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  • boost::unordered_map is... ordered?

    - by Thanatos
    I have a boost::unordered_map, but it appears to be in order, giving me an overwhelming feeling of "You're Doing It Wrong". Why is the output to this in order? I would've expected the underlying hashing algorithm to have randomized this order: #include <iostream> #include <boost/unordered_map.hpp> int main() { boost::unordered_map<int, int> im; for(int i = 0; i < 50; ++i) { im.insert(std::make_pair(i, i)); } boost::unordered_map<int, int>::const_iterator i; for(i = im.begin(); i != im.end(); ++i) { std::cout << i->first << ", " << i->second << std::endl; } return 0; } ...gives me... 0, 0 1, 1 2, 2 ... 47, 47 48, 48 49, 49

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  • C++ iterator and const_iterator problem for own container class

    - by BaCh
    Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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  • Java Variable Initialization

    - by Samuel Brainard
    Here's a piece of code I wrote. public class cube { private int length; private int breadth; private int height; private int volume; private int density; private int weight; public cube(int l,int b,int h, int d) { length=l; breadth=b; height=h; density=d; } public void volmeShow(){ volume=length*breadth*height; System.out.println("The Volume of the cube is "+this.volume); So if I implement the above cube class like this, public class cubeApp { public static void main(String[] args){ cube mycube = new cube(5,6,9,2); mycube.volumeShow(); I get an output that tells me Volume is 270. But I get an output that says Volume is 0 if I define the volume variable like this: public class cube { private int length; private int breadth; private int height; private int volume=length*breadth*height; private int density; private int weight; public cube(int l,int b,int h, int d) { length=l; breadth=b; height=h; density=d; } public void volmeShow(){ System.out.println("The Volume of the cube is "+this.volume); Can somebody please explain why this is happening? Thanks, Samuel.

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  • jquery : ul, li parent multiple child sub-child toggling

    - by user360826
    hello, my main question is as follows: how to show only the first subchild of a ul or li upon clicking the enclosing parent. eg: <ul> Grandparent <li> Child1 <li> Grandchild11</li></li> <li> Child2 <li>GrandChild21</li><li>grandchild22</li></li> </ul> so, for example I would like something to the effect of <script> $('ul').click(function(){ $('ul').children('first li').toggle() }); $('li').click(function(){ $('li').children('first li').toggle() }); </script> meaning: when i click ul, i only see the first child node (child1 and child2 will be shown, but not the grandchildren). when i click child1 or child2 i see the respective grandchild. grandchild is not shown upon clicking grandparent, only upon clicking child1 or child2. i know i am reinventing the wheel of some pre-coded solution, but any help would be largely appreciated!

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  • trouble with state monad composition

    - by user1308560
    I was trying out the example given at http://www.haskell.org/haskellwiki/State_Monad#Complete_and_Concrete_Example_1 How this makes the solution composible is beyond my understanding. Here is what I tried but I get compile errors as follows: Couldn't match expected type `GameValue -> StateT GameState Data.Functor.Identity.Identity b0' with actual type `State GameState GameValue' In the second argument of `(>>=)', namely `g2' In the expression: g1 >>= g2 In an equation for `g3': g3 = g1 >>= g2 Failed, modules loaded: none. Here is the code: See the end lines module StateGame where import Control.Monad.State type GameValue = Int type GameState = (Bool, Int) -- suppose I want to play one game after the other g1 = playGame "abcaaacbbcabbab" g2 = playGame "abcaaacbbcabb" g3 = g1 >>= g2 m2 = print $ evalState g3 startState playGame :: String -> State GameState GameValue playGame [] = do (_, score) <- get return score playGame (x:xs) = do (on, score) <- get case x of 'a' | on -> put (on, score + 1) 'b' | on -> put (on, score - 1) 'c' -> put (not on, score) _ -> put (on, score) playGame xs startState = (False, 0) main str = print $ evalState (playGame str) startState

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  • Making an efficient algorithm

