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  • What's the boost way to create a functor that binds out an argument

    - by Mordachai
    I have need for a function pointer that takes two arguments and returns a string. I would like to pass an adapter that wraps a function that takes one argument, and returns the string (i.e. discard one of the arguments). I can trivially build my own adapter, that takes the 2 arguments, calls the wrapped function passing just the one argument through. But I'd much rather have a simple way to create an adapter on the fly, if there is an easy way to do so in C++/boost? Here's some details to make this a bit more concrete: typedef boost::function<CString (int,int)> TooltipTextFn; class MyCtrl { public: MyCtrl(TooltipTextFn callback = boost::bind(&MyCtrl::GetCellText, this, _1, _2)) : m_callback(callback) { } // QUESTION: how to trivially wrapper GetRowText to conform to TooltipTextFn by just discarding _2 ?! void UseRowText() { m_callback = boost::bind(&MyCtrl::GetRowText, this, _1, ??); } private: CString GetCellText(int row, int column); CString GetRowText(int row); TooltipTextFn m_callback; } Obviously, I can supply a member that adapts GetRowText to take two arguments and only passes the first to GetRowText() itself. But is there already a boost binder / adapter that lets me do that?

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  • With this generics code why am I getting "Argument 1: cannot convert from 'ToplogyLibrary.Relationsh

    - by Greg
    Hi, Any see why I'm getting a "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase' to 'TRelationship'" in the code below, in CreateRelationship() ? public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, TNode> Nodes { get; private set; } public List<TRelationship> Relationships { get; private set; } // Constructors protected TopologyBase() { Nodes = new Dictionary<TKey, TNode>(); Relationships = new List<TRelationship>(); } // Methods public TNode CreateNode(TKey key) { var node = new TNode {Key = key}; Nodes.Add(node.Key, node); return node; } public void CreateRelationship(TNode parent, TNode child) { // Validation if (!Nodes.ContainsKey(parent.Key) || !Nodes.ContainsKey(child.Key)) { throw new ApplicationException("Can not create relationship as either parent or child was not in the graph: Parent:" + parent.Key + ", Child:" + child.Key); } // Add Relationship var r = new RelationshipBase<TNode>(); r.Parent = parent; r.Child = child; Relationships.Add(r); // *** HERE *** "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase<TNode>' to 'TRelationship'" } } public class RelationshipBase<TNode> { public TNode Parent { get; set; } public TNode Child { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } }

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  • derived class as default argument g++

    - by Vincent
    Please take a look at this code: template<class T> class A { class base { }; class derived : public A<T>::base { }; public: int f(typename A<T>::base& arg = typename A<T>::derived()) { return 0; } }; int main() { A<int> a; a.f(); return 0; } Compiling generates the following error message in g++: test.cpp: In function 'int main()': test.cpp:25: error: default argument for parameter of type 'A<int>::base&' has type 'A<int>::derived' The basic idea (using derived class as default value for base-reference-type argument) works in visual studio, but not in g++. I have to publish my code to the university server where they compile it with gcc. What can I do? Is there something I am missing?

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  • Why do I get "mysql_query(): supplied argument is not a valid"

    - by Brian Ojeda
    Why do I get a "mysql_query(): supplied argument is not a valid" for the first... $r = mysql_query($q, $connection); In the following code... $bId = trim($_POST['bId']); $title = trim($_POST['title']); $story = trim($_POST['story']); $q = "SELECT * "; $q .= "FROM " . DB_NAME . ".`blog` "; $q .= "WHERE `blog`.`id` = {$bId}"; $r = mysql_query($q, $connection); //confirm_query($r); if (mysql_num_rows($r) == 1) { $q = "UPDATE " . DB_NAME . ".`blog` SET `title` = '{$title}', `story` = '{$story}' WHERE `id` = {$bId}"; $r = mysql_query($q, $connection); if (mysql_affected_rows() == 1) { //Successful $data['success'] = true; $date['errors'] = false; $date['message'] = "You are the Greatest!"; } else { //Fail $data['success'] = false; $data['error'] = true; $date['message'] = "You can't do it fool!"; } } I also get an "mysql_num_rows(): supplied argument is not a valid MySQL result resource" error too. Side notes: I am using 1&1 Hosting (worst hosting ever), custom .htaccess file with one line text to enable PHP 5.2 (only why with 1&1 Hosting).

