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  • login script in php using session variables

    - by kracekumar
    ? username: '; } else { $user=$_POST['user']; $query="select name from login where name='$user'"; $result=mysql_query($query) or die(mysql_error()); $rows=mysql_num_rows($result)or die(mysql_error()); session_start(); //echo "results"; $username=mysql_fetch_array($result) or die(mysql_error()); $fields=mysql_num_fields($result) or die(mysql_error()); echo "username:$username[0]"; $_SESSION['username']=$username[0]; $sesion_username=$_SESSION['username']; //echo "rows:$rows"." "."fields:$fields"; echo""."username:$sesion_username"; } ? i wanted to create a site where user can login and upload their details depending on their user name have stored their details in a database,the problem i am facing is two people 'a' and 'b' login one after other session_variable $_SESSION['username'] will have 'b's' username ,so i can't display 'a's' details now. . . . what i want to achieve is when a user logins in i want to store his name and other details in session variable and navigate him according and display his details

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  • Is there any way to output the actual array in c++

    - by user2511129
    So, I'm beginning C++, with a semi-adequate background of python. In python, you make a list/array like this: x = [1, 2, 3, 4, 5, 6, 7, 8, 9] Then, to print the list, with the square brackets included, all you do is: print x That would display this: [1, 2, 3, 4, 5, 6, 7, 8, 9] How would I do the exact same thing in c++, print the brackets and the elements, in an elegant/clean fashion? NOTE I don't want just the elements of the array, I want the whole array, like this: {1, 2, 3, 4, 5, 6, 7, 8, 9} When I use this code to try to print the array, this happens: input: #include <iostream> using namespace std; int main() { int anArray[9] = {1, 2, 3, 4, 5, 6, 7, 8, 9}; cout << anArray << endl; } The output is where in memory the array is stored in (I think this is so, correct me if I'm wrong): 0x28fedc As a sidenote, I don't know how to create an array with many different data types, such as integers, strings, and so on, so if someone can enlighten me, that'd be great! Thanks for answering my painstakingly obvious/noobish questions!

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  • Identifying memory leaks in C++

    - by Dororo
    I've got the following bit of code, which I've narrowed down to be causing a memory leak (that is, in Task Manager, the Private Working Set of memory increases with the same repeated input string). I understand the concepts of heaps and stacks for memory, as well as the general rules for avoiding memory leaks, but something somewhere is still going wrong: while(!quit){ char* thebuffer = new char[210]; //checked the function, it isn't creating the leak int size = FuncToObtainInputTextFromApp(thebuffer); //stored in thebuffer string bufferstring = thebuffer; int startlog = bufferstring.find("$"); int endlog = bufferstring.find("&"); string str_text=""; str_text = bufferstring.substr(startlog,endlog-startlog+1); String^ str_text_m = gcnew String(str_text_m.c_str()); //some work done delete str_text_m; delete [] thebuffer; } The only thing I can think of is it might be the creation of 'string str_text' since it never goes out of scope since it just reloops in the while? If so, how would I resolve that? Defining it outside the while loop wouldn't solve it since it'd also remain in scope then too. Any help would be greatly appreciated.

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  • XSLT; parse escaped text to a node-set and extract subelements

    - by Tom W
    Hello SO; I've been fighting with this problem all day and am just about at my wit's end. I have an XML file in which certain portions of data are stored as escaped text but are themselves well-formed XML. I want to convert the whole hierarchy in this text node to a node-set and extract the data therein. No combination of variables and functions I can think of works. The way I'd expect it to work would be: <xsl:variable name="a" select="InnerXML"> <xsl:for-each select="exsl:node-set($a)/*"> 'do something </xsl:for-each> The input element InnerXML contains text of the form <root><element a>text</element a><element b><element c/><element d>text</element d></element b></root> but that doesn't really matter. I just want to navigate the xml like a normal node-set. Where am I going wrong?