    - by James P.
    Here's my recent submission for the FB programming contest (qualifying round only requires to upload program output so source code doesn't matter). The objective is to find two squares that add up to a given value. I've left it as it is as an example. It does the job but is too slow for my liking. Here's the points that are obviously eating up time: List of squares is being recalculated for each call of getNumOfDoubleSquares(). This could be precalculated or extended when needed. Both squares are being checked for when it is only necessary to check for one (complements). There might be a more efficient way than a double-nested loop to find pairs. Other suggestions? Besides this particular problem, what do you look for when optimizing an algorithm? public static int getNumOfDoubleSquares( Integer target ){ int num = 0; ArrayList<Integer> squares = new ArrayList<Integer>(); ArrayList<Integer> found = new ArrayList<Integer>(); int squareValue = 0; for( int j=0; squareValue<=target; j++ ){ squares.add(j, squareValue); squareValue = (int)Math.pow(j+1,2); } int squareSum = 0; System.out.println( "Target=" + target ); for( int i = 0; i < squares.size(); i++ ){ int square1 = squares.get(i); for( int j = 0; j < squares.size(); j++ ){ int square2 = squares.get(j); squareSum = square1 + square2; if( squareSum == target && !found.contains( square1 ) && !found.contains( square2 ) ){ found.add(square1); found.add(square2); System.out.println( "Found !" + square1 +"+"+ square2 +"="+ squareSum); num++; } } } return num; }

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  • How to Develop Dynamic Plug-In Based Functionality in C#

    - by Matthew
    Hello: I've been looking around for different methods of providing plug-in support for my application. Ideally, I will be creating a core functionality and based on different customers developing different plug-ins/addons such as importing, exporting data etc... What are the some methods available for making a C# application extensible via a plug-in architecture? Lets make up an example. If we have a program that consists of a main menu ( File, Edit, View, et al. ) along with a TreeView that displays different brands of cars grouped by manufacturer ( Ford, GM, for now). Right clicking on a car displays a context menu with the only option being 'delete car'. How could you develop the application so that plug-ins could be deployed so that you could allow one customer to see a new brand in the TreeView, let's say Honda, and also extent the car context menu so that they may now 'paint a car'? In Eclipse/RCP development this is easily handled by extension points and plug-ins. How does C# handle it? I've been looking into developing my own plug-in architecture and reading up on MEF.

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  • Address book Phone number (+45) prefix causing crash!

    - by CCDEV
    Hi Guys... I am having trouble getting phone numbers from the iPhone Addressbook. There is no problem when the number do not contain a country code prefix like +45, but if it does, my app crashes... Is this a known issue? I haven't been able to find anything about it... Thanks EDIT: I get phonenumber like this: -(void)getContact { ABPeoplePickerNavigationController *pp = [[ABPeoplePickerNavigationController alloc] init]; pp.displayedProperties = [NSArray arrayWithObject:[NSNumber numberWithInt:kABPersonPhoneProperty]]; pp.peoplePickerDelegate = self; [self presentModalViewController:pp animated:YES]; [pp release]; } - (void)peoplePickerNavigationControllerDidCancel:(ABPeoplePickerNavigationController *)peoplePicker { // assigning control back to the main controller [self dismissModalViewControllerAnimated:YES]; } - (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson:(ABRecordRef)person { return YES; } -(BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson:(ABRecordRef)person property:(ABPropertyID)property identifier:(ABMultiValueIdentifier)identifier { ABMultiValueRef phoneProperty = ABRecordCopyValue(person,property); saveString = (NSString *)ABMultiValueCopyValueAtIndex(phoneProperty,identifier); saveString = [saveString stringByReplacingOccurrencesOfString:@" " withString:@""]; nummerTextField.text = saveString; }

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  • Why cant we create Object if constructor is in private section?

    - by Abhi
    Dear all I want to know why cant we create object if the constructor is in private section. I know that if i make a method static i can call that method using <classname> :: <methodname(...)>; But why cant we create object is my doubt... I also know if my method is not static then also i can call function by the following... class A { A(); public: void fun1(); void fun2(); void fun3(); }; int main() { A *obj =(A*)malloc(sizeof(A)); //Here we can't use new A() because constructor is in private //but we can use malloc with it, but it will not call the constructor //and hence it is harmful because object may not be in usable state. obj->fun1(); obj->fun2(); obj->fun3(); } So only doubt is why cant we create object when constructor is in private section? Thanks in advance

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  • Why does my program not react to any arguments?

