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  • Assigning a pointer variable to a const int in C++?

    - by John
    I'm wondering if anyone can explain the following to me: If I write int i = 0; float* pf = i; I get a compile error (gcc 4.2.1): error: invalid conversion from ‘int’ to ‘float*’ Makes sense - they are obviously two completely different types. But if instead I write const int i = 0; float* pf = i; It compiles without error. Why should the 'const' make a difference on the right hand side of the assignment? Isn't part of the idea of the 'const' keyword to be able to enforce type constraints for constant values? Any explanation I have been able to come up with feels kind of bogus. And none of my explanations also explain the fact that const int i = 1; float* pf = i; fails to compile. Can anyone offer an explanation?

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  • prevent onmouseout when hovering child element of the parent absolute div

    - by John
    Hi I am having trouble with the onmouseout function in a absolute positoned div. When the mouse hits a child element in the div, the mouseout event fires, but I do not want it to fire until the mouse is out of the parent, absolute div. How can I prevent the mouseout event from firing when it hits a child element WITHOUT jquery. I know this has something to do with event bubbling, but I am having no luck on finding out how to work this out. A similar post I found here: How to disable mouseout events triggered by child elements? How ever that solution uses jquery.

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  • Small questions on data structure

    - by John Graveston
    Hi, I'm trying to search the parent of a node with Kruskal's algorithm. My program works just fine, but I think I have heard of a method to improve the speed of the algorithm by reconstructing the tree while searching for the parent node and connecting it to the parent node. I'm pretty sure that I've heard of this somewhere, maybe in a lecture. Can anyone refresh my memory? And also, given a number of arrays, when searching for the minimum and the maximum value from a certain section of an array, what is the name of the tree that can calculate the minimum/maximum value from the array by making a binary tree that has the minimum/maximum value of each array in O(log N)?

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  • C++: use array of strings wrapped in namespace?

    - by John D.
    I got the following code, wishing to wrap a group of strings nicely in a namespace: namespace msgs { const int arr_sz = 3; const char *msg[arr_sz] = {"blank", "blank", "blank" }; msg[0] = "Welcome, lets start by getting a little info from you!\n"; msg[1] = "Alright, bla bla bla.."; msg[2] = "etc."; } The code inside works nicely inside a function, but I don't know how to return an array from it. The namespace idea LOOKS fine, but it returns on the last three lines: error: expected constructor, destructor, or type conversion before ‘=’ token Why can't I define the array inside a namespace, do I need to do something first? It's nice because I can call it like printf(msgs::msg[1]) etc. I want to do this I just can't wrap my head around what's wrong :(

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  • boost::function & boost::lambda - call site invocation & accessing _1 and _2 as the type

    - by John Dibling
    Sorry for the confusing title. Let me explain via code: #include <string> #include <boost\function.hpp> #include <boost\lambda\lambda.hpp> #include <iostream> int main() { using namespace boost::lambda; boost::function<std::string(std::string, std::string)> f = _1.append(_2); std::string s = f("Hello", "There"); std::cout << s; return 0; } I'm trying to use function to create a function that uses the labda expressions to create a new return value, and invoke that function at the call site, s = f("Hello", "There"); When I compile this, I get: 1>------ Build started: Project: hacks, Configuration: Debug x64 ------ 1>Compiling... 1>main.cpp 1>.\main.cpp(11) : error C2039: 'append' : is not a member of 'boost::lambda::lambda_functor<T>' 1> with 1> [ 1> T=boost::lambda::placeholder<1> 1> ] Using MSVC 9. My fundamental understanding of function and lambdas may be lacking. The tutorials and docs did not help so far this morning. How do I do what I'm trying to do?

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  • Load php file wth xml header

    - by John Smith
    I have a php file with an xml header and xml code, named test.php. How do I load this file as an xml? The following doesn't work: $xml = simplexml_load_file('test.php'); echo $xml; I just get a white page. The test file is saved as php, as it's dynamic. It's loading data from the tradedoubler api. The xml looks something like this: <voucherList> <voucher> <id>115</id> <programId>111</programId> <programName>Program 111</programName> <code>AF30C5</code> <updateDate>1332422674941</updateDate> <startDate>1332370800000</startDate> <endDate>1363906800000</endDate> <title>Voucher number one</title> <shortDescription>Short description of the voucher.</shortDescription> <description>This is a long version of the voucher description.</description> <voucherTypeId>1</voucherTypeId> <defaultTrackUri>http://clk.tradedoubler.com/click?a(222)p(111)ttid(13)</defaultTrackUri> <siteSpecific>True</siteSpecific> </voucher> <voucher> <id>116</id> <programId>111</programId> <programName>Program 111</programName> <code>F90Z4F</code> <updateDate>1332423212631</updateDate> <startDate>1332370800000</startDate> <endDate>1363906800000</endDate> <title>The second voucher</title> <shortDescription>Short description of the voucher.</shortDescription> <description>This is a long version of the voucher description.</description> <voucherTypeId>1</voucherTypeId> <defaultTrackUri>http://clk.tradedoubler.com/click?a(222)p(111)ttid(13)url(http://www.example.com/product?id=123)</defaultTrackUri> <siteSpecific>False</siteSpecific> <landingUrl>http://www.example.com/product?id=123</landingUrl> </voucher> </voucherList>

