longer than the other to actually process? 2) am I incorrect in assuming there is a benefit to the compactness of my version of the same thing? I'm just a little worried about his 3000 lines of code versus my 3-400 to get the same result. Thanks in advance for any guidance.

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• Question about creating device-compatible bitmaps in C#

  - by MusiGenesis

  I am storing bitmap-like data in a two-dimensional int array. To convert this array into a GDI-compatible bitmap (for use with BitBlt), I am using this function: public IntPtr GetGDIBitmap(int[,] data) { int w = data.GetLength(0); int h = data.GetLength(1); IntPtr ret = IntPtr.Zero; using (Bitmap bmp = new Bitmap(w, h)) { for (int x = 0; x < w; x++) { for (int y = 0; y < h; y++) { Color color = Color.FromArgb(data[x, y]); bmp.SetPixel(x, y, color); } } ret = bmp.GetHbitmap(); } return ret; } This works as expected, but the call to bmp.GetHbitmap() has to allocate memory for the returned bitmap. I'd like to modify this method in two (probably related) ways: I'd like to remove the intermediate Bitmap from the above code entirely, and go directly from my int[,] array to the device-compatible bitmap (i.e. the IntPtr). I presume this would involve calling CreateCompatibleBitmap, but I don't know how to go from that call to actually manipulating the pixel values. This should logically follow from the answer to the first, but I'd also like my method to re-use existing GDI bitmap handles (instead of creating a new bitmap each time). How can I do this? NOTE: I don't really use Bitmap.SetPixel(), as its performance could best be described as "glacial". The code is just for illustration.

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• F# and statically checked union cases

  - by Johan Jonasson

  Soon me and my brother-in-arms Joel will release version 0.9 of Wing Beats. It's an internal DSL written in F#. With it you can generate XHTML. One of the sources of inspiration have been the XHTML.M module of the Ocsigen framework. I'm not used to the OCaml syntax, but I do understand XHTML.M somehow statically check if attributes and children of an element are of valid types. We have not been able to statically check the same thing in F#, and now I wonder if someone have any idea of how to do it? My first naive approach was to represent each element type in XHTML as a union case. But unfortunately you cannot statically restrict which cases are valid as parameter values, as in XHTML.M. Then I tried to use interfaces (each element type implements an interface for each valid parent) and type constraints, but I didn't manage to make it work without the use of explicit casting in a way that made the solution cumbersome to use. And it didn't feel like an elegant solution anyway. Today I've been looking at Code Contracts, but it seems to be incompatible with F# Interactive. When I hit alt + enter it freezes. Just to make my question clearer. Here is a super simple artificial example of the same problem: type Letter = | Vowel of string | Consonant of string let writeVowel = function | Vowel str -> sprintf "%s is a vowel" str I want writeVowel to only accept Vowels statically, and not as above, check it at runtime. How can we accomplish this? Does anyone have any idea? There must be a clever way of doing it. If not with union cases, maybe with interfaces? I've struggled with this, but am trapped in the box and can't think outside of it.

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• How to access a superclass's class attributes in Python?

  - by Brecht Machiels

  Have a look at the following code: class A(object): defaults = {'a': 1} def __getattr__(self, name): print('A.__getattr__') return self.get_default(name) @classmethod def get_default(cls, name): # some debug output print('A.get_default({}) - {}'.format(name, cls)) try: print(super(cls, cls).defaults) # as expected except AttributeError: #except for the base object class, of course pass # the actual function body try: return cls.defaults[name] except KeyError: return super(cls, cls).get_default(name) # infinite recursion #return cls.__mro__[1].get_default(name) # this works, though class B(A): defaults = {'b': 2} class C(B): defaults = {'c': 3} c = C() print('c.a =', c.a) I have a hierarchy of classes each with its own dictionary containing some default values. If an instance of a class doesn't have a particular attribute, a default value for it should be returned instead. If no default value for the attribute is contained in the current class's defaults dictionary, the superclass's defaults dictionary should be searched. I'm trying to implement this using the recursive class method get_default. The program gets stuck in an infinite recursion, unfortunately. My understanding of super() is obviously lacking. By accessing __mro__, I can get it to work properly though, but I'm not sure this is a proper solution. I have the feeling the answer is somewhere in this article, but I haven't been able to find it yet. Perhaps I need to resort to using a metaclass?

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