    - by Electric Coffee
    I have a simple test program in C++ that prints out attributes of a circle #include <iostream> #include <stdlib.h> #include "hidden_functions.h" // contains the Circle class using namespace std; void print_circle_attributes(float r) { Circle* c = new Circle(r); cout << "radius: " << c->get_radius() << endl; cout << "diameter: " << c->get_diameter() << endl; cout << "area: " << c->get_area() << endl; cout << "circumference: " << c->get_circumference() << endl; cout << endl; delete c; } int main(int argc, const char* argv[]) { float input = atof(argv[0]); print_circle_attributes(input); return 0; } when I run my program with the parameter 2.4 it outputs: radius: 0.0 diameter: 0.0 area: 0.0 circumference: 0.0 I've previously tested the program without the parameter, but simply using static values, and it ran just fine; so I know there's nothing wrong with the class I made... So what did I do wrong here? Note: the header is called hidden_functions.h because it served to test out how it would work if I had functions not declared in the header

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  • slow mysql count because of subselect

    - by frgt10
    how to make this select statement more faster? the first left join with the subselect is making it slower... mysql> SELECT COUNT(DISTINCT w1.id) AS AMOUNT FROM tblWerbemittel w1 JOIN tblVorgang v1 ON w1.object_group = v1.werbemittel_id INNER JOIN ( SELECT wmax.object_group, MAX( wmax.object_revision ) wmaxobjrev FROM tblWerbemittel wmax GROUP BY wmax.object_group ) AS wmaxselect ON w1.object_group = wmaxselect.object_group AND w1.object_revision = wmaxselect.wmaxobjrev LEFT JOIN ( SELECT vmax.object_group, MAX( vmax.object_revision ) vmaxobjrev FROM tblVorgang vmax GROUP BY vmax.object_group ) AS vmaxselect ON v1.object_group = vmaxselect.object_group AND v1.object_revision = vmaxselect.vmaxobjrev LEFT JOIN tblWerbemittel_has_tblAngebot wha ON wha.werbemittel_id = w1.object_group LEFT JOIN tblAngebot ta ON ta.id = wha.angebot_id LEFT JOIN tblLieferanten tl ON tl.id = ta.lieferant_id AND wha.zuschlag = (SELECT MAX(zuschlag) FROM tblWerbemittel_has_tblAngebot WHERE werbemittel_id = w1.object_group) WHERE w1.flags =0 AND v1.flags=0; +--------+ | AMOUNT | +--------+ | 1982 | +--------+ 1 row in set (1.30 sec) Some indexes has been already set and as EXPLAIN shows they were used. +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2072 | | | 1 | PRIMARY | v1 | ref | werbemittel_group,werbemittel_id_index | werbemittel_group | 4 | wmaxselect.object_group | 2 | Using where | | 1 | PRIMARY | <derived3> | ALL | NULL | NULL | NULL | NULL | 3376 | | | 1 | PRIMARY | w1 | eq_ref | object_revision,or_og_index | object_revision | 8 | wmaxselect.wmaxobjrev,wmaxselect.object_group | 1 | Using where | | 1 | PRIMARY | wha | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 1 | PRIMARY | ta | eq_ref | PRIMARY | PRIMARY | 4 | dpd.wha.angebot_id | 1 | | | 1 | PRIMARY | tl | eq_ref | PRIMARY | PRIMARY | 4 | dpd.ta.lieferant_id | 1 | Using index | | 4 | DEPENDENT SUBQUERY | tblWerbemittel_has_tblAngebot | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 3 | DERIVED | vmax | index | NULL | object_revision_uq | 8 | NULL | 4668 | Using index; Using temporary; Using filesort | | 2 | DERIVED | wmax | range | NULL | or_og_index | 4 | NULL | 2168 | Using index for group-by | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ 10 rows in set (0.01 sec) The main problem while the statement above takes about 2 seconds seems to be the subselect where no index can be used. How to write the statement even more faster? Thanks for help. MT

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  • a way to use log4j pass values like java -DmyEnvVar=A_VALUE to my code

