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• How do I efficiently parse a CSV file in Perl?

  - by Mike

  I'm working on a project that involves parsing a large csv formatted file in Perl and am looking to make things more efficient. My approach has been to split() the file by lines first, and then split() each line again by commas to get the fields. But this suboptimal since at least two passes on the data are required. (once to split by lines, then once again for each line). This is a very large file, so cutting processing in half would be a significant improvement to the entire application. My question is, what is the most time efficient means of parsing a large CSV file using only built in tools? note: Each line has a varying number of tokens, so we can't just ignore lines and split by commas only. Also we can assume fields will contain only alphanumeric ascii data (no special characters or other tricks). Also, i don't want to get into parallel processing, although it might work effectively. edit It can only involve built-in tools that ship with Perl 5.8. For bureaucratic reasons, I cannot use any third party modules (even if hosted on cpan) another edit Let's assume that our solution is only allowed to deal with the file data once it is entirely loaded into memory. yet another edit I just grasped how stupid this question is. Sorry for wasting your time. Voting to close.

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• Outlook VSTO AddIn for Meetings

  - by BigDubb

  We have created a VSTO addin for Outlook Meetings. As part of this we trap on the SendEvent of the message on the FormRegionShowing event: _apptEvents.Send += new Microsoft.Office.Interop.Outlook.ItemEvents_SendEventHandler(_apptEvents_Send); The method _apptEvents_Send then tests on a couple of properties and exits where appropriate. private void _apptEvents_Send(ref bool Cancel) { if (!_Qualified) { MessageBox.Show("Meeting has not been qualified", "Not Qualified Meeting", MessageBoxButtons.OK, MessageBoxIcon.Information); chkQualified.Focus(); Cancel = true; } } The problem that we're having is that some users' messages get sent twice. Once when the meeting is sent and a second time when the user re-opens outlook. I've looked for memory leaks, thinking that something might not be getting disposed of properly, and have added explicit object disposal on all finally calls to try and make sure resources are managed, but still getting the functionality incosistently across the organization. i.e. I never encountered the problem during development, nor other developers during testing. All users are up to date on framework (3.5 SP1) and Hotfixes for Outlook. Does anyone have any ideas on what might be causing this? Any ideas anyone might have would be greatly appreciated.

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• Question on passing a pointer to a structure in C to a function?

  - by worlds-apart89

  Below, I wrote a primitive singly linked list in C. Function "addEditNode" MUST receive a pointer by value, which, I am guessing, means we can edit the data of the pointer but can not point it to something else. If I allocate memory using malloc in "addEditNode", when the function returns, can I see the contents of first-next ? Second question is do I have to free first-next or is it only first that I should free? I am running into segmentation faults on Linux. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { int value; list_node_t *next; }; void addEditNode(list_node_t *node) { node->value = 10; node->next = (list_node_t*) malloc(sizeof(list_node_t)); node->next->value = 1; node->next->next = NULL; } int main() { list_node_t *first = (list_node_t*) malloc(sizeof(list_node_t)); first->value = 1; first->next = NULL; addEditNode(first); free(first); return 0; }

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• Why use shorter VARCHAR(n) fields?

  - by chryss

  It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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• How can I use io.StringIO() with the csv module?

  - by Tim Pietzcker

  I tried to backport a Python 3 program to 2.7, and I'm stuck with a strange problem: >>> import io >>> import csv >>> output = io.StringIO() >>> output.write("Hello!") # Fail: io.StringIO expects Unicode Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' >>> output.write(u"Hello!") # This works as expected. 6L >>> writer = csv.writer(output) # Now let's try this with the csv module: >>> csvdata = [u"Hello", u"Goodbye"] # Look ma, all Unicode! (?) >>> writer.writerow(csvdata) # Sadly, no. Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' According to the docs, io.StringIO() returns an in-memory stream for Unicode text. It works correctly when I try and feed it a Unicode string manually. Why does it fail in conjunction with the csv module, even if all the strings being written are Unicode strings? Where does the str come from that causes the Exception? (I do know that I can use StringIO.StringIO() instead, but I'm wondering what's wrong with io.StringIO() in this scenario)

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• Reading and writing to files simultaneously?

  - by vipersnake005

  Moved the question here. Suppose, I want to store 1,000,000,000 integers and cannot use my memory. I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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• Drawing line graphics leads Flash to spiral out of control!