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  • How to stop a MFC/win32 control re-painting

    - by John
    I have a CRichEditCtrl, and an algorithm works on its contents in-place, iterating through the contents and making changes. This seems to cause it to re-paaint every time, which causes flickering and a noticeable time to complete the operation, especially if the control starts scrolling. I wondered if there's a neat way for me to stop it repainting for a period. It's actually a custom subclass of CRichEditCtrl in use so I was thinking something like: void MyCustomEditCtrl::DoAlgorithm() { enableRepaint(false); ... //to the actual work ... enableRepaint(true); } What's the neatest approach? A custom on-paint handler which does nothing when an operation is in progress? Or can repainting actually be disabled?

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  • Creating a C# DLL and using it from unmanaged C++

    - by John
    I have a native (unmanaged) C++ application (using wxWidgets for what it's worth). I'm considering a separate tool application to be written in C# which would contain winform-based dialogs. putting some of those dialogs in a separate DLL would be useful as I'd hope to be able to use them from my C++ app. But I have no idea how much messing about is needed to accomplish this, is it particularly easy?

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  • c++: what is a good idea for a list of strings?

    - by John
    I simply want to build an RPG and make it as neat as possible, I wish to define a pile of strings which I may want to edit later, so I tried something like this: enum {MSG_INIT = "Welcome to ...", MSG_FOO = "bar"}; But I just get errors, such as that MSG_INIT is not an integer! Why must it not be a string, are that what enums are only for? What do you think is the best way to define a pile of strings? In a struct called msg or something? I'm kinda new to all this so I'd really appreciate small examples.

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  • Hide table row onclick using jquery

    - by John
    I have a bunch of table rows such as: <tr> <td>cell1</td> <td>cell2</td> <td><a href="action.php">cell3</a></td> </tr> <tr class="notes_row"> <td colspan="6"> <ul class="message warning no-margin" id="notes_box"> <li>Notes here</li> </ul> </td> </tr> <tr> <td>cell1</td> <td>cell2</td> <td><a href="action.php">cell3</a></td> </tr> The class="notes_row" is only there if notes are present for the row above it. How can I hide the tr and if its there the tr with the notes_row class below it without affecting the other rows using jquery? So if someone clicked cell3 the tr that link is in is hidden then if there is a notes table row below it, it hides that as well.

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  • Maintaining many socket connections with a single thread

    - by John
    Many tutorials on socket communication I see seem to use 1 thread per socket. But on a server used for online gaming, you might have 10k concurrent users - 10k threads isn't probably a wonderful idea. I came across a tool (SmartFox) which claims to use a single thread for monitoring all socket connections, potentially thousands of them. This app happens to be in Java, but I figure C++ or C# could do the same... how would you achieve this?

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  • Visual Studio 2008 - Is it possible for two projects to share common classes?

    - by John M
    In Visual Studio 2008 I know its possible to have one solution with two (or more) projects. Is it possible OR How is it possible for the projects to share common class files? For example - Project 1 has a log file handling class. Can Project 2 reference it? My hope is to increase code re-use and avoid two copies of the same thing that need to be maintained. The target is Winforms C# (3.5)

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  • How to test that invalid arguments raise an ArgumentError exception using RSpec?

    - by John Topley
    I'm writing a RubyGem that can raise an ArgumentError if the arguments supplied to its single method are invalid. How can I write a test for this using RSpec? The example below shows the sort of implementation I have in mind. The bar method expects a single boolean argument (:baz), the type of which is checked to make sure that it actually is a boolean: module Foo def self.bar(options = {}) baz = options.fetch(:baz, true) validate_arguments(baz) end def self.validate_arguments(baz) raise(ArgumentError, ":baz must be a boolean") unless valid_baz?(baz) end def self.valid_baz?(baz) baz.is_a?(TrueClass) || baz.is_a?(FalseClass) end end

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  • Should multiple regional websites all use the same database?

