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  • interface variables are final and static by default and methods are public and abstract

    - by sap
    The question is why it's been decided to have variable as final and static and methods as public and abstract by default. Is there any particular reason for making them implicit,variable as final and static and methods as public and abstract. Why they are not allowing static method but allowing static variable? We have interface to have feature of multiple inheritance in Java and to avoid diamond problem. But how it solves diamond problem,since it does not allow static methods. In the following program, both interfaces have method with the same name..but while implementing only one we implement...is this how diamond problem is solved? interface testInt{ int m = 0; void testMethod(); } interface testInt1{ int m = 10; void testMethod(); } public class interfaceCheck implements testInt, testInt1{ public void testMethod(){ System . out . println ( "m is"+ testInt.m ); System . out . println ( "Hi World!" ); } }

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  • How to handle window closed in the middle of a long running operation gracefully?

    - by Marek
    We have the following method called directly from the UI thread: void DoLengthyProcessing() { DoStuff(); var items = DoMoreStuff(); //do even more stuff - 200 lines of code trimmed this.someControl.PrepareForBigThing(); //someControl is a big user control //additional 100 lines of code that access this.someControl this.someControl.Finish(items); } Many of the called methods call Application.DoEvents() (and they do so many times) (do not ask me why, this is black magic written by black magic programmers and it can not be changed because everyone is scared what the impact would be) and there is also an operation running on a background thread involved in the processing. As a result, the window is not fully nonresponsive and can be closed manually during the processing. The Dispose method of the form "releases" the someControl variable by setting it to null. As a result, in case the user closes the window during the lengthy process, a null reference exception is thrown. How to handle this gracefully without just catching and logging the exception caused by disposal? Assigning the someControl instance to a temporary variable in the beginning of the method - but the control contains many subcontrols with similar disposal scheme - sets them to null and this causes null reference exceptions in other place put if (this.IsDisposed) return; calls before every access of the someControl variable. - making the already nasty long method even longer and unreadable. in Closing event, just indicate that we should close and only hide the window. Dispose it at the end of the lengthy operation. This is not very viable because there are many other methods involved (think 20K LOC for a single control) that would need to handle this mechanism as well. How to most effectively handle window disposal (by user action) in the middle of this kind of processing?

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  • Friends, templates, overloading <<

    - by Crystal
    I'm trying to use friend functions to overload << and templates to get familiar with templates. I do not know what these compile errors are: Point.cpp:11: error: shadows template parm 'class T' Point.cpp:12: error: declaration of 'const Point<T>& T' for this file #include "Point.h" template <class T> Point<T>::Point() : xCoordinate(0), yCoordinate(0) {} template <class T> Point<T>::Point(T xCoordinate, T yCoordinate) : xCoordinate(xCoordinate), yCoordinate(yCoordinate) {} template <class T> std::ostream &operator<<(std::ostream &out, const Point<T> &T) { std::cout << "(" << T.xCoordinate << ", " << T.yCoordinate << ")"; return out; } My header looks like: #ifndef POINT_H #define POINT_H #include <iostream> template <class T> class Point { public: Point(); Point(T xCoordinate, T yCoordinate); friend std::ostream &operator<<(std::ostream &out, const Point<T> &T); private: T xCoordinate; T yCoordinate; }; #endif My header also gives the warning: Point.h:12: warning: friend declaration 'std::ostream& operator<<(std::ostream&, const Point<T>&)' declares a non-template function Which I was also unsure why. Any thoughts? Thanks.

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  • JavaScript: How is "function x() {}" different from "x = function() {}" ?

    - by jleedev
    In the answers to this question, we read that function f() {} defines the name locally, while [var] f = function() {} defines it globally. That makes perfect sense to me, but there's some strange behavior that's different between the two declarations. I made an HTML page with the script onload = function() { alert("hello"); } and it worked as expected. When I changed it to function onload() { alert("hello"); } nothing happened. (Firefox still fired the event, but WebKit, Opera, and Internet Explorer didn't, although frankly I've no idea which is correct.) In both cases (in all browsers), I could verify that both window.onload and onload were set to the function. In both cases, the global object this is set to the window, and I no matter how I write the declaration, the window object is receiving the property just fine. What's going on here? Why does one declaration work differently from the other? Is this a quirk of the JavaScript language, the DOM, or the interaction between the two?

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  • google maps api keys to be set webserver-wide, (as env var? inside apache?)

    - by ~knb
    I have a web site with many virtual hosts and each registered with several domain names (ending in .org, .de), site1.mysite.de, site2.mysite.org Then I have different templating systems based on several programming languages (perl and php) in use on the web server. The Google Maps Api requires a unique Google Maps api key for each vhost. I want to have something like a web-server wide variable $goomapkey that I can call from inside my code. In PHP code, Now I have a kludgy case-analysis solution like $domain = substr($_SERVER['SERVER_NAME'], -3); if (".de" == $domain){ //if ("xxxxxx" eq substr($ENV{SERVER_NAME}, 0, 5)){ // $gookey = "ABQIAAA..."; //} else { //site1.de $gookey = "ABQIAAAA1Js..."; //} } elseif ("dev" == substr($_SERVER['SERVER_NAME'], 0, 3)){ //dev.mysite.org $gookey = "ABQIAAAA1JsSb..."; } else { //www.mysite.org $gookey = "ABQIAAAA1JsS..."; //TODO: Add more keys for each virtual host, for my.machinename.de, IP-address based URL, ... } ... inside my php-based CMS. A non-ideal solution, because it is, php-only, and I still have to set it at several html templates inside the CMS, and there are too many cases. I want the google maps api key to be set by the apache web server who examines the request *early in the request loop before any php page template code is constructed and evaluated. is an environment variable a good solution? which technology should be used to set the $goomapkey variable? I'd prefer mod_perl2 Apache request handler, but the documentation is confusing (many API changes in the past ). Which Apache module could I use? Is there a built-in Apache module that does the same thing?