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  • Storing large json strings to database + hash

    - by Guy
    I need to store quiete large JSON data strings to the database. I am using gzip to compress the string and therefore BLOB MySQL data type to store it. However, only 5% of all the requests contain unique data and only unique data ought to be stored to the database. My approach is as follows. array_multisort data (array [a, b, c] is virtually the same as [a, c, b]). json_encode data (json_encode is faster than serialize; we need string array representation for the step 3). sha1 data (slower than md5, though less possible the collisions). Check if the hash exists in the database. 5.1 yes – do not insert the data. 5.2. no – gzip the data and store it along the hash. Is there anything about this (apart from storing JSON data to the database in the first place) that sounds fishy or should be done a different way? p.s. We are talking about a database with roughly 1kk unique records being created every month.

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  • Access php multidimensional array key based on a variable string

    - by ggirtsou
    I have stored the XML path to items in a string like this: response->items->item. What I need to do is to access an array called $xml_array like this: $xml_array['response']['items']['item'] When I write it in the code it works. The thing is that I want it to be done on the fly. I use this to convert response->items->item to ['response']['items']['item']: $xml_path = 'response->items->item'; $explode_path = explode('->', $xml_path); $correct_string = false; foreach($explode_path as $path) { $correct_string .= '[\''.$path.'\']'; } the problem is that I can't access $xml_array by doing this: $xml_array[$correct_string] So I end up with this: $xml_tag = 'title'; $xml_path = 'response->items->item'; $correct_string = '$items = $xml2array'; $explode_path = explode('->', $xml_path); foreach($explode_path as $path) { $correct_string .= '[\''.$path.'\']'; } $correct_string .= ';'; eval($correct_string); foreach($items as $item) { echo $item[$xml_tag].'<br />'; } and access the $xml_array array through $items array. Is there any way I can do this and avoid using eval()? Thanks in advance!

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  • jQuery: Triggering a click on an img not working

    - by Twecs
    I'm testing in Chrome. I have a bunch of 'add item' icons on screen that the user can click in order to add that one item to the database. I also have a button at the botton of that list, which should add the whole list of items. It seems to me that the easiest way to do this is to trigger the 'click' event for all these icons (the reason I'm doing it via the icons is that items-specific values are stored as attributes of the div in which the icon resides). However, I can't get it to work: the event handlers for the individual icons work perfectly, and the event handler for the add-them-all button does give me an alert if I put that in. But if I add the I read some posts that suggest browsers don't allow you to trigger click events, so I added a 'hover' event listener to the icons to see if the problem is in the type of event I want to trigger. Answer: no, same story: the alert will work, but the trigger won't. I have placed the icon event listener in the code before the button event listener. What's going on? Twecs

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  • Safe way for getting/finding a vertex in a graph with custom properties -> good programming practice

    - by Shadow
    Hi, I am writing a Graph-class using boost-graph-library. I use custom vertex and edge properties and a map to store/find the vertices/edges for a given property. I'm satisfied with how it works, so far. However, I have a small problem, where I'm not sure how to solve it "nicely". The class provides a method Vertex getVertex(Vertexproperties v_prop) and a method bool hasVertex(Vertexproperties v_prop) The question now is, would you judge this as good programming practice in C++? My opinion is, that I have first to check if something is available before I can get it. So, before getting a vertex with a desired property, one has to check if hasVertex() would return true for those properties. However, I would like to make getVertex() a bit more robust. ATM it will segfault when one would directly call getVertex() without prior checking if the graph has a corresponding vertex. A first idea was to return a NULL-pointer or a pointer that points past the last stored vertex. For the latter, I haven't found out how to do this. But even with this "robust" version, one would have to check for correctness after getting a vertex or one would also run into a SegFault when dereferencing that vertex-pointer for example. Therefore I am wondering if it is "ok" to let getVertex() SegFault if one does not check for availability beforehand?

