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• Handling large (object) datasets with PHP

  - by Aron Rotteveel

  I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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• Casting pointer to object to void * in C++

  - by JB

  I've been reading StackOverflow too much and started doubting all the code I've ever written, I keep thinking "Is that undefined behavour?" even in code that has been working for ages. So my question - Is it safe and well defined behavour to cast a pointer to an object (In this case abstract interface classes) to a void* and then later on cast them back to the original class and call method using them? I'm fully aware that the code that does this is probably awful. I wouldn't even consider writing it like this now (this is old code which I don't really want to change), so I'm not looking for a discussion of better ways to do this. I already know how to write it better if I ever did this again. But if it's actually broken to rely on this in C++ then I'll have to look at changing the code, if it's merely awful code then changing it won't be a priority. I would have had no doubts about something this simple a year or two ago but as my understanding of C++ increases I actually find I have more and more worries about code being safe under the standards even if it works perfectly well. Perhaps reading too much stack overflow is a bad thing for productivity sometimes :P

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• WPF bound object update notification

  - by Carlo

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

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• Time complexity of a powerset generating function

  - by Lirik

  I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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• Is this a safe PHP mail function?

  - by Eystein

  I've finally got this PHP email script working (didn't work on localhost…), but my concern is that it's not safe. So - is this safe for spamming and any other security pitfalls I'm not aware of? <?php $email = '[email protected]'; $subject = 'Notify about stuff'; $notify = $_REQUEST['email']; if (!preg_match("/\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*/", $notify)) { echo "<h4>Your email address doesn't validate, please check that you typed it correct.</h4>"; echo "<a href='javascript:history.back(1);'>Back</a>"; } elseif(mail($email, $subject, $notify)) { echo "<h4>Thank you, you will be notified.</h4>"; } else { echo "<h4>Sorry, your email didn't get registered.</h4>"; } ?> Unrelated: is there a PHP function I can use instead of javascript:history.back(1) ?

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• NSMutableArray for Object which has NSString property causes memory leak

  - by user262325

  Hello everyone I hope to add objects to a NSMutableArray "myArray", The NSMutableArray is the array for FileObj which has a NSString property "fileName" #import <UIKit/UIKit.h> @interface FileObj : NSObject { NSString *fileName; } -(void) setfileName:(NSString *)s ; -(NSString *) getfileName ; @end // // File.m// #import "File.h" @implementation FileObj -(void) setfileName:(NSString *)s ; { fileName=s; } -(NSString *) getfileName ; { return fileName; } @end I initialize the myArray here: NSMutableArray *temarray; temarray=[[NSMutableArray alloc] init]; self.myArray=temarray; [temarray release]; the codes to add object to myArray FileObj *newobj=[[FileObj alloc]init ]; NSString *fieldValue2 = [[NSString alloc] initWithUTF8String:@"aaaa"]; [newobj setfileName:fieldValue2]; [myArray addObject:newobj]; [fieldValue2 release]; //**if I enabled the line, it will cause crash** //**if I disable the line, it will cause memory leak** [newobj release]; Welcome any comment Thanks interdev

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• Function to even out multiple arrays

  - by Moak

  Assume I have a function evenOut($array, $limit){ //returns exactly $limit items } and this data $animals = array(); $animals['barn'] = array_fill(0,20, 'b'); $animals['forest'] = array_fill(0,20, 'f'); $animals['house'] = array_fill(0,20, 'h'); $animals['mountain'] = array_fill(0,20, 'm'); I want to return a maximum of 10 animals, however they should be spread out evenly among the locations they come from. so if i did evenOut($animals,8); i'd get 2 of each('b','b','f','f','h','h','m','m',) evenOut($animals,2); should return ('b','f') if I have this data $animals = array(); $animals['barn'] = array_fill(0,1, 'b'); $animals['forest'] = array_fill(0,3, 'f'); $animals['house'] = array_fill(0,8, 'h'); $animals['mountain'] = array_fill(0,1, 'm'); evenOut($animals,8); expected result would be ('b','f','f','f','h','h','h','m',) evenOut($animals,10); expected result would be ('b','f','f','f','h','h','h','h','h','m',) $animals = array(); $animals['barn'] = array_fill(0,0, 'b'); $animals['forest'] = array_fill(0,3, 'f'); evenOut($animals,10); expected result would be ('f','f','f') I'm not sure how I should approach this, I am hoping there is a simple way