  - by drpepper

  Hi, I'm having problems with some AS3 code that simply draws on a Sprite's Graphics object. The drawing happens as part of a larger procedure called on every ENTER_FRAME event of the stage. Flash neither crashes nor returns an error. Instead, it starts running at 100% CPU and grabs all the memory that it can, until I kill the process manually or my computer buckles under the pressure when it gets up to around 2-3 GB. This will happen at a random time, and without any noticiple slowdown beforehand. WTF? Has anyone seen anything like this? PS: I used to do the drawing within a MOUSE_MOVE event handler, which brought this problem on even faster. PPS: I'm developing on Linux, but reproduced the same problem on Windows. UPDATE: You asked for some code, so here we are. The drawing function looks like this: public static function drawDashedLine(i_graphics : Graphics, i_from : Point, i_to : Point, i_on : Number, i_off : Number) : void { const vecLength : Number = Point.distance(i_from, i_to); i_graphics.moveTo(i_from.x, i_from.y); var dist : Number = 0; var lineIsOn : Boolean = true; while(dist < vecLength) { dist = Math.min(vecLength, dist + (lineIsOn ? i_on : i_off)); const p : Point = Point.interpolate(i_from, i_to, 1 - dist / vecLength); if(lineIsOn) i_graphics.lineTo(p.x, p.y); else i_graphics.moveTo(p.x, p.y); lineIsOn = !lineIsOn; } } and is called like this (m_graphicsLayer is a Sprite): m_graphicsLayer.graphics.clear(); if (m_destinationPoint) { m_graphicsLayer.graphics.lineStyle(2, m_fixedAim ? 0xff0000 : 0x333333, 1); drawDashedLine(m_graphicsLayer.graphics, m_initialPos, m_destinationPoint, 10, 10); }

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• Need help getting parent reference to child view controller

  - by Andy

  I've got the following code in one of my view controllers: - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { switch (indexPath.section) { case 0: // "days" section tapped { DayPicker *dayPicker = [[DayPicker alloc] initWithStyle:UITableViewStylePlain]; dayPicker.rowLabel = self.activeDaysLabel; dayPicker.selectedDays = self.newRule.activeDays; [self.navigationController pushViewController:dayPicker animated:YES]; [dayPicker release]; break; ... Then, in the DayPicker controller, I do some stuff to the dayPicker.rowLabel property. Now, when the dayPicker is dismissed, I want the value in dayPicker.rowLabel to be used as the cell.textLabel.text property in the cell that called the controller in the first place (i.e., the cell label becomes the option that was selected within the DayPicker controller). I thought that by using the assignment operator to set dayPicker.rowLabel = self.activeDaysLabel, the two pointed to the same object in memory, and that upon dismissing the DayPicker, my first view controller, which uses self.activeDaysLabel as the cell.textLabel.text property for the cell in question, would automagically pick up the new value of the object. But no such luck. Have I missed something basic here, or am I going about this the wrong way? I originally passed a reference to the calling view controller to the child view controller, but several here told me that was likely to cause problems, being a circular reference. That setup worked, though; now I'm not sure how to accomplish the same thing "the right way." As usual, thanks in advance for your help.

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• How to optimalize my game calendar in C#?

  - by MartyIX

  Hi, I've implemented a simple calendar (message system) for my game which consists from: 1) List<Event> calendar; 2) public class Event { /// <summary> /// When to process the event /// </summary> public Int64 when; /// <summary> /// Which object should process the event /// </summary> public GameObject who; /// <summary> /// Type of event /// </summary> public EventType what; public int posX; public int posY; public int EventID; } 3) calendar.Add(new Event(...)) The problem with this code is that even thought the number of messages is not excessise per second. It allocates still new memory and GC will once need to take care of that. The garbage collection may lead to a slight lag in my game and therefore I'd like to optimalize my code. My considerations: To change Event class in a structure - but the structure is not entirely small and it takes some time to copy it wherever I need it. Reuse Event object somehow (add queue with used events and when new event is needed I'll just take from this queue). Does anybody has other idea how to solve the problem? Thanks for suggestions!

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• (How) Can I approximate a "dynamic" index (key extractor) for Boost MultiIndex?