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  • Maximum length of a std::basic_string<_CharT> string

    - by themoondothshine
    Hey all, I was wondering how one can fix an upper limit for the length of a string (in C++) for a given platform. I scrutinized a lot of libraries, and most of them define it arbitrarily. The GNU C++ STL (the one with experimental C++0x features) has quite a definition: size_t npos = size_t(-1); /*!< The maximum value that can be stored in a variable of type size_t */ size_t _S_max_len = ((npos - sizeof(_Rep_base))/sizeof(_CharT) - 1) / 4; /*!< Where _CharT is a template parameter; _Rep_base is a structure which encapsulates the allocated memory */ Here's how I understand the formula: The size_t type must hold the count of units allocated to the string (where each unit is of type _CharT) Theoretically, the maximum value that a variable of type size_t can take on is the total number of units of 1 byte (ie, of type char) that may be allocated The previous value minus the overhead required to keep track of the allocated memory (_Rep_base) is therefore the maximum number of units in a string. Divide this value by sizeof(_CharT) as _CharT may require more than a byte Subtract 1 from the previous value to account for a terminating character Finally, that leave the division by 4. I have absolutely no idea why! I looked at a lot of places for an explanation, but couldn't find a satisfactory one anywhere (that's why I've been trying to make up something for it! Please correct me if I'm wrong!!).

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  • How to structure Javascript programs in complex web applications?

    - by mixedpickles
    Hi there. I have a problem, which is not easily described. I'm writing a web application that makes heavy usage of jquery and ajax calls. Now I don't have experience in designing the architecture for javascript programms, but I realize that my program has not a good structure. I think I have to many identifiers referring to the same (at least more or less) thing. Let's have an exemplary look at an arbitrary UI widget: The eventhandlers use DOM elements as parameters. The DOM element represents a widget in the browser. A lot of times I use jQuery objects (I think they are basically a wrapper around DOM elements) to do something with the widget. Sometimes they are used transiently, sometimes they are stored in a variable for later purposes. The ajax function calls use strings identifiers for these widgets. They are processed server side. Beside that I have a widget class whose instances represents a widget. It is instantiated through the new operator. Now I have somehow four different object identifiers for the same thing, which needs to be kept in sync until the page is loaded anew. This seems not to be a good thing. Any advice?

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  • Problem in data binding in NSString?

    - by Rajendra Bhole
    Hi, I selecting the row of the table. The text of the row i stored in the application delegate object as a NSString. That NSString i want to retrieving or binding in SELECT statement of SQLite query, For that i written code in the TableView Class (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { selectedText = [appDelegate.categoryArray objectAtIndex:indexPath.row]; appDelegate.selectedTextOfRow = selectedText; ListOfPrayersViewController *listVC = [[ListOfPrayersViewController alloc] init]; [self.navigationController pushViewController:listVC animated:YES]; [listVC release]; } and database class class code is. + (void) getDuas:(NSString *)dbPath{ if(sqlite3_open([dbPath UTF8String], &database) == SQLITE_OK){ SalahAppDelegate *appDelegate = (SalahAppDelegate *)[[UIApplication sharedApplication] delegate]; NSString *categoryTextForQuery =[NSString stringWithFormat:@"SELECT Category FROM Prayer WHERE Category ='%s'", appDelegate.selectedTextOfRow ]; NSLog(@"The Text %@", categoryTextForQuery); //const char *sqlQuery1 = (char *)categoryTextForQuery; //const char *sqlQuery = "SELECT Category FROM Prayer WHERE Category = 'Invocations for the beginning of the prayer'"; sqlite3_stmt *selectstmt; if(sqlite3_prepare_v2(database, [categoryTextForQuery UTF8String], -1, &selectstmt, NULL) == SQLITE_OK){ appDelegate.duasArray =[[NSMutableArray alloc] init]; while(sqlite3_step(selectstmt) == SQLITE_ROW){ NSString *dua = [[NSString alloc] initWithCString:(char *)sqlite3_column_text(selectstmt,0) encoding:NSASCIIStringEncoding]; Prayer *prayerObj = [[Prayer alloc] initwithDuas:dua]; prayerObj.DuaName = dua; [appDelegate.duasArray addObject:prayerObj]; } } } } The code is comes out of loop on the statement or starting the loop of the while(sqlite3_step(selectstmt) == SQLITE_ROW) Why? How i bind the table selected text in SELECT statement of sqlite?