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  • Argument type deduction, references and rvalues

    - by uj2
    Consider the situation where a function template needs to forward an argument while keeping it's lvalue-ness in case it's a non-const lvalue, but is itself agnostic to what the argument actually is, as in: template <typename T> void target(T&) { cout << "non-const lvalue"; } template <typename T> void target(const T&) { cout << "const lvalue or rvalue"; } template <typename T> void forward(T& x) { target(x); } When x is an rvalue, instead of T being deduced to a constant type, it gives an error: int x = 0; const int y = 0; forward(x); // T = int forward(y); // T = const int forward(0); // Hopefully, T = const int, but actually an error forward<const int>(0); // Works, T = const int It seems that for forward to handle rvalues (without calling for explicit template arguments) there needs to be an forward(const T&) overload, even though it's body would be an exact duplicate. Is there any way to avoid this duplication?

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  • Invalid Argument javascript error only on certain computers

    - by Jen
    Getting an error whenever we click a particular button/link on our site. It is generating a javascript "Invalid Argument" error. I know in the other posts it is typically because it is a syntax error in the javascript however it only just seems to have started happening and it doesn't happen on all pcs. ie. in our client's environment if I remote onto their web server and view the uat website I get the javascript error. If I remote onto their sql server and view the uat website I don't get the javascript error. If it was a syntax error then I would always get the error wouldn't I? both browsers are the same version of IE6 (yeah I know...) :) I have tried deleting temporary internet files - including viewing the files and deleting them myself - but no joy. client uses citrix.. and they're all getting the error :( Any ideas would be appreciated - Thanks! :) Update - Sorry I haven't posted specific code as there is too much to post (and I'm not sure where the error is occurring). The "button" launches a new window which in turn opens up a couple of aspx pages and calls lots of javascript. So the window opens ok, and there's a function that gets called to resize the window - but before it calls the resizing of the window/content it throws the invalid argument error. Am busy trying to get alerts to trigger to see if I can see where it's falling over but so far no luck. Again not sure why this error doesn't occur when I use a particular PC (same browser version)

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  • Angular throws "Error: Invalid argument." in IE

    - by przno
    I have a directive which takes element's text and places wbr elements after every 10th character. I'm using it for example on table cells with long text (e.g. URLs), so it does not span over the table. Code of the directive: myApp.directive('myWbr', function ($interpolate) { return { restrict: 'A', link: function (scope, element, attrs) { // get the interpolated text of HTML element var expression = $interpolate(element.text()); // get new text, which has <wbr> element on every 10th position var addWbr = function (inputText) { var newText = ''; for (var i = 0; i < inputText.length; i++) { if ((i !== 0) && (i % 10 === 0)) newText += '<wbr>'; // no end tag newText += inputText[i]; } return newText; }; scope.$watch(function (scope) { // replace element's content with the new one, which contains <wbr>s element.html(addWbr(expression(scope))); }); } }; }); Works fine except in IE (I have tried IE8 and IE9), where it throws an error to the console: Error: Invalid argument. Here is jsFiddle, when clicking on the button you can see the error in console. So obvious question: why is the error there, what is the source of it, and why only in IE? (Bonus question: how can I make IE dev tools to tell me more about error, like the line from source code, because it took me some time to locate it, Error: Invalid argument. does not tell much about the origin.) P.S.: I know IE does not know the wbr at all, but that is not the issue. Edit: in my real application I have re-written the directive to not to look on element's text and modify that, but rather pass the input text via attribute, and works fine now in all browsers. But I'm still curious why the original solution was giving that error in IE, thus starting the bounty.

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  • SQL Like keyword in Dynamic Linq

    - by Erwin
    Hi fellow programmer I want to use SQL's Like keyword in dynamic LINQ. The query that I want to make is like this select * from table_a where column_a like '%search%' Where the column_a can be dynamically changed to other column etc In this dynamic LINQ var result = db.table_a.Where( a=> (a.column_a.Contains("search")) ); But the column can't be dynamically changed , only the search key can How do we create a dynamic LINQ like var result = db.table_a.Where("column_a == \"search\""); That we can change the column and the search key dynamically

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  • implementing a state machine using the "yield" keyword

    - by Matt Warren
    Is it feasible to use the yield keyword to implement a simple state machine as shown here. To me it looks like the C# compiler has done the hard work for you as it internally implements a state machine to make the yield statement work. Can you piggy-back on top of the work the compiler is already doing and get it to implement most of the state machine for you? Has anyone done this, is it technically possible?