  - by Sarah

  I have a MultiIndex container of boost::shared_ptrs to members of class Host. These members contain private arrays bool infections[NUM_SEROTYPES] revealing Hosts' infection statuses with respect to each of 1,...,NUM_SEROTYPES serotypes. I want to be able to determine at any time in the simulation the number of people infected with a given serotype, but I'm not sure how: Ideally, Boost MultiIndex would allow me to sort, for example, by Host::isInfected( int s ), where s is the serotype of interest. From what I understand, MultiIndex key extractors aren't allowed to take arguments. An alternative would be to define an index for each serotype, but I don't see how to write the MultiIndex container typedef ... in such an extensible way. I will be changing the number of serotypes between simulations. (Do experienced programmers think this should be possible? I'll attempt it if so.) There are 2^(NUM_SEROTYPES) possible infection statuses. For small numbers of serotypes, I could use a single index based on this number (or a binary string) and come up with some mapping from this key to actual infection status. Counting is still darn slow. I could maintain a separate structure counting the total numbers of infecteds with each serotype. The synchrony is a bit of a pain, but the memory is fine. I would prefer a slicker option, since I would like to do further sorts on other host attributes (e.g., after counting the number infected with serotype s, count the number of those infected who are also in a particular household and have a particular age). Thanks in advance.

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• Any workarounds for non-static member array initialization?

  - by TomiJ

  In C++, it's not possible to initialize array members in the initialization list, thus member objects should have default constructors and they should be properly initialized in the constructor. Is there any (reasonable) workaround for this apart from not using arrays? [Anything that can be initialized using only the initialization list is in our application far preferable to using the constructor, as that data can be allocated and initialized by the compiler and linker, and every CPU clock cycle counts, even before main. However, it is not always possible to have a default constructor for every class, and besides, reinitializing the data again in the constructor rather defeats the purpose anyway.] E.g. I'd like to have something like this (but this one doesn't work): class OtherClass { private: int data; public: OtherClass(int i) : data(i) {}; // No default constructor! }; class Foo { private: OtherClass inst[3]; // Array size fixed and known ahead of time. public: Foo(...) : inst[0](0), inst[1](1), inst[2](2) {}; }; The only workaround I'm aware of is the non-array one: class Foo { private: OtherClass inst0; OtherClass inst1; OtherClass inst2; OtherClass *inst[3]; public: Foo(...) : inst0(0), inst1(1), inst2(2) { inst[0]=&inst0; inst[1]=&inst1; inst[2]=&inst2; }; }; Edit: It should be stressed that OtherClass has no default constructor, and that it is very desirable to have the linker be able to allocate any memory needed (one or more static instances of Foo will be created), using the heap is essentially verboten. I've updated the examples above to highlight the first point.

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• Python 2.6 does not like appending to existing archives in zip files

  - by user313661

  Hello, In some Python unit tests of a program I'm working on we use in-memory zipfiles for end to end tests. In SetUp() we create a simple zip file, but in some tests we want to overwrite some archives. For this we do "zip.writestr(archive_name, zip.read(archive_name) + new_content)". Something like import zipfile from StringIO import StringIO def Foo(): zfile = StringIO() zip = zipfile.ZipFile(zfile, 'a') zip.writestr( "foo", "foo content") zip.writestr( "bar", "bar content") zip.writestr( "foo", zip.read("foo") + "some more foo content") print zip.read("bar") Foo() The problem is that this works fine in Python 2.4 and 2.5, but not 2.6. In Python 2.6 this fails on the print line with "BadZipfile: File name in directory "bar" and header "foo" differ." It seems that it is reading the correct file bar, but that it thinks it should be reading foo instead. I'm at a loss. What am I doing wrong? Is this not supported? I tried searching the web but could find no mention of similar problems. I read the zipfile documentation, but could not find anything (that I thought was) relevant, especially since I'm calling read() with the filename string. Any ideas? Thank you in advance!

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• Objective C iPhone performance issue

  - by Asad Khan

  Ok guys I am developing an iPhone app I have a Model class which follows a Singleton design pattern. Now I have an NSArray in it which is initialized to around some 1000 NSStrings in the init method. Now I need to use this data in some view controller. so I import Model.h, I create an array of NSString objects in view controller & set the data to it. But now the problem is that now I have 2000 NSStrings currently allocated, which I believe is not a good thing on iPhone due to memory considerations. releasing model object wont help because I've overrided release method to release nothing according to the pattern & I cannot change the design now because now a lot of code works on the assumption of model being a singleton. & in future maybe the initial NSStrings may grow to 2000 or even more & then I'll have 4000 NSStrings allocated at one time .... I am a little confused on how to go about it any suggestions

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• GTK+: How do I process RadioMenuItem choice without marking it chosen? And vise versa