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  • how to fetch data from XML and update database table.

    - by ppp
    I am passing serialized collection(XML) to stored procedure. My XML structure is- <ArrayofDepartmentEntity> <Department> <id>1004</id> <budget>2500.oo</budget> </Department> <Department> <id>1080</id> <budget>3500.oo</budget> </Department> <Department> <id>1029</id> <budget>4500.00</budget> </Department> </ArrayofDepartmentEntity> How can I UPDATE corresponding budget column where department IDs are in above XML?? can any body write down the sql syntax. my SP syntax- ALTER PROCEDURE [dbo].[usp_SaveDepartentBudget] ( @departmentBudgetXML ntext = NULL ) AS BEGIN DECLARE @ptrHandle int EXEC sp_xml_preparedocument @ptrHandle OUTPUT, @departmentBudgetXML ....Here I want to update Budget foreach departmentID in @departmentBudgetXML

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  • Submitting form with Ajax

    - by Sidetracking
    So I'm completely lost on how to submit a form with Ajax. I'm fairly new to Javascript and hopefully I'm not in over my head. When I click submit on my form, nothing happens on my page, not in my SQL database where the info should be stored (double checked process form too). Here's the code if anyone's willing to help Javascript: $(document).ready(function() { $('#form').submit(function() { $.ajax({ url: "../process.php", type: "post", data: $(this).serialize() }); }); } HTML: <form name="contact" method="post" action="" id="form"> <span id="input"> <input type="text" name="first" maxlength="50" size="30" title="First Name" class="textbox"> <input type="text" name="last" maxlength="80" size="30" title="Last Name" class="textbox"> <input type="text" name="email" maxlength="80" size="30" title="Email" class="textbox"> <textarea name="request" maxlength="1000" cols="25" rows="6" title="Request"></textarea> </span> <input type="submit" value="Submit" class="submit"> </form>

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  • memcached: which is faster, doing an add (and checking result), or doing a get (and set when returni

    - by Mike Sherov
    The title of this question isn't so clear, but the code and question is straightforward. Let's say I want to show my users an ad once per day. To accomplish this, every time they visit a page on my site, I check to see if a certain memcache key has any data stored on it. If so, don't show an ad. If not, store the value '1' in that key with an expiration of 86400. I can do this 2 ways: //version a $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->get($key)===false){ $memcache->set($key,'1',false,$expire); //show ad } //version b $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->add($key,'1',false,$expire)){ //show ad } Now, it might seem obvious that b is better, it always makes 1 memcache call. However, what is the overhead of "add" vs. "get"? These aren't the real comparisons... and I just made up these numbers, but let's say 1 add ~= 1 set ~= 5 get in terms of effort, and the average user views 5 pages a day: a: (5 get * 1 effort) + (1 set * 5 effort) = 10 units of effort b: (5 add * 5 effort) = 25 units of effort Would it make sense to always do the add call? Is this an unnecessary micro-optimization?

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  • Calling a constructor to reinitialize variables doesn't seem to work?

    - by Matt
    I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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  • What is the best way to create a running integer id on the AppEngine data storage?

