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• how to access child instances in a vector in c++

  - by tsubasa

  I have a parent class and child class (inherited from parent). In the child class, I have a member function named function_blah(); I used vector<parent*> A to store 5 parent instances, 3 child instances. So the total number of elements in the vector is 8. I can easily access to member functions of element A[0] to A[4], which are parent instances. But whenever I try to have access to member functions of element A[5] to A[7], the compiler complains that class parent has no member named 'function_blah' The way I access to elements is using index. e.x A[i] with i = 0..7. Is it correct? if not, how?

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• How to pass a function to a function?

  - by ShaChris23

  Suppose I have a class with 2 static functions: class CommandHandler { public: static void command_one(Item); static void command_two(Item); }; I have a problem DRY problem where I have 2 functions that have the exact same code for every single line, except for the function that it calls: void CommandOne_User() { // some code A CommandHandler::command_one(item); // some code B } void CommandTwo_User() { // some code A CommandHandler::command_two(item); // some code B } I would like to remove duplication, and, ideally, do something like this: void CommandOne_User() { Function func = CommandHandler::command_one(); Refactored_CommandUser(func); } void CommandTwo_User() { Function func = CommandHandler::command_one(); Refactored_CommandUser(func); } void Refactored_CommandUser(Function func) { // some code A func(item); } I have access to Qt, but not Boost. Could someone help suggest a way on how I can refactor something like this?

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• Is this a good approach to execute a list of operations on a data structure in Python?

  - by Sridhar Iyer

  I have a dictionary of data, the key is the file name and the value is another dictionary of its attribute values. Now I'd like to pass this data structure to various functions, each of which runs some test on the attribute and returns True/False. One approach would be to call each function one by one explicitly from the main code. However I can do something like this: #MYmodule.py class Mymodule: def MYfunc1(self): ... def MYfunc2(self): ... #main.py import Mymodule ... #fill the data structure ... #Now call all the functions in Mymodule one by one for funcs in dir(Mymodule): if funcs[:2]=='MY': result=Mymodule.__dict__.get(funcs)(dataStructure) The advantage of this approach is that implementation of main class needn't change when I add more logic/tests to MYmodule. Is this a good way to solve the problem at hand? Are there better alternatives to this solution?

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• Extensions methods and forward compatibilty of source code.

  - by TcKs

  Hi, I would like solve the problem (now hypothetical but propably real in future) of using extension methods and maginification of class interface in future development. Example: /* the code written in 17. March 2010 */ public class MySpecialList : IList<MySpecialClass> { // ... implementation } // ... somewhere elsewhere ... MySpecialList list = GetMySpecialList(); // returns list of special classes var reversedList = list.Reverse().ToList(); // .Reverse() is extension method /* now the "list" is unchanged and "reveresedList" has same items in reversed order */ /* --- in future the interface of MySpecialList will be changed because of reason XYZ*/ /* the code written in some future */ public class MySpecialList : IList<MySpecialClass> { // ... implementation public MySpecialList Reverse() { // reverse order of items in this collection return this; } } // ... somewhere elsewhere ... MySpecialList list = GetMySpecialList(); // returns list of special classes var reversedList = list.Reverse().ToList(); // .Reverse() was extension method but now is instance method and do something else ! /* now the "list" is reversed order of items and "reveresedList" has same items lake in "list" */ My question is: Is there some way how to prevent this case (I didn't find them)? If is now way how to prevent it, is there some way how to find possible issues like this? If is now way how to find possible issues, should I forbid usage of extension methods? Thanks.