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  • isnt as a c# keyword

    - by Mikael
    To check if an object is of a certain class one can write: if (item is Class) why isn't the opposite possible? if (item isnt Class) instead one would write if (!(item is Class) which isn't as easy to read as if "isnt" was a keyword just as "is" is. Is there something that makes it so that only "is" should be available or has "isnt" just been forgotten about?

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  • Difference in output from use of synchronized keyword and join()

    - by user2964080
    I have 2 classes, public class Account { private int balance = 50; public int getBalance() { return balance; } public void withdraw(int amt){ this.balance -= amt; } } and public class DangerousAccount implements Runnable{ private Account acct = new Account(); public static void main(String[] args) throws InterruptedException{ DangerousAccount target = new DangerousAccount(); Thread t1 = new Thread(target); Thread t2 = new Thread(target); t1.setName("Ravi"); t2.setName("Prakash"); t1.start(); /* #1 t1.join(); */ t2.start(); } public void run(){ for(int i=0; i<5; i++){ makeWithdrawl(10); if(acct.getBalance() < 0) System.out.println("Account Overdrawn"); } } public void makeWithdrawl(int amt){ if(acct.getBalance() >= amt){ System.out.println(Thread.currentThread().getName() + " is going to withdraw"); try{ Thread.sleep(500); }catch(InterruptedException e){ e.printStackTrace(); } acct.withdraw(amt); System.out.println(Thread.currentThread().getName() + " has finished the withdrawl"); }else{ System.out.println("Not Enough Money For " + Thread.currentThread().getName() + " to withdraw"); } } } I tried adding synchronized keyword in makeWithdrawl method public synchronized void makeWithdrawl(int amt){ and I keep getting this output as many times I try Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw This shows that only Thread t1 is working... If I un-comment the the line saying t1.join(); I get the same output. So how does synchronized differ from join() ? If I don't use synchronize keyword or join() I get various outputs like Ravi is going to withdraw Prakash is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Prakash is going to withdraw Ravi is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Prakash is going to withdraw Ravi is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Account Overdrawn Account Overdrawn Not Enough Money For Ravi to withdraw Account Overdrawn Not Enough Money For Prakash to withdraw Account Overdrawn Not Enough Money For Ravi to withdraw Account Overdrawn Not Enough Money For Prakash to withdraw Account Overdrawn So how does the output from synchronized differ from join() ?

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  • Oracle "Partition By" Keyword

    - by Nalandial
    Can someone please explain what the "partition by" keyword does and give a simple example of it in action, as well as why one would want to use it? I have a SQL query written by someone else and I'm trying to figure out what it does. An example of partition by: SELECT empno, deptno, COUNT(*) OVER (PARTITION BY deptno) DEPT_COUNT FROM emp The examples I've seen online seem a bit too in-depth. Thanks in advance!

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  • Keyword Selection Background?

    - by Irwin
    I just installed MSVS2010 Ultimate & I've noticed something which is somewhat annoying & conflicting with my syntax highlighting, as can be seen: As can be seen, when a keyword/function/variable/etc is highlighted all other instances of the aforementioned are highlighted too. This is somewhat annoying. Is there any way to disable this?

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  • VB.NET Use With keyword on existing object?

    - by ropstah
    Is it somehow possible to use the 'With' keyword on an existing object? I would like to do the following using LINQ to objects and can't seem to find a way: From m as Product in Me _ Select m With {.Match = m.Name.IndexOf(query)} _ Where m.Name.IndexOf(query) > 0

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  • ruby keyword arguments of method

    - by Yang
    How can I declare a method with keyword arguments just like rails do. some examples may be Person.find(:all, :conditions => "..."). How can I use symbols to create methods similar to the above? I am very new to ruby. Thanks in advance!

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