    - by John Himmelman
    I'm developing a cms for a company that has multiple regional sites (us, uk, china, russia, etc..). Should I use a separate database for each of these sites or use a single database with a 'site' field in each table? My main concern is the table language encoding (ie, can storing strings in different langauges in the same table cause problems, such as sorting issues).

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  • Storing information in the DOM?

    - by John
    Im making a small private message application in the form of a phone. Ten messages are shown at the time. And the list of messages are scrolled up/down by hiding them. Just how bad is it to use the DOM to store information in this way. My main goal for doing this is to reduce calls to the database. And instead of making a new call all the time, it only checks if any new messages has arrived and ads the new message(s). Whats the alternative, cookies anyone? Thank you for the time

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  • Using LINQ, how do you get all label controls.

    - by John
    I want to get a collection of all label controls that are part of a user control. I have the following code: var labelControls = from Control ctl in this.Controls where ctl.GetType() == typeof(Label) select ctl; but the result is zero results. Please assist. Thanks.

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  • What do I need to know before working on an IM application?

    - by John
    I'm looking into building an IM-type application using Java stack (for the server at least). I'd be interested to see any information/advice on how applications like Skype/AIM/MSN work, as well as know any technologies/APIs that might be relevant. Without giving away the idea itself, it's perhaps more akin to Google Wave than Skype, but information useful for either is very welcome. Specific points I have already thought of include: Server Vs P2P... for reasons of logging my system will require all communication to go through a central server. Is this how other IM tools work... especially when audio/video comes into the equation? Cross-communication with other systems. Are there APIs for this or do all IM providers work hard to keep their protocol secret? The nature of what I'm designing means integration could probably only be limited, but it definitely seems worthwhile from a business perspective

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  • Extending struts 2 "property" data tag

    - by John B.
    Hi, We are currently developing a project with Struts2. We have a module on which we display a large amount of data on read-only fields from a group of beans via the "property" Struts 2 data tag (i.e. <s:property value="aBeanProperty" /) on a jsp file. In some cases most of the fields might come empty, so a blank is being displayed on screen. Our customer is now requesting us to display default string (i.e. "N/A") whenever a property comes empty, so that it is displayed in place of the blank spaces currently shown. We are looking for a way to achieve this in a clean and maintainable way. The 'property' tag comes with a 'default' attribute on which one can define a default value in cases when the accessed property comes as null. However, most of our properties are empty strings, therefore it does not work in our case. Another solution we are thinking of is to define a base class for all of our beans, and define a util method which will validate if a string is null or empty and then return the default value. Then we would call this method from each bean getter. And yes this would be tiresome and kind of ugly :), therefore we are holding out on this one in case of a better solution. Now, we have in mind a solution which we think would be the best but have not had luck on how implement it. We are planning on extending the 'property' tag some way, defining a new 'default' attribute so that besides working on null properties, it also do so on empty strings ("", " ", etc). Therefore we would only need to replace the original s:property tag with our new custom tag, and the desired result would be achieved without touching java code. Do you have an idea on how to do this? Also, any other clever solution (maybe some sort of design pattern?) on how to default the values of a large amount of property beans are welcome too! (Or maybe, even there might be some tag that does this already in Struts2??) Thanks in advance.

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  • sports league database design

    - by John
    Hello, I'm developing a database to store statistics for a sports league. I'd like to show several tables: - league table that indicates the position of the team in the current and previous fixture - table that shows the position of a team in every fixture in the championship I have a matches table: Matches (IdMatch, IdTeam1, IdTeam2, GoalsTeam1, GoalsTeam2) Whith this table I can calculate the total points of every team based on the matches the team played. But every time I want to show the league table I have to calculate the points. Also I have a problem to calculate in which position classified a team in the last 10 fixtures cause I have to make 10 queries. To store the league table for every fixture in a database table is another approach, but every time I change a match already played I have to recalculate every fixture from there... Is there a better approach for this problem? Thanks

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  • Check and avoid if a char is being entered in a int

    - by John
    Hi.... This is a exremely stupid question but i need help with this.... I'm trying to make a small program that i made robust and needed some help with tht.... int num1; int num2 = 0; System.out.print("Enter number 1: "); num1 = kb.nextInt(); while(num2<num1) { System.out.print("Enter number 2: "); num2 = kb.nextInt(); } Number 2 has to be greater than number 1 Also i want the program to automatically check and ignore if the user enters a char instead of an int... Cause right now when a user enters lets say "r" instead of a number the program just exists....

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