  - by eugene.shatsky

  In my program, I've got a menu with a group of RadioMenuItem entries. Choosing one of them should trigger a function which can either succeed or fail. If it fails, this RadioMenuItem shouldn't be marked chosen (the previous one should persist). Besides, sometimes I want to set marked item without running the choice processing function. Here is my current code: # Update seat menu list def update_seat_menu(self, seats, selected_seat=None): seat_menu = self.builder.get_object('seat_menu') # Delete seat menu items for menu_item in seat_menu: # TODO: is it a good way? does remove() delete obsolete menu_item from memory? if menu_item.__class__.__name__ == 'RadioMenuItem': seat_menu.remove(menu_item) # Fill menu with new items group = [] for seat in seats: menu_item = Gtk.RadioMenuItem.new_with_label(group, str(seat[0])) group = menu_item.get_group() seat_menu.append(menu_item) if str(seat[0]) == selected_seat: menu_item.activate() menu_item.connect("activate", self.choose_seat, str(seat[0])) menu_item.show() # Process item choice def choose_seat(self, entry, seat_name): # Looks like this is called when item is deselected, too; must check if active if entry.get_active(): # This can either succeed or fail self.logind.AttachDevice(seat_name, '/sys'+self.device_syspath, True) Chosen RadioMenuItem gets marked irrespective of the choose_seat() execution result; and the only way to set marked item without triggering choose_seat() is to re-run update_seat_menu() with selected_seat argument, which is an overkill. I tried to connect choose_seat() with 'button-release-event' instead of 'activate' and call entry.activate() in choose_seat() if AttachDevice() succeeds, but this resulted in whole X desktop lockup until AttachDevice() timed out, and chosen item still got marked.

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• Still some questions about USB

  - by b-gen-jack-o-neill

  Hi, few days ago I asked here about implementing USB. Now, If I may, would like to ask few more questions, about thing I dind´t quite understood. So, first, If I am right, Windows has device driver for USB interface, for the physical device that sends and receives communication. But what this driver offers to system (user)? I mean, USB protocol is made so its devices are adressed. So you first adress device than send message to it. But how sophisticted is the device controller (HW) and its driver? Is it so sophisticated that it is a chip you just send device adress and data, and it writes the outcomming data out and incomming data to some internal register to be read, or thru DMA directly to memory? Or, how its drivers (SW) really work? Does its driver has some advanced functions like send _data to _device? Becouse I somewhat internally hope there is a way to directly send some data thru USB, maybe by calling USB drivers itself? Is there any good article, tutorial you know about to really explain how all this logic works? Thanks.

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• Need help in Hashtable implementation

  - by rafael

  Hi all, i'm quite a beginner in C# , i tried to write a program that extract words from an entered string, the user has to enter a minimum length for the word to filter the words output ... my code doesn't look good or intuitive, i used two arrays countStr to store words , countArr to store word length corresponding to each word .. but the problem is i need to use hashtables instead of those two arrays , because both of their sizes are depending on the string length that the user enter , i think that's not too safe for the memory or something ? here's my humble code , again i'm trying to replace those two arrays with one hashtable , how can this be done ? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Collections; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { int i = 0 ; int j = 0; string myString = ""; int counter = 0; int detCounter = 0; myString = Console.ReadLine(); string[] countStr = new string[myString.Length]; int[] countArr = new int[myString.Length]; Console.Write("Enter minimum word length:"); detCounter = int.Parse(Console.ReadLine()); for (i = 0; i < myString.Length; i++) { if (myString[i] != ' ') { counter++; countStr[j] += myString[i]; } else { countArr[j] = counter; counter = 0; j++; } } if (i == myString.Length) { countArr[j] = counter; } for (i = 0; i < myString.Length ; i++) { if (detCounter <= countArr[i]) { Console.WriteLine(countStr[i]); } } Console.ReadLine(); } } }

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• What are provenly scalable data persistence solutions for consumer profiles?

  - by Hubbard

  Consumer profiles with analytical scores [ConsumerID, 1..n demographical variables, 1...n analytical scores e.g. "likely to churn" "likely to buy an item 100$ in worth" etc.] have to be possible to query fast if they are to be used in customizing web-sites, consumer communications etc. Well. If you have: Large number of consumers Large profiles with a huge set of variables (as profiles describing human behaviour are likely to be..) ...you are in trouble. If you really have a physical relational database to which you target a query and then a physical disk starts to rotate someplace to give you an individual profile or a set of profiles, the profile user (a web site customizing a page, a recommendation engine making a recommendation..) has died of boredom before getting any observable results. There is the possibility of having the profiles in memory, which would of course increase the performance hugely. What are the most proven solutions for a fast-response, scalable consumer profile storage? Is there a shootout of these someplace?