    - by raticulin
    I need to pass some value to enable certain code in may app (in this case is to optionally enable writing some stats to a file in certain conditions, but it might be anything generally). My java app is installed as a service. So every way I have thought of has some drawbacks: Add another param to main(): cumbersome as customers already have the tool installed, and the command line would need to be changed every time. Adding java -DmyEnvVar=A_VALUE to my command line: same as above. Set an environment variable: service should at least be restarted, and even then you must take care of what user is the service running under etc. Adding the property in the config file: I prefer not to have this visible on the config file so the user does not see it, it is something for debugging etc. So I thought maybe there is some way (or hack) to use log4j loggers to pass that value to my code. I have thought of one way already, although is very limited: Add a dummy class to my codebase com.dummy.DevOptions public class DevOptions { public static final Logger logger = Logger.getLogger(DevOptions.class); In my code, use it like this: if (DevOptions.logger.isInfoEnabled()){ //do my optional stuff } //... if (DevOptions.logger.isDebugEnabled()){ //do other stuff } This allows me to use discriminate among various values, and I could increase the number by adding more loggers to DevOptions. But I wonder whether there is a cleaner way, possibly by configuring the loggers only in log4j.xml??

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  • Variable not accessible within an if statment

    - by Chris
    I have a variable which holds a score for a game. My variable is accessible and correct outside of an if statement but not inside as shown below score is declared at the top of the main.cpp and calculated in the display function which also contains the code below cout << score << endl; //works if(!justFinished){ cout << score << endl; // doesn't work prints a large negative number endTime = time(NULL); ifstream highscoreFile; highscoreFile.open("highscores.txt"); if(highscoreFile.good()){ highscoreFile.close(); }else{ std::ofstream outfile ("highscores.txt"); cout << score << endl; outfile << score << std::endl; outfile.close(); } justFinished = true; } cout << score << endl;//works

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  • Small openmp programm freezes sometimes (gcc, c, linux)

    - by osgx
    Hello Just write a small omp test, and it does not work correctly all the times: #include <omp.h> int main() { int i,j=0; #pragma omp parallel for(i=0;i<1000;i++) { #pragma omp barrier j+= j^i; } return j; } The usage of j for writing from all threads is incorrect in this example, BUT there must be only nondeterministic value of j I have a freeze. Compiled with gcc-4.3.1 -fopenmp a.c -o gcc -static Run on 4-core x86_Core2 Linux server: $ ./gcc and got freeze (sometimes; like 1 freeze for 4-5 fast runs). Strace: [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] <... futex resumed> ) = 0 [pid 13119] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13120] futex(0x80cd798, FUTEX_WAIT, 1, NULL <unfinished ...> [pid 13109] <... futex resumed> ) = 0 [pid 13109] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13109] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13119] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13119] futex(0x80d3014, FUTEX_WAKE, 1) = 0 [pid 13119] futex(0x80d3020, FUTEX_WAIT, 251, NULL <freeze> Why do I have a freeze (deadlock)?

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  • C ++ virtual function

    - by user2950788
    masters of C++. I am trying to implement polymorphism in C++. I want to write a base class with a virtual function and then redefine that function in the child class. then demonstrate dynamic binding in my driver program. But I just couldn't get it to work. I know how to do it in C#, so I figured that I might have made some syntactical mistakes where I had used C#'s syntax in my C++ code, but these mistakes are not obvious to me at all. So I'd greatly appreciate it if you would correct my mistakes. class polyTest { public: polyTest(); virtual void type(); virtual ~polyTest(); }; void polyTest::type() { cout << "first gen"; } class polyChild: public polyTest { public: void type(); }; void polyChild::type() { cout << "second gen"; } int main() { polyChild * ptr1; polyChild * ptr2; ptr1 = new polyTest(); ptr2 = new polyChild(); ptr1 -> type(); ptr2 -> type(); }

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  • MS Exam 70-536 - How to throw and handle exception from thread?

    - by Max Gontar
    Hello! In MS Exam 70-536 .Net Foundation, Chapter 7 "Threading" in Lesson 1 Creating Threads there is a text: Be aware that because the WorkWithParameter method takes an object, Thread.Start could be called with any object instead of the string it expects. Being careful in choosing your starting method for a thread to deal with unknown types is crucial to good threading code. Instead of blindly casting the method parameter into our string, it is a better practice to test the type of the object, as shown in the following example: ' VB Dim info As String = o as String If info Is Nothing Then Throw InvalidProgramException("Parameter for thread must be a string") End If // C# string info = o as string; if (info == null) { throw InvalidProgramException("Parameter for thread must be a string"); } So, I've tried this but exception is not handled properly (no console exception entry, program is terminated), what is wrong with my code (below)? class Program { static void Main(string[] args) { Thread thread = new Thread(SomeWork); try { thread.Start(null); thread.Join(); } catch (InvalidProgramException ex) { Console.WriteLine(ex.Message); } finally { Console.ReadKey(); } } private static void SomeWork(Object o) { String value = (String)o; if (value == null) { throw new InvalidProgramException("Parameter for "+ "thread must be a string"); } } } Thanks for your time!