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• Nhibernate Cannot delete the child object

  - by Daoming Yang

  I know it has been asked for many times, i also have found a lot of answers on this website, but i just cannot get out this problem. Can anyone help me with this piece of code? Many thanks. Here is my parent mapping file <set name="ProductPictureList" table="[ProductPicture]" lazy="true" order-by="DateCreated" inverse="true" cascade="all-delete-orphan" > <key column="ProductID"/> <one-to-many class="ProductPicture"/> </set> Here is my child mapping file <class name="ProductPicture" table="[ProductPicture]" lazy="true"> <id name="ProductPictureID"> <generator class="identity" /> </id> <property name="ProductID" type="Int32"></property> <property name="PictureName" type="String"></property> <property name="DateCreated" type="DateTime"></property> </class> Here is my c# code var item = _productRepository.Get(productID); var productPictrue = item.ProductPictureList .OfType<ProductPicture>() .Where(x => x.ProductPictureID == productPictureID); // reomve the finding item var ok = item.ProductPictureList.Remove(productPictrue); _productRepository.SaveOrUpdate(item); ok is false value and this child object is still in my database.

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• Image Gurus: Optimize my Python PNG transparency function

  - by ozone

  I need to replace all the white(ish) pixels in a PNG image with alpha transparency. I'm using Python in AppEngine and so do not have access to libraries like PIL, imagemagick etc. AppEngine does have an image library, but is pitched mainly at image resizing. I found the excellent little pyPNG module and managed to knock up a little function that does what I need: make_transparent.py pseudo-code for the main loop would be something like: for each pixel: if pixel looks "quite white": set pixel values to transparent otherwise: keep existing pixel values and (assuming 8bit values) "quite white" would be: where each r,g,b value is greater than "240" AND each r,g,b value is within "20" of each other This is the first time I've worked with raw pixel data in this way, and although works, it also performs extremely poorly. It seems like there must be a more efficient way of processing the data without iterating over each pixel in this manner? (Matrices?) I was hoping someone with more experience in dealing with these things might be able to point out some of my more obvious mistakes/improvements in my algorithm. Thanks!

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• UIImage Object surprisingly returning null but not NSData

  - by riyaz

  i have created a sqlite db. and i have insert a few datas in my db.. UIImage * imagee=[UIImage imageNamed:@"image.png"]; NSData *mydata=[NSData dataWithData:UIImagePNGRepresentation(imagee)]; const char *dbpath = [databasePath UTF8String]; NSString *insertSQL=[NSString stringWithFormat:@"insert into CONTACTS values(\"%@\",\"%@\")",@"Mathan",mydata]; NSLog(@"mydata %@",mydata); sqlite3_stmt *addStatement; const char *insert_stmt=[insertSQL UTF8String]; if (sqlite3_open(dbpath,&contactDB)==SQLITE_OK) { sqlite3_prepare_v2(contactDB,insert_stmt,-1,&addStatement,NULL); if (sqlite3_step(addStatement)==SQLITE_DONE) { sqlite3_bind_blob(addStatement,1, [mydata bytes], [mydata length], SQLITE_TRANSIENT); NSLog(@"Data saved"); } else{ NSLog(@"Some Error occured"); } sqlite3_close(contactDB); } else{ NSLog(@"Failure"); } have written some codes to retrive the data sqlite3_stmt *statement; if (sqlite3_open([databasePath UTF8String], &contactDB) == SQLITE_OK) { NSString *sql = [NSString stringWithFormat:@"SELECT * FROM contacts"]; if (sqlite3_prepare_v2( contactDB, [sql UTF8String], -1, &statement, nil) == SQLITE_OK) { while (sqlite3_step(statement) == SQLITE_ROW) { char *field1 = (char *) sqlite3_column_text(statement, 0); NSString *field1Str = [[NSString alloc] initWithUTF8String: field1]; NSLog(@"UserName %@",field1Str); NSData *data = [[NSData alloc] initWithBytes:sqlite3_column_blob(statement, 1) length:sqlite3_column_bytes(statement, 1)]; UIImage *newImage = [[UIImage alloc]initWithData:data]; NSLog(@"Image OBJ %@",newImage); NSLog(@"Image Data %@",data); } sqlite3_close(contactDB); } } sqlite3_finalize(statement); the problem is in log, inserted NSData object and retrieved NSData Objects are different (printing in log gives different stream) moreover Image OBJ is printed null in log.. Have seen similar questions in stackoverflow. But nothing seems to help. Please give some suggestions to overcome this issue.