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• std::map keys in C++

  - by Soumava

  I have a requirement to create two different maps in C++. The Key is of type CHAR * and the Value is a pointer to a struct. I am filling 2 maps with these pairs, in separate iterations. After creating both maps I need find all such instances in which the value of the string referenced by the CHAR * are same. For this i am using the following code : typedef struct _STRUCTTYPE { .. } STRUCTTYPE, *PSTRUCTTYPE; typedef pair {CHAR *,PSTRUCTTYPE} kvpair; .. CHAR *xyz; PSTRUCTTYPE abc; after filling the information; Map.insert (kvpair(xyz,abc)); the above is repeated x times for the first map, and y times for the second map. after both are filled out; std::map {CHAR *, PSTRUCTTYPE} :: iterator Iter,findIter; for (Iter=iteratedMap-begin();Iter!=iteratedMap-end();mapIterator++) { char *key = Iter-first; printf("%s\n",key); findIter=otherMap-find(key); //printf("%u",findIter-second); if (findIter!=otherMap-end()) { printf("Match!\n"); } } The above code does not show any match, although the list of keys in both maps show obvious matches. My understanding is that the equals operator for CHAR * just equates the memory address of the pointers. My question is, what should i do to alter the equals operator for this type of key or could I use a different datatype for the string? *note : {} has been used instead of angle brackets as the content inside angle brackets was not showing up in the post.

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• Using an objects date (without time) for a table header instead of an objects date and time (iphone)

  - by billywilliamton

  I've been working on an iphone project and have run into an issue. Currently In the table view where it displays all the objects, I use headers based on the objects datePerformed field. The only problem is that my code apparently creates a header that contains both the date and time resulting in objects not being grouped solely by their date as I intended, but rather based on their date and time. I'm not sure if it matters, but when an object is created I use a date picker to pick the date, but not the time. I was wondering if anyone could give me any suggestions or advice. Here is the code where i set up the fetchedResultsController - (NSFetchedResultsController *)fetchedResultsController { if (fetchedResultsController != nil) { return fetchedResultsController; } // Create and configure a fetch request with the Exercise entity. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Exercise" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // Create the sort descriptors array using date and name NSSortDescriptor *dateDescriptor = [[NSSortDescriptor alloc] initWithKey:@"datePerformed" ascending:NO]; NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:dateDescriptor, nameDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; // Create and initialize the fetch results controller NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"datePerformed" cacheName:@"Root"]; self.fetchedResultsController = aFetchedResultsController; fetchedResultsController.delegate = self; // Memory management calls [aFetchedResultsController release]; [fetchRequest release]; [dateDescriptor release]; [nameDescriptor release]; [sortDescriptors release]; return fetchedResultsController; } Here's where I set up the table header properties - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section { // Display the exercise' date as section headings. return [[[fetchedResultsController sections] objectAtIndex:section] name]; } Any suggestions welcome. Thanks for your time. -Billy Williamton

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• how to change uibutton title at runtime in objective c?

  - by Sarah

  Hello, I know this question is asked many a times,and i am also implementing the same funda for chanding the title of the uibutton i guess. Let me clarify my problem first. I have one uibutton named btnType, on clicking of what one picker pops up and after selecting one value,i am hitting done button to hide the picker and at the same time i am changing the the title of the uibutton with code [btnType setTitle:btnTitle forState:UIControlEventTouchUpInside]; [btnType setTitleColor:[UIColor redColor] forState:UIControlEventAllEvents]; But with my surpriaze,it is not changed and application crashes with signal EXC_BAD_ACCESS. I am not getting where i am making mistake.I have allocated memory to the btnType at viewdidLoad. Also I am using -(IBAction)pressAddType { toolBar.hidden = FALSE; dateTypePicker.hidden = FALSE; } event on pressing the button to open the picker. Also i would like to mention that i have made connection with IB with event TouchUpInside for pressAddType. Any guesses? I will be grateful if you could help me. Thanks.