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  • My java program seems to be skipping over the try{}, executing the catch{} and then throwing a NullPointerException. What should I do?

    - by Matt Bolopue
    I am writing a program that calculates the number of words, syllables, and sentences in any given text file. I don't need help finding those numbers, however my program (which currently should only find the number of words in the text file) will not import the text file even when I type in the name of the file correctly. The text file is in the same folder as the source code. Instead it tells me every time that what I typed in has the wrong file extension (see my catch{}) and then proceeds to throw a null pointer. I am at a loss for what could be causing it. Any suggestions? import java.io.*; import java.util.*; public class Reading_Lvl_Calc { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub int words = 0; String fileName; Scanner scan; Scanner keyread = new Scanner(System.in); System.out.println("Please enter a file name (or QUIT to exit)"); fileName = keyread.nextLine(); File doc = new File(fileName); //while(scan.equals(null)){ try { scan = new Scanner(doc); } catch(Exception e) { if(fileName.substring(fileName.indexOf(".")) != ".txt") System.out.println("I'm sorry, the file \"" + fileName + "\" has an invalid file extension."); else System.out.println("I am sorry, the file \"" + fileName + " \" cannot be found.\n The file must be in the same directory as this program"); scan = null; } // } while(scan.hasNext()){ words++; scan.next(); } System.out.println(words); } }

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  • Static member function pointer to hold non static member function

    - by user1425406
    This has defeated me. I want to have a static class variable which is a pointer to a (non-static) member function. I've tried all sorts of ways, but with no luck (including using typedefs, which just seemed to give me a different set of errors). In the code below I have the static class function pointer funcptr, and I can call it successfully from outside the class, but not from within the member function CallFuncptr - which is what I want to do. Any suggestions? #include <stdio.h> class A { public: static int (A::*funcptr)(); int Four() { return 4;}; int CallFuncptr() { return (this->*funcptr)(); } // doesn't link - undefined reference to `A::funcptr' }; int (A::*funcptr)() = &A::Four; int main() { A fred; printf("four? %d\n", (fred.*funcptr)()); // This works printf("four? %d\n", fred.CallFuncptr()); // But this is the way I want to call it }

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  • Multiple column subselect in mysql 5 (5.1.42)

    - by rubber boots
    This one seems to be a simple problem, but I can't make it work in a single select or nested select. Retrieve the authors and (if any) advisers of a paper (article) into one row. I order to explain the problem, here are the two data tables (pseudo) papers (id, title, c_year) persons (id, firstname, lastname) plus a link table w/one extra attribute (pseudo): paper_person_roles( paper_id person_id act_role ENUM ('AUTHOR', 'ADVISER') ) This is basically a list of written papers (table: papers) and a list of staff and/or students (table: persons) An article my have (1,N) authors. An article may have (0,N) advisers. A person can be in 'AUTHOR' or 'ADVISER' role (but not at the same time). The application eventually puts out table rows containing the following entries: TH: || Paper_ID | Author(s) | Title | Adviser(s) | TD: || 21334 |John Doe, Jeff Tucker|Why the moon looks yellow|Brown, Rayleigh| ... My first approach was like: select/extract a full list of articles into the application, eg.SELECT q.id, q.title FROM papers AS q ORDER BY q.c_year and save the results of the query into an array (in the application). After this step, loop over the array of the returned information and retrieve authors and advisers (if any), via prepared statement (? is the paper's id) from the link table like:APPLICATION_LOOP(paper_ids in array) SELECT p.lastname, p.firstname, r.act_role FROM persons AS p, paper_person_roles AS r WHERE p.id=r.person_id AND r.paper_id = ? # The application does further processing from here (pseudo): foreach record from resulting records if record.act_role eq 'AUTHOR' then join to author_column if record.act_role eq 'ADVISER' then join to avdiser_column end print id, author_column, title, adviser_column APPLICATION_LOOP This works so far and gives the desired output. Would it make sense to put the computation back into the DB? I'm not very proficient in nontrivial SQL and can't find a solution with a single (combined or nested) select call. I tried sth. like SELECT q.title (CONCAT_WS(' ', (SELECT p.firstname, p.lastname AS aunames FROM persons AS p, paper_person_roles AS r WHERE q.id=r.paper_id AND r.act_role='AUTHOR') ) ) AS aulist FROM papers AS q, persons AS p, paper_person_roles AS r in several variations, but no luck ... Maybe there is some chance? Thanks in advance r.b.