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• php lampp permissions of fopen function

  - by marmoushismail

  hi i'm programming php using: netbeans 6.8 lampp for ubuntu (xampp) apache which came with xampp $fh = fopen("testfile2.txt", 'w') or die("Failed to create file"); $text ="hello man cool good"; fwrite($fh, $text) or die("Could not write to file"); fclose($fh); echo "File 'testfile.txt' written successfully"; //i get the next error: Warning: fopen(testfile2.txt) [function.fopen]: failed to open stream: Permission denied in /home/marmoush/allprojects/phpprojects/myindex.php on line 91 Failed to create file anyway i know what this error is; it's about folder and files permissions; i looked into the folder permission tab made access available for "others" group ( to read and write) the program worked result was a file (test.txt) so i looked at the created file permission it appears to be that (php , xampp or whoever) creates file with (nobody permission) I have 2 QUESTIONS: 1- what if i need the file created by (php code and xampp ) to have the "root or user or myname" permissions ?? where to set this setting 2-also my concern (what if i send this files to actual web server will it make nobody permissions also nobody ? when they create files

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• Memory Management with returning char* function

  - by RageD

  Hello all, Today, without much thought, I wrote a simple function return to a char* based on a switch statement of given enum values. This, however, made me wonder how I could release that memory. What I did was something like this: char* func() { char* retval = new char; // Switch blah blah - will always return some value other than NULL since default: return retval; } I apologize if this is a naive question, but what is the best way to release the memory seeing as I cannot delete the memory after the return and, obviously, if I delete it before, I won't have a returned value. What I was thinking as a viable solution was something like this void func(char*& in) { // blah blah switch make it do something } int main() { char* val = new char; func(val); // Do whatever with func (normally func within a data structure with specific enum set so could run multiple times to change output) val = NULL; delete val; val = NULL; return 0; } Would anyone have anymore insight on this and/or explanation on which to use? Regards, Dennis M.

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• Typedef equivalence in function arguments

  - by Warren Seine

  Hi guys, The question is kind of hard to ask without an example so here it is: #include <vector> struct O { }; struct C { template <typename T> void function1(void (C::*callback)(const O*)); template <typename T> void function2(void (C::*callback)(const typename T::value_type)); void print(const O*); }; int main() { C c; c.function1< std::vector<O*> >(&C::print); // Success. c.function2< std::vector<O*> >(&C::print); // Fail. } The error that I am given is: error: no matching function for call to ‘C::function2(void (C::*)(const O*))’. Basically, the only difference between calls is that in function2, I'm more generic since I use the typedef std::vector<O*>::value_type which should resolve to O*, hence similar to function1. I'm using G++ 4.2.1 (I know it's old), but Comeau confirms I'm wrong. Why does the compilation fail?

