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  • Why I have to redeclare a virtual function while overriding [C++]

    - by Neeraj
    #include <iostream> using namespace std; class Duck { public: virtual void quack() = 0; }; class BigDuck : public Duck { public: // void quack(); (uncommenting will make it compile) }; void BigDuck::quack(){ cout << "BigDuckDuck::Quack\n"; } int main() { BigDuck b; Duck *d = &b; d->quack(); } Consider this code, the code doesn't compiles. However when I declare the virtual function in the subclass, then it compiles fine. The compiler already has the signature of the function which the subclass will override, then why a redeclaration is required? Any insights.

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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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  • jQuery .toggle() not working as expected with second function?!

    - by Christopher
    I'm trying to create a button to show / hide a div below it, all is working fine, I'm just struggling with the last bit! I need to distinguish wether it's a show or hide action so I can pass the variable elsewhere, here's what I have.. $(this).find('.hide-close').click( function() { $(this).siblings('.dragbox-content').toggle(function() { alert($(this).parent().attr("id") + ' Show'); },function() { alert($(this).parent().attr("id") + ' Hide'); } ); }) .end() }); If use the following code, taking out the second function within toggle(), it works?! But then I don't have a show / hide variable. $(this).find('.hide-close').click( function() { $(this).siblings('.dragbox-content').toggle(function() { alert($(this).parent().attr("id") + ' Show'); } ); }) .end() }); Thanks in advance for any help, hopefully it's something really simple I just can't see! :)

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  • Dynamic SQL and Funtions

    - by Unlimited071
    Hi all, is there any way of accomplishing something like the following: CREATE FUNCTION GetQtyFromID ( @oricod varchar(15), @ccocod varchar(15), @ocmnum int, @oinnum int, @acmnum int, @acttip char(2), @unisim varchar(15) ) AS BEGIN DECLARE @Result decimal(18,8) DECLARE @SQLString nvarchar(max); DECLARE @ParmDefinition nvarchar(max); --I need to execute a query stored in a cell which returns the calculated qty. --i.e of AcuQry: select @cant = sum(smt) from table where oricod = @oricod and ... SELECT @SQLString = AcuQry FROM OinActUni WHERE (OriCod = @oricod) AND (ActTipCod = @acttip) AND (UniSim = @unisim) AND (AcuEst > 0) SET @ParmDefinition = N' @oricod varchar(15), @ccocod varchar(15), @ocmnum int, @oinnum int, @acmnum int, @cant decimal(18,8) output'; EXECUTE sp_executesql @SQLString, @ParmDefinition, @oricod = @oricod, @ccocod = @ccocod, @ocmnum = @ocmnum, @oinnum = @oinnum, @acmnum = @acmnum, @cant = @result OUTPUT; RETURN @Result END The problem with this approach is that it is prohibited to execute sp_excutesql in a function... What I need is to do something like: select id, getQtyFromID(id) as qty from table The main idea is to execute a query stored in a table cell, this is because the qty of something depends on it's unit. the unit can be days or it can be metric tons, so there is no relation between the units, therefore the need of a specific query for each unit.

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  • How to override virtual function in good style? [C++]

    - by Knowing me knowing you
    Hi, guys I know this question is very basic but I've met in few publications (websites, books) different style of override virtual function. What I mean is: if I have base class: class Base { public: virtual void f() = 0; }; in some publications I saw that to override this some authors would just say: void f(); and some would still repeat the virtual keyword before void. Which form of overwriting is in good style? Thank you for your answers.

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  • How to run jQuery onClick? Need to pass a variable to run .ajax

    - by user205307
    I'm trying to run .ajax and insert a data element from the onClick of an item from the page. Whats the best way to do this? Something like this: function grabinfo(foo){ $.ajax({ url: "infospitter", method: "GET", data: "id="+foo, success: function(html){ $(#showstuff).html(html); } }); } <input onClick="javascript:grabinfo(18343)" /> // and on page each item will have this button input

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  • PHP Array Not Working in Function

    - by lemonpole
    Hello all. I'm currently experimenting with arrays in PHP, and I created a fake environment where a team's information will be displayed. $t1 = array ( "basicInfo" => array ( "The Sineps", "December 25, 2010", "lemonpole" ), "overallRecord" => array (0, 0, 0, 0), "overallSeasons" => array ( 1 => array (14, 0, 0), 2 => array (9, 5, 2), 3 => array (12, 4, 0), 4 => array (3, 11, 2) ), "games" => array ( "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />" ), "seasonHistory" => array ( "Season I", "Season II", "Season III", "Season IV" ), "divisions" => array ( "Open", "Main", "Main", "Invite" ) ); // Displays the seasons the team has been in along // with the record of each season. function seasonHistory() { // Make array variable local-scope. global $t1; // Count the number of seasons. $numrows = count($t1["seasonHistory"]); // Loop through all the variables until // it reaches the last entry made and display // each item seperately. for($v = 0; $v <= $numrows; $v++) { // Echo each season. echo "<tr><td>{$t1["games"][$v]}</td>"; echo "<td>{$t1["seasonHistory"][$v]}</td>"; echo "<td>{$t1["divisions"][$v]}</td></tr>"; } } I have tested several possible problems out and after narrowing them down I have come down to one conclusion and that is my function is not connecting to the array for some reason. I don't know what else to do because I thought making the array global would fix that problem. What works: I can echo $t1["games"][0] on the page I need it to display and it gives me the content. I tried echo $t1["games"][0] INSIDE the function and then calling the function and it doesn't display anything.