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  • Calling NSFetchedResultsController & CoreData experts

    - by JK
    I am having a few nagging issues with NSFetchedResultsController and CoreData, any of which I would be very grateful to get help on. Issue 1 - Updates: I update my store on a background thread which results in certain rows being delete, inserted or updated. The changes are merged into the context on the main thread using the "mergeChangesFromContextDidSaveNotification:" method. Inserts and deletes are updated properly, but updates are not (e.g. the cell label is not updated with the change) although I have confirmed the updates to come through the contextDidSaveNotifcation, exactly like the inserts and deleted. My current workaround is to temporarily change the staleness interval of the context to 0, but this does not seem like the ideal solution. Issue 2 - Deleting objects: My fetch batch size is 20. If an object is deleted by the background thread which is in the first 20 rows, everything works fine. But if the object is after the first 20 rows and the table is scrolled down, a "CoreData could not fulfill a fault" error is raised. I have tried resaving the context and reperforming the frc fetch - all to no avail. Note: In this scenario, the frc delegate method "didChangeObject...." is not called for the delete - I assume this is because the object in question had not been faulted at that time (as it is was outside the initial fetch range). But for some reason, the context still thinks the object is around, although is has been deleted from the store. Issue 3 - Deleting sections : When the deletion of a row leads to the deletion of a section, I have gotten the "invalid number of rows in section???" error. I have worked around this by removing the "reloadSection" line from the NSFetchedResultsChangeMove: section and replacing it with "[tableView insertRowsAtIndexPaths...." This seems to work, but once again, I am not sure if this is the best solution. Any help would be greatly appreciated. Thank you!

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  • C++, generic programming and virtual functions. How do I get what I want?

    - by carleeto
    This is what I would like to do using templates: struct op1 { virtual void Method1() = 0; } ... struct opN { virtual void MethodN() = 0; } struct test : op1, op2, op3, op4 { virtual void Method1(){/*do work1*/}; virtual void Method2(){/*do work2*/}; virtual void Method3(){/*do work3*/}; virtual void Method4(){/*do work4*/}; } I would like to have a class that simply derives from a template class that provides these method declarations while at the same time making them virtual. This is what I've managed to come up with: #include <iostream> template< size_t N > struct ops : ops< N - 1 > { protected: virtual void DoStuff(){ std::cout<<N<<std::endl; }; public: template< size_t i > void Method() { if( i < N ) ops<i>::DoStuff(); } //leaving out compile time asserts for brevity } struct test : ops<6> { }; int main( int argc, char ** argv ) { test obj; obj.Method<3>(); //prints 3 return 0; } However, as you've probably guessed, I am unable to override any of the 6 methods I have inherited. I'm obviously missing something here. What is my error? No, this isn't homework. This is curiosity.

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  • C#. Saving information about events and event handlers and removing handlers using this information