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• Elements of a Java Object Array are created but without correct names

  - by Greenhouse Gases

  Hi all Im having rather an annoying problem. I have a class called Person and a class called Event which serve to create objects to be used for competitors that compete in a certain event. When I add a competitor thats fine and the GUI list updates accordingly, however when I add an event the element in the array does not take on the value of the instance variable name in the class Event and so the GUI does not show the event name, though it is being added in the array correctly. How can I make it so that the event object in each element of the listOfEvents array (which is an array of event objects) has the name of the event. I should add this is for university though this isnt the part for which we will be assessed, it is somethign i have come across and due to not being able to see the code for the GUI, I've hit the proverbial brick wall. I wont include the whole load of code Ive been writing but hopefully my description and snippets below will suffice. Any advice I would appreciate greatly. No doubt I have overlooked something simple! Many thanks. listOfEvents is declared as: Event[] listOfEvents = new Event[20]; A snippet from the Event class: public class Event { String name; Person[] participants = new Person[10]; // array of competitors for the event public Event(String name) { this.name = name; } } and its use in the addEvent method (p is a global variable): public void addEvent(String eventName) { listOfEvents[p] = new Event(eventName); p++; }

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• linked list sort function only loops once

  - by Tristan Pearce

  i have a singly linked list that i am trying to sort from least to greatest by price. here is what i have so far struct part { char* name; float price; int quantity; struct part *next; }; typedef struct part partType; partType *sort_price(partType **item) { partType *temp1 = *item; partType *temp2 = (*item)->next; if ( *item == NULL || (*item)->next == NULL ) return *item; else { while ( temp2 != NULL && temp2->next != NULL ){ if (temp2->price > temp2->next->price){ temp1->next = temp2->next; temp2->next = temp2->next->next; temp1->next->next = temp2; } temp1 = temp2; temp2 = temp2->next; } } return *item; } the list is already populated but when i call the sort function it only swaps the first two nodes that satisfy the condition in the if statement. I dont understand why it doesnt do the check again after the two temp pointers are incremented.

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• C++ string.substr() function problem

  - by VaioIsBorn

  I want to make a program that will read some number in string format and output it like this: if the number is 12345 it should then output 12 23 34 45 . I tried using the substr() function from the c++ string library, but it gives me strange results - it outputs 1 23 345 45 instead of the expected result. Why ? #include <iostream> #include <string> #include <cstdlib> using namespace std; int main(void) { string a;cin >> a; string b;int c; for(int i=0;i<a.size()-1;++i) { b = a.substr(i,i+1); c = atoi(b.c_str()); cout << c << " "; } cout << endl; return 0; }

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• MySQL updating a field to result of a function

  - by jdborg

  mysql> CREATE FUNCTION test () -> RETURNS CHAR(16) -> NOT DETERMINISTIC -> BEGIN -> RETURN 'IWantThisText'; -> END$$ Query OK, 0 rows affected (0.00 sec) mysql> SELECT test(); +------------------+ | test() | +------------------+ | IWantThisText | +------------------+ 1 row in set (0.00 sec) mysql> UPDATE `table` -> SET field = test() -> WHERE id = 1 Query OK, 1 row affected, 1 warning (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 1 mysql> SHOW WARNINGS; +---------+------+----------------------------------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------------------------------+ | Warning | 1265 | Data truncated for column 'test' at row 1 | +---------+------+----------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT field FROM table WHERE id = 1; +------------------+ | field | +------------------+ | NULL | +------------------+ 1 row in set (0.00 sec) What I am doing wrong? I just want field to be set to the returned value of test() Forgot to mention field is VARCHR(255)

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• Declaring an object of a conditional type with a System.Type

  - by Chapso

  I am attempting to launch a specific form depending on the selected node of a treeview on the doubleclick event. The code I need to use to launch the form is a little bulky becuase I have to ensure that the form is not disposed, and that the form is not already open, before launching a new instance. I'd like to have all of this checking happen in one place at the end of the function, which means that I have to be able to pass the right form type to the code at the end. I'm trying to do this with a System.Type, but that doesn't seem to be working. Could someone point me in the right direction, please? With TreeView.SelectedNode Dim formType As Type Select Case .Text Case "Email to VPs" formType = EmailForm.GetType() Case "Revise Replacers" formType = DedicatedReplacerForm.GetType() Case "Start Email" formType = EmailForm.GetType() End Select Dim form As formType Dim form As formType Try form = CType(.Tag, formType) If Not form.IsDisposed Then form.Activate() Exit Sub End If Catch ex As NullReferenceException 'This will error out the first time it is run as the form has not yet ' been defined. End Try form = New formType form.MdiParent = Me .Tag = form CType(TreeView.SelectedNode.Tag, Form).Show() End With