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• Deleting unneeded rows from a table with 2 criteria

  - by stormbreaker

  Hello. I have a many-to-many relations table and I need to DELETE the unneeded rows. The lastviews table's structure is: | user (int) | document (int) | time (datetime) | This table logs the last users which viewed the document. (user, document) is unique. I show only the last 10 views of a document and until now I deleted the unneeded like this: DELETE FROM `lastviews` WHERE `document` = ? AND `user` NOT IN (SELECT * FROM (SELECT `user` FROM `lastviews` WHERE `document` = ? ORDER BY `time` DESC LIMIT 10) AS TAB) However, now I need to also show the last 5 documents a user has viewed. This means I can no longer delete rows using the previous query because it might delete information I need (say a user didn't view documents in 5 minutes and the rows are deleted) To sum up, I need to delete all the records that don't fit these 2 criterias: SELECT ... FROM `lastviews` WHERE `document` = ? ORDER BY `time` DESC LIMIT 10 and SELECT * FROM `lastviews` WHERE `user` = ? ORDER BY `time` DESC LIMIT 0, 5 I need the logic. Thanks in advance.

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• if else-if making code look ugly any cleaner solution?

  - by Vishal

  I have around 20 functions (is_func1, is_fucn2, is_func3...) returning boolean I assume there is only one function which returns true and I want that! I am doing: if is_func1(param1, param2): # I pass 1 to following abc(1) # I pass 1 some_list.append(1) elif is_func2(param1, param2): # I pass 2 to following abc(2) # I pass 1 some_list.append(2) ... . . elif is_func20(param1, param2): ... Please note: param1 and param2 are different for each, abc and some_list take parameters depending on the function. The code looks big and there is repetition in calling abc and some_list, I can pull this login in a function! but is there any other cleaner solution? I can think of putting functions in a data structure and loop to call them.

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• Limiting database security

  - by Torbal

  A number of texts signify that the most important aspects offered by a DBMS are availability, integrity and secrecy. As part of a homework assignment I have been tasked with mentioning attacks which would affect each aspect. This is what I have come up with - are they any good? Availability - DDOS attack Integrity Secrecy - SQL Injection attack Integrity - Use of trojans to gain access to objects with higher security roles

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• c# programs..multiplication of strings with n numbers and display it.

  - by smitha

  I want to multiply strings using functions.with user giving the string and the power to that string.and display it.

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• Efficient retrieval of lists over WebServices

  - by Chris

  I have a WCF WebService that uses LINQ and EF to connect to an SQL database. I have an ASP.NET MVC front end that collects its data from the webservice. It currently has functions such as List<Customer> GetCustomers(); As the number of customers increases massively the amount of data being passed increases also reducing efficiency. What is the best way to "page data" across WebServices etc. My current idea is to implement a crude paging system such as List<Customer> GetCustomers(int start, int length); This, however, means I would have to replicate such code for all functions returning List types. It is unfortunate that I cannot use LINQ as it would be much nicer. Does anyone have any advice or ideas of patterns to implement that would be "as nice as possible" Thanks

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• Is it OK to put a standard, pure C header #include directive inside a namespace?

  - by mic_e

  I've got a project with a class log in the global namespace (::log). So, naturally, after #include <cmath>, the compiler gives an error message each time I try to instantiate an object of my log class, because <cmath> pollutes the global namespace with lots of three-letter methods, one of them being the logarithm function log(). So there are three possible solutions, each having their unique ugly side-effects. Move the log class to it's own namespace and always access it with it's fully qualified name. I really want to avoid this because the logger should be as convenient as possible to use. Write a mathwrapper.cpp file which is the only file in the project that includes <cmath>, and makes all the required <cmath> functions available through wrappers in a namespace math. I don't want to use this approach because I have to write a wrapper for every single required math function, and it would add additional call penalty (cancelled out partially by the -flto compiler flag) The solution I'm currently considering: Replace #include <cmath> by namespace math { #include "math.h" } and then calculating the logarithm function via math::log(). I have tried it out and it does, indeed, compile, link and run as expected. It does, however, have multiple downsides: It's (obviously) impossible to use <cmath>, because the <cmath> code accesses the functions by their fully qualified names, and it's deprecated to use in C++. I've got a really, really bad feeling about it, like I'm gonna get attacked and eaten alive by raptors. So my question is: Is there any recommendation/convention/etc that forbid putting include directives in namespaces? Could anything go wrong with diferent C standard library implementations (I use glibc), different compilers (I use g++ 4.7, -std=c++11), linking? Have you ever tried doing this? Are there any alternate ways to banish the math functions from the global namespace? I've found several similar questions on stackoverflow, but most were about including other C++ headers, which obviously is a bad idea, and those that weren't made contradictory statements about linking behaviour for C libraries. Also, would it be beneficial to additionally put the #include <math.h> inside extern "C" {}?