    - by Freed
    For various reasons, I need a unique running integer id for my entities stored on the Google AppEngine. The automatically generated key sort of has this behaviour, but it doesn't start from 1 (or 0) and doesn't guarantee that the generated integer part will come from a continuous sequence. What would be the best way to efficiently implement this on AppEngine? Is there any support from the storage system? To add to the complexity, I might need to do this over entities from different entity groups, meaning I can't just get the highest id right now and save an entity with the next id in a transaction. Might memcache be the way to go..? Edit: I havn't yet implemented this, but to clarify on the memcache idea. I know memcache is unreliable, but in practice it probably won't lose data "too often" to hurt performance. Basically, I would have a memcache entry for the last used id, update it (somehow atomically) whenever I create a new entity and use that id. In the case of memcache not having a value for this entry, I'd get the highest id so far by doing a query on my entities sorted by the id and update memcache (unless someone else had already done so). The only problem I can see with this right now would be atomicity of the operation as a whole if the save of my new entity was also part of a transaction. Thoughts..?

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  • Best method to cache objects in PHP?

    - by Martin Bean
    Hi, I'm currently developing a large site that handles user registrations. A social networking website for argument's sake. However, I've noticed a lag in page loads and deciphered that it is the creation of objects on pages that's slowing things down. For example, I have a Member object, that when instantiated with an ID passed as a construct parameter, it queries the database for that members' row in the members database table. Not bad, but this is created each time a page is loaded; and called more than once when say, calling an array of that particular members' friends, as a new Member object is created for each friend. So on a single page I can have upwards of seven of the same object, but containing different properties. What I'm wanting to do is to find a way to reduce the database load, and to allow persist objects between page loads. For example, the logged in user's object to be created on login (which I can do) but then stored somewhere for retrieval so I don't have to keep re-creating the object between page loads. What is the best solution for this? I've had a look at Memcache, but with it being a third-party module I can't have the web host install it on this occasion. What are my alternatives, and/or best practices in my case? Thanks in advance.

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  • new project app; use entirely node.js

    - by Jared
    I have been looking into Node.js, express and Nowjs and love how easy it is to have real time interactions between clients. My background is mostly from CodeIgniter MVC using PHP and MYSql. I want to re make a current web project of mine from scratch to make everything better and more real time with this newer technology. After researching and doing test examples I want to use node.js , express and Nowjs for the real time interactions once someone connects to the socket.io to pull data back to clients. But use Code Igniter for the control of the site and user management , possible shopping cart/store , pretty much everything else. This is purely due to time constraints and that I am already familiar with doing it that way. I have been looking at MongoDB as an alternative to MySql, Basically the app is going to be multiple chat rooms all on one page. with the ability of notifications and private messaging. Lots of data transfer and images. before I started piecing it together I wanted to get people who have already done something similar. My model would use Code Igniter and MySQL to render the page and then connect them onto a node.js server and broadcast using express and nowjs would using a mongoDB be better than mySQL for tons of messages and data being stored or MYSQL? Also does it make since to not make the whole site on Node.js , kinda piece it together like that?

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  • MySQL Table Loop using PHP

    - by JM4
    I have an online form which collects consumer data and stores in a dedicated MySQL database. In some instances, data is passed in the URL under the "RefID" variable which is also stored in the database and attached to each registration. I use the 'mysql_num_rows ($result)' to fetch all agent details on another page but this only returns ALL available details. My goal is as follows: GOAL I want to create an HTML table in which rows are automatically generated based on the list of all registrations on my site. A new row is created IF and ONLY IF a unique RefID is present on that particular record. In the event the field is NULL, it is reported on a single line. In short, the HTML table could look something like this: RefID - Number of Enrollments abc123 - 10 baseball - 11 twonk - 7 NULL - 33 Where abc123 is a particular RefID and 10 is the number of times that RefID appears in the DB. If a new registration comes in with RefID = "horses", a new row is created, showing "horses - 1". The HTML table will be viewable by account administrators needing to see the number of enrollments for a particular RefID (which they won't know ahead of time). Anybody have any suggestions?