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• Design Pattern for Changing Object

  - by user210757

  Is there a Design Pattern for supporting different permutations object? Version 1 public class myOjbect { public string field1 { get; set; } /* requirements: max length 20 */ public int field2 { get; set; } . . . public decimal field200 { get; set; } } Version 2 public class myObject { public string field1 { get; set; } /* requirements: max length 40 */ public int field2 { get; set; } . . . public double field200 { get; set; } /* changed data types */ . . ./* 10 new properties */ public double field210 { get; set; } } of course I could just have separate objects, but thought there might be a good pattern for this sort of thing.

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• Fatal error: Call to a member function escape() on a non-object in .....on line 10

  - by danyo

  i am making a simple javascript login form for wordpress. i have the form submitting to the following bit of php to handle the login: <?php get_header(); global $user_ID; if (!$user_ID) { if($_POST){ //We shall SQL escape all inputs $username = $wpdb->escape($_REQUEST['username']); $password = $wpdb->escape($_REQUEST['password']); $remember = $wpdb->escape($_REQUEST['rememberme']); if($remember) $remember = "true"; else $remember = "false"; $login_data = array(); $login_data['user_login'] = $username; $login_data['user_password'] = $password; $login_data['remember'] = $remember; $user_verify = wp_signon( $login_data, false ); //wp_signon is a wordpress function which authenticates a user. It accepts user info parameters as an array. if ( is_wp_error($user_verify) ) { echo "<span class='error'>Invalid username or password. Please try again!</span>"; exit(); } else { echo "<script type='text/javascript'>window.location='". get_bloginfo('url') ."'</script>"; exit(); } } else { //get_header(); ?> any ideas on why i am getting the error? Cheers, Dan

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• object references an unsaved transient instance

  - by developer

  Hi, I have 2 tables, user and userprofile, both with almost identical fields. user table references userprofile table by primary key ID. My requirement is that on click of a button I need to dump user table record to userprofile table. Now for a particular user table, if there is a corresponding userprofile entry, I am successfully able to dump the data, but if there is no record in userprofile table then I need to create a new record by dumping all the data. My problem is that I am able to update the data when the record is present in userprofile table, but in the case wherein I have to create a new record I get the below error "object references an unsaved transient instance - save the transient instance before flushing". `<class name="User"> <id name="ID" type="Int32"> <generator class="native" /> </id> <many-to-one name="Pid" class="UserProfile" /> </class>` UserProfile is another table and Pid above references the Primary key ID of UserProfile table.

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• Stored procedure or function expects parameter which is not supplied

  - by user2920046

  I am trying to insert data into a SQL Server database by calling a stored procedure, but I am getting the error Procedure or function 'SHOWuser' expects parameter '@userID', which was not supplied. My stored procedure is called "SHOWuser". I have checked it thoroughly and no parameters is missing. My code is: public void SHOWuser(string userName, string password, string emailAddress, List preferences) { SqlConnection dbcon = new SqlConnection(conn); try { SqlCommand cmd = new SqlCommand(); cmd.Connection = dbcon; cmd.CommandType = System.Data.CommandType.StoredProcedure; cmd.CommandText = "SHOWuser"; cmd.Parameters.AddWithValue("@userName", userName); cmd.Parameters.AddWithValue("@password", password); cmd.Parameters.AddWithValue("@emailAddress", emailAddress); dbcon.Open(); int i = Convert.ToInt32(cmd.ExecuteScalar()); cmd.Parameters.Clear(); cmd.CommandText = "tbl_pref"; foreach (int preference in preferences) { cmd.Parameters.Clear(); cmd.Parameters.AddWithValue("@userID", Convert.ToInt32(i)); cmd.Parameters.AddWithValue("@preferenceID", Convert.ToInt32(preference)); cmd.ExecuteNonQuery(); } } catch (Exception) { throw; } finally { dbcon.Close(); } and the stored procedure is: ALTER PROCEDURE [dbo].[SHOWuser] -- Add the parameters for the stored procedure here ( @userName varchar(50), @password nvarchar(50), @emailAddress nvarchar(50) ) AS BEGIN INSERT INTO tbl_user(userName,password,emailAddress) values(@userName,@password,@emailAddress) select tbl_user.userID,tbl_user.userName,tbl_user.password,tbl_user.emailAddress, stuff((select ',' + preferenceName from tbl_pref_master inner join tbl_preferences on tbl_pref_master.preferenceID = tbl_preferences.preferenceID where tbl_preferences.userID=tbl_user.userID FOR XML PATH ('')),1,1,' ' ) AS Preferences from tbl_user SELECT SCOPE_IDENTITY(); END Pls help, Thankx in advance...