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• Oracle Query Optimization: Why is My Second Query Faster?

  - by Patrick Cuff

  I was having some performance issues with an Oracle query, so I downloaded a trial of the Quest SQL Optimizer for Oracle, which made some changes that dramatically improved the query's performance. I'm not exactly sure why the recommended query had such an improvement; can anyone provide an explanation? Before: SELECT t1.version_id, t1.id, t2.field1, t3.person_id, t2.id FROM table1 t1, table2 t2, table3 t3 WHERE t1.id = t2.id AND t1.version_id = t2.version_id AND t2.id = 123 AND t1.version_id = t3.version_id AND t1.VERSION_NAME <> 'AA' order by t1.id Plan Cost: 831 Elapsed Time: 00:00:21.40 Number of Records: 40,717 After: SELECT /*+ USE_NL_WITH_INDEX(t1) */ t1.version_id, t1.id, t2.field1, t3.person_id, t2.id FROM table2 t2, table3 t3, table1 t1 WHERE t1.id = t2.id + 0 AND t1.version_id = t2.version_id + 0 AND t2.id = 123 AND t1.version_id = t3.version_id + 0 AND t1.VERSION_NAME || '' <> 'AA' AND t3.version_id = t2.version_id + 0 order by t1.id Plan Cost: 686 Elapsed Time: 00:00:00.95 Number of Records: 40,717 Questions: Why does re-arranging the order of the tables in the FROM clause help? Why does adding + 0 to the WHERE clause comparisons help? Why does || '' <> 'AA' in the WHERE clause VERSION_NAME comparison help? Is this a more efficient way of handling possible nulls on this column?

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• maching strings

  - by kiran

  Write two functions, called countSubStringMatch and countSubStringMatchRecursive that take two arguments, a key string and a target string. These functions iteratively and recursively count the number of instances of the key in the target string. You should complete definitions for def countSubStringMatch(target,key): and def countSubStringMatchRecursive (target, key): For the remaining problems, we are going to explore other substring matching ideas. These problems can be solved with either an iterative function or a recursive one. You are welcome to use either approach, though you may find iterative approaches more intuitive in these cases of matching linear structures.

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• Angularjs code/naming conventions

  - by Dalorzo

  Does anyone know if exists any official or most accepted reference for Angular naming conventions to use when we build our applications? Angular has a lot of different type of components such as filters, directives, services and so on. Wouldn't you agree that having a reference naming convention when we implement them in our applications will make sense? For example: If we need to create new filters how should we name them like [Something]Filter or filter[Something] or something else? And same applies for Controllers, Services, Directives and so on. Other things I wonder about is if variables/functions that belongs to the scope should have an special prefix or suffix. In some situations it may be useful to have a way to differentiate them from functions and other (none angular code).

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• Unicode string handling using Windows API

  - by DeadMG

  I always assumed that Unicode string handling was some dark art. However, I've seen that the Windows API has functions for comparing Unicode strings, for example. Does that mean that it's actually feasible to write a Unicode string class that can perform simple actions like sorting, equality comparison, and extraction from a file? Or are there hidden gotchas in the use of these functions that makes it actually a really bad idea? I'm just looking at libraries like ICU and they seem incredibly over-complicated compared to what a Unicode string class backed by the Windows API could actually look like, which would resemble the Standard string classes quite closely.