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  • How should I solve this MySql problem (PHP) ? (Beginner)

    - by Camran
    I have several tables in a MySql database. I have a classifieds website, and at the bottom I display the users last visited classifieds. I do this by storing the ID:s of the ads to an array in the cookie. Now, my db is made up like this kindof: Main Table: // Stores global information, ie these fields have to be filled out in every record, never be blank ID Price category Seller Item Table: // Stores descriptive info about whats for sale ID AD_ID (FK) //This is the same as ID in the MAIN TABLE Color Size Mileage etc My problem is that I need to know what category the ad is in, in order to query mysql for the right information I think. So I need two variables, but the cookie only has one (ID) stored. Offcourse I could make two queries, first one just matching the ID to the main_table and fetch the category from the Main_table. Then make the second query and fetch all other info from the right table. Here is an example if the category was Vehicles: SELECT * FROM main_table, vehicles_table, WHERE main_table.id=$id_from_cookie AND main_table.ad_id=vehicles_table.ad_id As you can see above, I need the category to write in what table to check, right? But I think there must be a smarter way, like fetching them in one single query using only one variable (id from cookie)? How should I do this? Understand? Let me know if you need more input... Thanks

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  • How do I remove 3 characters from the end of an NSURL?

    - by saywhatman
    Hey, my first question! I've been able to code up most of this RSS reader without enlisting help (through a lot of searches through stackoverflow!) but I'm stumped here. NSString *urlbase = [[NSString alloc] initWithFormat:[links3 objectAtIndex:indexPath.row]]; [[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlbase]]; NSCharacterSet *whitespaces = [NSCharacterSet whitespaceCharacterSet]; NSPredicate *noEmptyStrings = [NSPredicate predicateWithFormat:@"SELF != ''"]; NSArray *parts = [urlbase componentsSeparatedByCharactersInSet:whitespaces]; NSArray *filteredArray = [parts filteredArrayUsingPredicate:noEmptyStrings]; urlbase = [filteredArray componentsJoinedByString:@" "]; NSLog(@"%@ %i" , urlbase, 4353); [[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlbase]]; The links3 array is a NSMutableArray with strings. The first few lines work flawlessly in eliminating the space at the beginning each string from that array, which is stored in 'urlbase' so they look fine when they come out. When we NSLog urlbase, we see: http://www.feedzilla.com/r/D7E6204FEDBFE541314B997AAB5D2DF9CBA2EFEE But, when we use: [[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlbase]] We see: http://www.feedzilla.com/r/D7E6204FEDBFE541314B997AAB5D2DF9CBA2EFEE%0A How can I fix this? Can I remove those tail elements somehow? Thanks!

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  • Is this the best way to grab common elements from a Hash of arrays?

    - by Hulihan Applications
    I'm trying to get a common element from a group of arrays in Ruby. Normally, you can use the & operator to compare two arrays, which returns elements that are present or common in both arrays. This is all good, except when you're trying to get common elements from more than two arrays. However, I want to get common elements from an unknown, dynamic number of arrays, which are stored in a hash. I had to resort to using the eval() method in ruby, which executes a string as actual code. Here's the function I wrote: def get_common_elements_for_hash_of_arrays(hash) # get an array of common elements contained in a hash of arrays, for every array in the hash. # ["1","2","3"] & ["2","4","5"] & ["2","5","6"] # => ["2"] # eval("[\"1\",\"2\",\"3\"] & [\"2\",\"4\",\"5\"] & [\"2\",\"5\",\"6\"]") # => ["2"] eval_string_array = Array.new # an array to store strings of Arrays, ie: "[\"2\",\"5\",\"6\"]", which we will join with & to get all common elements hash.each do |key, array| eval_string_array << array.inspect end eval_string = eval_string_array.join(" & ") # create eval string delimited with a & so we can get common values return eval(eval_string) end example_hash = {:item_0 => ["1","2","3"], :item_1 => ["2","4","5"], :item_2 => ["2","5","6"] } puts get_common_elements_for_hash_of_arrays(example_hash) # => 2 This works and is great, but I'm wondering...eval, really? Is this the best way to do it? Are there even any other ways to accomplish this(besides a recursive function, of course). If anyone has any suggestions, I'm all ears. Otherwise, Feel free to use this code if you need to grab a common item or element from a group or hash of arrays, this code can also easily be adapted to search an array of arrays.