    - by Philipp
    I have an object which is creating several event handlers using lambda expressions, and I need to remove all handlers created in that object in one time. I'm trying to create some unified static object which will 'know' which handler relates to which object and event if event handler was created through this static object. I tried something like code below, but I don't understand how to save events and event handlers objects, to be able remove handlers in one time. class Program { static void Main(string[] args) { var EventSender = new EventSender(); var EventReceiver = new EventReceiver(EventSender); EventSender.Invoke(" some var "); LinkSaver.RemoveEvent(EventReceiver); // ?? Console.ReadKey(); } } public class ObjLink{ public object Event; public object Action; } public static class LinkSaver { public static void SetEvent<T>(object obj, Action<T> Event, T Action) { Event(Action); var objLink = new ObjLink{Event = Event, Action = Action}; if (!Links.ContainsKey(obj)) Links.Add(obj, new List<ObjLink>{objLink}); else Links[obj].Add(objLink); } static Dictionary<object,List<ObjLink>> Links = new Dictionary<object, List<ObjLink>>(); public static void RemoveEvent(object obj){ foreach(var objLink in Links[obj]){ // objLink.Event -= objLink.Action; ??? } } } public class EventReceiver { public EventReceiver(EventSender obj) { LinkSaver.SetEvent<EventSender.TestDelegate>(this, obj.SetEvent, str => Console.WriteLine(str + " test event!")); } } public class EventSender { public void Invoke(string var) { if (eventTest != null) eventTest(var); } public void SetEvent(TestDelegate Action) { eventTest += Action; } public delegate void TestDelegate(string var); private event TestDelegate eventTest; // by the way public void RemoveFromEvent() { foreach (var handler in eventTest.GetInvocationList()) eventTest -= (TestDelegate)handler; } }

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  • Java: over-typed structures?

    - by HH
    Term over-type structure = a data structure that accepts different types, can be primitive or user-defined. I think ruby supports many types in structures such as tables. I tried a table with types 'String', 'char' and 'File' in Java but errs. How can I have over-typed structure in Java? How to show types in declaration? What about in initilization? Suppose a structure: INDEX VAR FILETYPE //0 -> file FILE //1 -> lineMap SizeSequence //2 -> type char //3 -> binary boolean //4 -> name String //5 -> path String Code import java.io.*; import java.util.*; public class Object { public static void print(char a) { System.out.println(a); } public static void print(String s) { System.out.println(s); } public static void main(String[] args) { Object[] d = new Object[6]; d[0] = new File("."); d[2] = 'T'; d[4] = "."; print(d[2]); print(d[4]); } } Errors Object.java:18: incompatible types found : java.io.File required: Object d[0] = new File("."); ^ Object.java:19: incompatible types found : char required: Object d[2] = 'T'; ^

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  • C++ polymorphism and slicing

    - by Draco Ater
    The following code, prints out Derived Base Base But I need every Derived object put into User::items, call its own print function, but not the base class one. Can I achieve that without using pointers? If it is not possible, how should I write the function that deletes User::items one by one and frees memory, so that there should not be any memory leaks? #include <iostream> #include <vector> #include <algorithm> using namespace std; class Base{ public: virtual void print(){ cout << "Base" << endl;} }; class Derived: public Base{ public: void print(){ cout << "Derived" << endl;} }; class User{ public: vector<Base> items; void add_item( Base& item ){ item.print(); items.push_back( item ); items.back().print(); } }; void fill_items( User& u ){ Derived d; u.add_item( d ); } int main(){ User u; fill_items( u ); u.items[0].print(); }

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  • How to get attribute value using SelectSingleNode in C#?

    - by Nano HE
    Hello. I am parsing a xml document, I need find out the gid (an attribute) value (3810). Based on SelectSingleNode(). I found it is not easy to find the attribute name and it's value. Can I use this method or I must switch to other way. Attached my code. How can I use book obj to get the attribute value3810 for gid. Thank you. My test.xml file as below <?xml version="1.0"?> <root> <VersionInfo date="2007-11-28" version="1.0.0.2"/> <Attributes> <AttrDir name="EFEM" DirID="1"> <AttrDir name="Aligner" DirID="2"> <AttrDir name="SequenceID" DirID="3"> <AttrObj text="Slot01" gid="3810" unit="" scale="1"/> <AttrObjCount value="1"/> </AttrDir> </AttrDir> </AttrDir> </Attributes> </root> I wrote the test.cs as below public class Sample { public static void Main() { XmlDocument doc = new XmlDocument(); doc.Load("test.xml"); XmlNode book; XmlNode root = doc.DocumentElement; book = root.SelectSingleNode("Attributes[AttrDir[@name='EFEM']/AttrDir[@name='Aligner']/AttrDir[@name='SequenceID']/AttrObj[@text='Slot01']]"); Console.WriteLine("Display the modified XML document...."); doc.Save(Console.Out); } }

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