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  • How to determine magnitude of trigonometric function? C++

    - by seaworthy
    > if (((test>=0) && (test<=90)) || ((test>270) && (test<=360))){n_y=1;} > else {n_y=-1;} I need the magnitude of trigonometric function in order to determine the sign of the trigonometric function for an angle falling into a particular quadrant. My plan is to replace the code above with something equivalent. Here is what I want to do in pseudo-code. n_y = cos(test) / (magnitude of cos (test)); This will give me same thing. Abs() only takes integers. Any help is appreciated.

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  • How with lambda function in MVC3

    - by doogdeb
    I have a model which contains view models for each view. This model is held in session and is initialised when application starts. I need to be able to populate a field from one view model with the value from another so have used a lambda function. Below is my model. I am using a lambda so that when I get Test2.MyProperty it will use the FunctionTestProperty to retrieve the value from Test1.TestProperty. public class Model { public Model() { Test1 = new Test1() Test2 = new Test2(FunctionTestProperty () => Test1.TestProperty) } } public class Test1 { public string TestProperty { get; set; } } public class Test2 { public Test2() : this (() => string.Empty) {} public Test2(Func<string> functionTestProperty) { FunctionTestProperty = functionTestProperty; } public Func<string> FunctionTestProperty { get; set; } public string MyProperty { get{ return FunctionTestProperty() ?? string.Empty; } } } This works perfectly when I first run the application and navigate from Test1 to Test2; I can see that when I get the value for MyProperty it calls back to Model constructor and retrieves the Test1.TestProperty value. However when I then submit the form (Test2) it calls the default constructor which sets it to string.Empty. So if I go back to Test1 and back to Test2 again it always then calls the Test2 default constructor. Does anyone know why this works when first running the application but not after the view is submitted, or if I have made an obvious mistake?

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  • What ways are there to edit a function in R?

    - by Tal Galili
    Let's say we have the following function: foo <- function(x) { line1 <- x line2 <- 0 line3 <- line1 + line2 return(line3) } And that we want to change the second line to be: line2 <- 2 How would you do that? One way is to use fix(foo) And change the function. Another way is to just write the function again. Is there another way? (Remember, the task was to change just the second line)

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  • PHP - Use isset inside function not working..?

    - by pnichols
    I have a PHP script that when loaded, check first if it was loaded via a POST, if not if GET['id'] is a number. Now I know I could do this like this: if(isset($_GET['id']) AND isNum($_GET['id'])) { ... } function isNum($data) { $data = sanitize($data); if ( ctype_digit($data) ) { return true; } else { return false; } } But I would like to do it this way: if(isNum($_GET['id'])) { ... } function isNum($data) { if ( isset($data) ) { $data = sanitize($data); if ( ctype_digit($data) ) { return true; } else { return false; } } else { return false; } } When I try it this way, if $_GET['id'] isn't set, I get a warning of undefined index: id... It's like as soon as I put my $_GET['id'] within my function call, it sends a warning... Even though my function will check if that var is set or not... Is there another way to do what I want to do, or am I forced to always check isset then add my other requirements..??

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  • Function callers in C?

    - by thyrgle
    So I was wondering how they work. To explain what I mean by a "function caller" a good example of what I mean would be glutTimerFunc, it is able to take in a function as a parameter and call it even with it not knowing it is declared. How is it doing this?

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  • When parsing XML with jquery, how can we pass the current node from within each() to another functio

    - by Johusa
    Say we have an XML document with many book nodes... When parsing XML with jquery, how can i pass the current node from each() iteration to another function that will do some stuff until something is reached and then go back to the previous function (passing along the current node from this function back to the first function)? Here something more descriptive (this is just an example out of my head, not accurate): function MyParser(x1,x2,dom) { // if i am called by anotherFunction(thisNode) proceed from the passed node dom.find('book').each(function() { var Letter = thisNode.find(author).charAt(0); if(x1 == Letter) { // print everything till the next letter (x2) anotherFunction(thisNode) } } } function anotherFunction(x2,thisNode) { //continue parsing here until you reached x2 //when x2 is reached, return to previous function passing again the current node }

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  • class T in c++ (your definition)

    - by JohnWong
    The one advantage of using class T in c++ is to reduce the time to redefine data types in a function, if those data types are defined in other function, for example, in int main. template <class T> void showabs(T number) { if (number < 0 ) number = -number; cout << number << endl; return 0; } int main() { int num1 = -4; float num2 = -4.23f; showabs(num1); showabs(num2); return 0; } So in this case, without class T, for each data type, we have to add its corresponding data-type condition, that is, another set of if statement for int, and another one for float. Am I correct?