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• CakePHP - Paginating an Array

  - by Ashok

  Cake handles pagination of a model with a simple $this-paginate(), but what should I use if I want to paginate a array of values? The Scenario is like this: $this->set('sitepages', $this->paginate()); This code in my index() returns an array like Array ( [0] => Array ( [Sitepage] => Array ( [id] => 13 [name] => Home [urlslug] => home [parent_id] => 1 [page_title] => Welcome to KIAMS, Pune [order] => 1 ) ) [1] => Array ( [Sitepage] => Array ( [id] => 26 [name] => About Us [urlslug] => aboutus [parent_id] => 1 [page_title] => [order] => 2 ) ) [2] => Array ( [Sitepage] => Array ( [id] => 27 [name] => Overview of KIAMS [urlslug] => aboutus/overview [parent_id] => 26 [page_title] => [order] => 2 ) ) I retrieved the same data using $this-Sitepage-find('all') and then performed some manipulations as required and form a array which is very similar to the above one, but the ordering gets changed. I want to paginate this new array and pass it to the view. I tried $this->set('sitepages',$this->paginate($newarray)) But the data is not getting paginated. Can some one please help with paginating the $newarray in CakePHP?

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• Can pydoc/help() hide the documentation for inherited class methods and attributes?

  - by EOL

  When declaring a class that inherits from a specific class: class C(dict): added_attribute = 0 the documentation for class C lists all the methods of dict (either through help(C) or pydoc). Is there a way to hide the inherited methods from the automatically generated documentation (the documentation string can refer to the base class, for non-overwritten methods)? or is it impossible? This would be useful: pydoc lists the functions defined in a module after its classes. Thus, when the classes have a very long documentation, a lot of less than useful information is printed before the new functions provided by the module are presented, which makes the documentation harder to exploit (you have to skip all the documentation for the inherited methods until you reach something specific to the module being documented).

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• Wordpress SQL_CALC fix causes PHP error

  - by ok1ha

  I'm looking for some followup on an older topic for Wordpress where SQL_CALC was found to slow things down when you have a large DB in Wordpress. I have been using the code, at the bottom of this post, to get around it but it does generate an error in my error log. How would I prevent this error? PHP Warning: Division by zero in /var/www/vhosts/domain.com/httpdocs/wp-content/themes/greatTheme/functions.php on line 19 The original thread: http://wordpress.org/support/topic/slow-queries-sql_calc_found_rows-bringing-down-site?replies=25 The code in my functions.php: add_filter('pre_get_posts', 'optimized_get_posts', 100); function optimized_get_posts() { global $wp_query, $wpdb; $wp_query->query_vars['no_found_rows'] = 1; $wp_query->found_posts = $wpdb->get_var( "SELECT COUNT(*) FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private')" ); $wp_query->found_posts = apply_filters_ref_array( 'found_posts', array( $wp_query->found_posts, &$wp_query ) ); $wp_query->max_num_pages = ceil($wp_query->found_posts / $wp_query->query_vars['posts_per_page']); return $wp_query; }

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• How do I get the icons of TinyMCE to show?

  - by ggfan

  I installed TinyMCE and I have the textbox and the functions work(such as , ) but I don't see the tool box that has displays all the functions. Like in this example. How do I get the images to show? All I have is the textbox. I used the code from the example link and theirs has the images and all I have is the textbox. What part do I edit to be able to see the icons? //my source link <script type="text/javascript" src="/tinymce/jscripts/tiny_mce/tiny_mce.js"> tinyMCE.init({ // Example content CSS (should be your site CSS) content_css : "style12.css", // Drop lists for link/image/media/template dialogs template_external_list_url : "/tinymce/examples/lists/template_list.js", external_link_list_url : "/tinymce/examples/lists/link_list.js", external_image_list_url : "/tinymce/examples/lists/image_list.js", media_external_list_url : "/tinymce/examples/lists/media_list.js",

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• C/C++ function definitions without assembly

  - by Jack

  Hi, I always thought that functions like printf() are in the last step defined using inline assembly. That deep into stdio.h is burried some asm code that actually tells CPU what to do. Something like in dos, first mov bagining of the string to some memory location or register and than call some int. But since x64 version of Visual Studio doesent support inline assembler at all, it made me think that there are really no assembler-defined functions in C/C++. So, please, how is for example printf() defined in C/C++ without using assembler code? What actually executes the right software interrupt? Thanks.