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• C++ ulong to class method pointer and back

  - by Simone Margaritelli

  Hi guys, I'm using a hash table (source code by Google Inc) to store some method pointers defined as: typedef Object *(Executor::*expression_delegate_t)( vframe_t *, Node * ); Where obviously "Executor" is the class. The function prototype to insert some value to the hash table is: hash_item_t *ht_insert( hash_table_t *ht, ulong key, ulong data ); So basically i'm doing the insert double casting the method pointer: ht_insert( table, ASSIGN, reinterpret_cast<ulong>( (void *)&Executor::onAssign ) ); Where table is defined as a 'hash_table_t *' inside the declaration of the Executor class, ASSIGN is an unsigned long value, and 'onAssign' is the method I have to map. Now, Executor::onAssign is stored as an unsigned long value, its address in memory I think, and I need to cast back the ulong to a method pointer. But this code: hash_item_t* item = ht_find( table, ASSIGN ); expression_delegate_t delegate = reinterpret_cast < expression_delegate_t > (item->data); Gives me the following compilation error : src/executor.cpp:45: error: invalid cast from type ‘ulong’ to type ‘Object* (Executor::*)(vframe_t*, Node*)’ I'm using GCC v4.4.3 on a x86 GNU/Linux machine. Any hints?

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• Very fast document similarity

  - by peyton

  Hello, I am trying to determine document similarity between a single document and each of a large number of documents (n ~= 1 million) as quickly as possible. More specifically, the documents I'm comparing are e-mails; they are grouped (i.e., there are folders or tags) and I'd like to determine which group is most appropriate for a new e-mail. Fast performance is critical. My a priori assumption is that the cosine similarity between term vectors is appropriate for this application; please comment on whether this is a good measure to use or not! I have already taken into account the following possibilities for speeding up performance: Pre-normalize all the term vectors Calculate a term vector for each group (n ~= 10,000) rather than each e-mail (n ~= 1,000,000); this would probably be acceptable for my application, but if you can think of a reason not to do it, let me know! I have a few questions: If a new e-mail has a new term never before seen in any of the previous e-mails, does that mean I need to re-compute all of my term vectors? This seems expensive. Is there some clever way to only consider vectors which are likely to be close to the query document? Is there some way to be more frugal about the amount of memory I'm using for all these vectors? Thanks!

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• How to construct objects based on XML code?

  - by the_drow

  I have XML files that are representation of a portion of HTML code. Those XML files also have widget declarations. Example XML file: <message id="msg"> <p> <Widget name="foo" type="SomeComplexWidget" attribute="value"> inner text here, sets another attribute or inserts another widget to the tree if needed... </Widget> </p> </message> I have a main Widget class that all of my widgets inherit from. The question is how would I create it? Here are my options: Create a compile time tool that will parse the XML file and create the necessary code to bind the widgets to the needed objects. Advantages: No extra run-time overhead induced to the system. It's easy to bind setters. Disadvantages: Adds another step to the build chain. Hard to maintain as every widget in the system should be added to the parser. Use of macros to bind the widgets. Complex code Find a method to register all widgets into a factory automatically. Advantages: All of the binding is done completely automatically. Easier to maintain then option 1 as every new widget will only need to call a WidgetFactory method that registers it. Disadvantages: No idea how to bind setters without introducing a maintainability nightmare. Adds memory and run-time overhead. Complex code What do you think is better? Can you guys suggest a better solution?

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• JavaCard monitoring folder

  - by GxG

  I want to write a two way application: applet for javacard and an application in C#. I've got the C# covered but i want to know if with JavaCard i can monitor a folder on the memory and how would i go about doing that. I have a shared folder let's call it temp in which i want to store buffer information between the simulated smartcard and the C# application. The C# application will only read from that folder and display the information, but also it will write requests towards the smartcard. For example i simulate entering the PIN for the card. The applet will write a file containing available options and the C# application will read that file and display those options; from the C# app i will chose and option and write a request file in the same folder. This is when the smartcard which is monitoring that folder will read the request and issue a response. Can i make the smartcard monitor that folder? I was thinking of using encrypted XML files for the request/response operations. But simple .txt files are good to. I am limited to using JavaCard v2.2.1, and every operation has to be encrypted/decrypted. (with the ciphering i have no problem)

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• What does the destructor do silently?

  - by zhanwu

  Considering the following code which looks like that the destructor doesn't do any real job, valgrind showed me clearly that it has memory leak without using the destructor. Any body can explain me what does the destructor do in this case? #include <iostream> using namespace std; class A { private: int value; A* follower; public: A(int); ~A(); void insert(int); }; A::A(int n) { value = n; follower = NULL; } A::~A() { if (follower != NULL) delete follower; cout << "do nothing!" << endl; } void A::insert(int n) { if (this->follower == NULL) { A* f = new A(n); this->follower = f; } else this->follower->insert(n); } int main(int argc, char* argv[]) { A* objectA = new A(1); int i; for (i = 0; i < 10; i++) objectA->insert(i); delete objectA; }

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