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• Creating a sort function for a generic list

  - by Andrey

  I have a method for sorting generic lists by the object fields: public static IQueryable<T> SortTable<T>(IQueryable<T> q, string sortfield, bool ascending) { var p = Expression.Parameter(typeof(T), "p"); if (typeof(T).GetProperty(sortfield).PropertyType == typeof(int?)) { var x = Expression.Lambda<Func<T, int?>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } else if (typeof(T).GetProperty(sortfield).PropertyType == typeof(int)) { var x = Expression.Lambda<Func<T, int>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } else if (typeof(T).GetProperty(sortfield).PropertyType == typeof(DateTime)) { var x = Expression.Lambda<Func<T, DateTime>>(Expression.Property(p, sortfield), p); if (ascending) q = q.OrderBy(x); else q = q.OrderByDescending(x); } // many more for every type return q; } Is there any way I can collapse those ifs to a single generic statement? The main problem is that for the part Expression.Lambda<Func<T, int>> I am not sure how to write it generically.

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• Copy object using pointer (templates)

  - by Azodious

  How the push_back of stl::vector is implemented so it can make copy of any datatype .. may be pointer, double pointer and so on ... I'm implementing a template class having a function push_back almost similar to vector. Within this method a copy of argument should be inserted in internal memory allocated memory. but the argument is a pointer. (an object pointer). Can you pls tell how to create copy from pointer. so that if i delete the pointer in caller still the copy exists in my template class? Code base is as follows: template<typename T> class Vector { public: void push_back(const T& val_in) { T* a = *(new T(val_in)); m_pData[SIZE++] = a; } } Caller: Vector<MyClass*> v(3); MyClass* a = new MyClass(); a->a = 0; a->b = .5; v.push_back(a); delete a; Thanks.

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• Problem using find function in Matlab

  - by Peter Etchells

  Hi all, I have two arrays of data that I'm trying to amalgamate. One contains actual latencies from an experiment in the first column (e.g. 0.345, 0.455... never more than 3 decimal places), along with other data from that experiment. The other contains what is effectively a 'look up' list of latencies ranging from 0.001 to 0.500 in 0.001 increments, along with other pieces of data. Both data sets are X-by-Y doubles. What I'm trying to do is something like... for i = 1:length(actual_latency) row = find(predicted_data(:,1) == actual_latency(i) full_set(i,1:4) = [actual_latency(i) other_info(i) predicted_info(row,2)... predicted_info(row,3)]; end ...in order to find the relevant row in predicted_data where the look up latency corresponds to the actual latency. I then use this to created an amalgamated data set, full_set. I figured this would be really simple, but the find function keeps failing by throwing up an empty matrix when looking for an actual latency that I know is in predicted_data(:,1) (as I've double-checked during debugging). Moreover, if I replace find with a for loop to do the same job, I get a similar error. It doesn't appear to be systematic - using different participant data sets throws it up in different places. Furthermore, during debugging mode, if I use find to try and find a hard-coded value of actual_latency, it doesn't always work. Sometimes yes, sometimes no. I'm really scratching my head over this, so if anyone has any ideas about what might be going on, I'd be really grateful.

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