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• Create object of unknown class (two inherited classes)

  - by Paul

  I've got the following classes: class A { void commonFunction() = 0; } class Aa: public A { //Some stuff... } class Ab: public A { //Some stuff... } Depending on user input I want to create an object of either Aa or Ab. My imidiate thought was this: A object; if (/*Test*/) { Aa object; } else { Ab object; } But the compiler gives me: error: cannot declare variable ‘object’ to be of abstract type ‘A’ because the following virtual functions are pure within ‘A’: //The functions... Is there a good way to solve this?

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• Heap Algorithmic Issue

  - by OberynMarDELL

  I am having this algorithmic problem that I want to discuss about. Its not about find a solution but about optimization in terms of runtime. So here it is: Suppose we have a race court of Length L and a total of N cars that participate on the race. The race rules are simple. Once a car overtakes an other car the second car is eliminated from the race. The race ends when no more overtakes are possible to happen. The tricky part is that the k'th car has a starting point x[k] and a velocity v[k]. The points are given in an ascending order, but the velocities may differ. What I've done so far: Given that a car can get overtaken only by its previous, I calculated the time that it takes for each car to reach its next one t = (x[i] - x[i+1])/(v[i] - v[i+1]) and I insert these times onto a min heap in O(n log n). So in theory I have to pop the first element in O(logn), find its previous, pop it as well , update its time and insert it in the heap once more, much like a priority queue. My main problem is how I can access specific points of a heap in O(log n) or faster in order to keep the complexity in O(n log n) levels. This program should be written on Haskell so I would like to keep things simple as far as possible EDIT: I Forgot to write the actual point of the race. The goal is to find the order in which cars exit the game

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• How do I get regex support in excel via a function, or custom function?

  - by blunders

  It appears that regex (as in regular expressions) is not supported in excel, except via VBA. Is this so, and is it is, are there any "open source" custom VBA functions that support regex. In this case I'm looking to extract complex pattern within a string, but any implementation of a custom VBA function that expose support of regex within the function itself would be of use. If you know of semi-related function such as the IS function, feel feel to comment, though I'm really looking for a full regular expression implementation that is exposed via functions. Might even be open to a pay to use add-in if the implementation is good. If you have questions, please comment.

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• Why the streams in C++?

  - by oh boy

  As you all know there are libraries using streams such as iostream and fstream. My question is: Why streams? Why didn't they stick with functions similar to print, fgets and so on (for example)? They require their own operators << and >> but all they do could be implemented in simple functions like above, also the function printf("Hello World!"); is a lot more readable and logical to me than cout << "Hello World"; I also think that all of those string abstractions in C++ all compile down to (less efficient) standard function calls in binary.

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• Noob question: Draw a quad parallel to the view.

  - by Jack

  Hi all, ok what I want to do is to draw a quad in the scene that lays on a plane parallel to the view. So it should appear flat. More in particular, I think I didn't get very well how the mechanism of gluLookAt works in comparison with the functions glTranslate and glRotate: If I position the view "manually" using the functions glTranslate and glRotate whenever I draw an object its position is relative to the current view. And I understand that this is due to the transformation matrix in the stack. However when I use the gluLookAt that should automatically set the view, the coordinates of the object I want to draw must be "absolute" to show it properly. Thanks in advance.

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• PHP, since upgrading to 5.2.17 getting some warning ?

  - by Jules

  I can't reproduce this on my test server no idea why this is happening, other queries / functions work.. I'm getting this warning PHP Warning: mysql_connect() [<a href='function.mysql-connect'> function.mysql-connect</a>]: Can't connect to MySQL server on '--my isps server--' (10060) in D:\domains\mydomain.com\wwwroot\p hp\_stdfuncs.php on line 191 This function and others like it are having problems (but some are ok), this is my include file... function AddPageError($PageHandle, $Requested) { global $server; global $db; global $user; global $pass; global $sDebug; $con = mysql_connect($server,$user,$pass); I have an include file which sets those variables, as I say they work on other pages and functions.. No idea why ??

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