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  • Another C++ question, delete not working?

    - by kyeana
    New to c++, and am having a problem with delete and destructor (I am sure i am making a stupid mistake here, but haven't been able to figure it out as of yet). When i step through into the destructor, and attepmt to call delete on a pointer, the message shows up "Cannot access memory at address some address." The relevant code is: /* * Removes the front item of the linked list and returns the value stored * in that node. * * TODO - Throws an exception if the list is empty */ std::string LinkedList::RemoveFront() { LinkedListNode *n = pHead->GetNext(); // the node we are removing std::string rtnData = n->GetData(); // the data to return // un-hook the node from the linked list pHead->SetNext(n->GetNext()); n->GetNext()->SetPrev(pHead); // delete the node delete n; n=0; size--; return rtnData; } and /* * Destructor for a linked node. * * Deletes all the dynamically allocated memory, and sets those pointers to 0. */ LinkedListNode::~LinkedListNode() { delete pNext; // This is where the error pops up delete pPrev; pNext=0; pPrev=0; }

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  • Proper way to reassign pointers in c++

    - by user272689
    I want to make sure i have these basic ideas correct before moving on (I am coming from a Java/Python background). I have been searching the net, but haven't found a concrete answer to this question yet. When you reassign a pointer to a new object, do you have to call delete on the old object first to avoid a memory leak? My intuition is telling me yes, but i want a concrete answer before moving on. For example, let say you had a class that stored a pointer to a string class MyClass { private: std::string *str; public: MyClass (const std::string &_str) { str=new std::string(_str); } void ChangeString(const std::string &_str) { // I am wondering if this is correct? delete str; str = new std::string(_str) /* * or could you simply do it like: * str = _str; */ } .... In the ChangeString method, which would be correct? I think i am getting hung up on if you dont use the new keyword for the second way, it will still compile and run like you expected. Does this just overwrite the data that this pointer points to? Or does it do something else? Any advice would be greatly appricated :D

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  • Is this the best way to grab Common element from a Hash of arrays?

    - by Hulihan Applications
    I'm trying to get a common element from a group of arrays in Ruby. Normally, you can use the & operator to compare two arrays, which returns elements that are present or common in both arrays. This is all good, except when you're trying to get common elements from more than two arrays. However, I want to get common elements from an unknown, dynamic number of arrays, which are stored in a hash. I had to resort to using the eval() method in ruby, which executes a string as actual code. Here's the function I wrote: def get_common_elements_for_hash_of_arrays(hash) # get an array of common elements contained in a hash of arrays, for every array in the hash. # ["1","2","3"] & ["2","4","5"] & ["2","5","6"] # => ["2"] # eval("[\"1\",\"2\",\"3\"] & [\"2\",\"4\",\"5\"] & [\"2\",\"5\",\"6\"]") # => ["2"] eval_string_array = Array.new # an array to store strings of Arrays, ie: "[\"2\",\"5\",\"6\"]", which we will join with & to get all common elements hash.each do |key, array| eval_string_array << array.inspect end eval_string = eval_string_array.join(" & ") # create eval string delimited with a & so we can get common values return eval(eval_string) end example_hash = {:item_0 => ["1","2","3"], :item_1 => ["2","4","5"], :item_2 => ["2","5","6"] } puts get_common_elements_for_hash_of_arrays(example_hash) # => 2 This works and is great, but I'm wondering...eval, really? Is this the best way to do it? Are there even any other ways to accomplish this(besides a recursive function, of course). If anyone has any suggestions, I'm all ears. Otherwise, Feel free to use this code if you need to grab a common item or element from a group or hash of arrays, this code can also easily be adapted to search an array of arrays.

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