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  • Can I use a method as a lambda?

    - by NewAlexandria
    I have an interface the defines a group of conditions. it is one of several such interfaces that will live with other models. These conditions will be called by a message queue handler to determine completeness of an alert. All the alert calls will be the same, and so I seek to DRY up the enqueue calls a bit, by abstracting the the conditions into their own methods (i question if methods is the right technique). I think that by doing this I will be able to test each of these conditions. class Loan module AlertTriggers def self.included(base) base.extend LifecycleScopeEnqueues # this isn't right Loan::AlertTriggers::LifecycleScopeEnqueues.instance_method.each do |cond| class << self def self.cond ::AlertHandler.enqueue_alerts( {:trigger => Loan.new}, cond ) end end end end end module LifecycleScopeEnqueues def student_awaiting_cosigner lambda { |interval, send_limit, excluding| excluding ||= '' Loan.awaiting_cosigner. where('loans.id not in (?)', excluding.map(&:id) ). joins(:petitions). where('petitions.updated_at > ?', interval.days.ago). where('petitions.updated_at <= ?', send_limit.days.ago) } end end I've considered alternatives, where each of these methods act like a scope. Down that road, I'm not sure how to have AlertHandler be the source of interval, send_limit, and excluding, which it passes to the block/proc when calling it.

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  • Are Objective-C function names stored in text?

    - by thyrgle
    I don't remember where I heard about it, (I think I was searching up on how selectors worked and it ended up not being exactly the same as a callback function) and I can't confirm it. But more importantly than that, is there a way I could get a list of the function names from another application?

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  • What are the useful UNIX functions that MS doesn't implement? And why? [closed]

    - by prosseek
    When programming with Python, I came across some functions that are not implemented on Windows. os.fork() may be one of them. UNIX came before WinNT, so the WinNT developers (most notably Dave Cutler) must knew about the features and functions of the UNIX. But, to me, it seems that MS didn't like UNIX so much that they mistakenly/intentionally skipped or distorted some of the useful UNIX functions/features; i.e. /abc/def in UNIX, \abc\def in Windows as an easy example. And when I read the Windows System Programming book, I felt uncomfortable as the Windows system functions seem nothing more than a tweak from UNIX. (I might be wrong.) What are those functions/features that MS OSes don't have, but UNIX origninated? Is there any reason for this? Do they just want to differentiate from UNIX world? Or do they think some of the UNIX functions are unnecessary? Is Windows a tweak from UNIX? Or, is there any great OS features that were invented in MS to make Windows better than UNIX?

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  • SQL SERVER – Fix: Error: 147 An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference

    - by pinaldave
    Everybody was beginner once and I always like to get involved in the questions from beginners. There is a big difference between the question from beginner and question from advanced user. I have noticed that if an advanced user gets an error, they usually need just a small hint to resolve the problem. However, when a beginner gets error he sometimes sits on the error for a long time as he/she has no idea about how to solve the problem as well have no idea regarding what is the capability of the product. I recently received a very novice level question. When I received the problem I quickly see how the user was stuck. When I replied him with the solution, he wrote a long email explaining how he was not able to solve the problem. He thanked multiple times in the email. This whole thing inspired me to write this quick blog post. I have modified the user’s question to match the code with AdventureWorks as well simplified so it contains the core content which I wanted to discuss. Problem Statement: Find all the details of SalesOrderHeaders for the latest ShipDate. He comes up with following T-SQL Query: SELECT * FROM [Sales].[SalesOrderHeader] WHERE ShipDate = MAX(ShipDate) GO When he executed above script it gave him following error: Msg 147, Level 15, State 1, Line 3 An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference. He was not able to resolve this problem, even though the solution was given in the query description itself. Due to lack of experience he came up with another version of above query based on the error message. SELECT * FROM [Sales].[SalesOrderHeader] HAVING ShipDate = MAX(ShipDate) GO When he ran above query it produced another error. Msg 8121, Level 16, State 1, Line 3 Column ‘Sales.SalesOrderHeader.ShipDate’ is invalid in the HAVING clause because it is not contained in either an aggregate function or the GROUP BY clause. What he wanted actually was the SalesOrderHeader all the Sales shipped on the last day. Based on the problem statement what the right solution is as following, which does not generate error. SELECT * FROM [Sales].[SalesOrderHeader] WHERE ShipDate = (SELECT MAX(ShipDate) FROM [Sales].[SalesOrderHeader]) Well, that’s it! Very simple. With SQL Server there are always multiple solution to a single problem. Is there any other solution available to the problem stated? Please share in the comment. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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