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  • C# and Objects/Classes

    - by user1192890
    I have tried to compile code from Deitel's C# 2010 for programmers. I copied it exactly out of the book, but it still can't find main, even though I declared it in one of the classes. Here is a look at the two classes: For GradeBookTest: // Fig. 4.2: GradeBookTest.cs // Create a GradeBook object and call its DisplayMessage method. public class GradeBookTest { // Main method begins program execution public static void Main(string[] args) { // create a GradeBook object and assign it to myGradeBook GradeBook myGradeBook = new GradeBook(); // call myGradeBook's DisplayMessage method myGradeBook.DisplayMessage(); } // end Main } // end class GradeBookTest Now for the GradeBook class: // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook That is how I copied them. Here is how they appeared in the book: 1 // Fig. 4.2: GradeBookTest.cs 2 // Create a GradeBook object and call its DisplayMessage method. 3 public class GradeBookTest 4 { 5 // Main method begins program execution 6 public static void Main( string[] args ) 7 { 8 // create a GradeBook object and assign it to myGradeBook 9 GradeBook myGradeBook = new GradeBook(); 10 11 // call myGradeBook's DisplayMessage method 12 myGradeBook.DisplayMessage(); 13 } // end Main 14 } // end class GradeBookTest and // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook I don't see why they are not working. Right now I am using Visual Studio Pro 2010. Any Thoughts?

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  • Stopping a MATLAB GUI callback

    - by leonhart88
    Dear All, I have a START and STOP button. When I hit START, i run a bunch of code in my callback. It's basically a sequential "script" that opens valves, dispenses water and then closes the valves...there is no while() loop and it doesn't repeat. I want to be able to stop this process at any time using the STOP button. Most of the related answers I've seen are in the cases where a while() loop is used. Some people have also suggested to periodically check if the STOP button was pressed (using a variable or handle variable). Since I do not have a while loop, I can't solve it that way. Also, I'd like to be able to exit immediately, without having to periodically check (because checking multiple times in my code would be ugly and confusing). Is there a way to terminate the callback which was interrupted by the STOP button? If not, is it possible to have the START button run a .m file and then have the STOP button terminate that .m file? The worst case scenario would be to check a variable periodically. UPDATE: Well, looks like the worst case scenario is what is suggested by MATLAB... http://www.mathworks.com/support/solutions/en/data/1-33IK85/index.html?product=ML&solution=1-33IK85 Thanks.

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  • 2 dimensional arrays passed to a function in c++

    - by John Marcus
    I'm working on doing calculations in a two dimensional array but keep getting a nasty error. i call the function by : if(checkArray(array)) and try to pass it in like this: bool checkArray(double array[][10]) //or double *array[][10] to no avail the error is error: cannot convert ‘double ()[(((unsigned int)(((int)n) + -0x00000000000000001)) + 1)]’ to ‘double’ for argument ‘1’ to ‘bool checkArray(double*)’ code snippet //array declaration int n = 10; double array[n][n]; //function call to pass in array while(f != 25) { cout<<endl; cout<<endl; if(checkArray(array)) //this is the line of the error { cout<<"EXIT EXIT EXIT"<<endl; } f++; } //function declaration bool checkArray(double *array)//, double newArray[][10]) { double length = sizeof(array); for(int i = 0; i < length; i++) for(int j = 0; j < length;j++) { double temp = array[i][j]; } }

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  • How do I change or add data to a data repeater and get it to display in ASP.NET

    - by CowKingDeluxe
    Here is my code-behind, this adds the "OakTreeName" to the datarepeater. There's about 200 of them. Dim cmd As New SqlClient.SqlCommand("OakTree_Load", New SqlClient.SqlConnection(ConnStr)) cmd.CommandType = CommandType.StoredProcedure cmd.Connection.Open() Dim datareader As SqlClient.SqlDataReader = cmd.ExecuteReader() OakTree_Thumb_Repeater.DataSource = datareader OakTree_Thumb_Repeater.DataBind() cmd.Connection.Close() Here is essentially what I'd like to do with my markup: <ContentTemplate> <asp:Repeater ID="OakTree_Thumb_Repeater" runat="server"> <ItemTemplate> <asp:ImageButton ImageUrl="<%# Container.DataItem("OakTreeName") %>" AlternateText="" runat="server" /> <!-- Or I'd like to do it this way by adding a custom variable to the data repeater --> <asp:ImageButton ImageUrl="<%# Container.DataItem("OakTreeThumbURL") %>" AlternateText="" runat="server" /> </ItemTemplate> </asp:Repeater> </ContentTemplate> I would like to manipulate the "OakTreeName" variable before it gets placed into the item template. Basically I need to manipulate the "OakTreeName" variable and then input it as the ImageURL for the imagebutton within the item template. How do I do this? Am I approaching this wrong? Is there a way to manipulate the item template from code-behind before it gets displayed for each round of variables in the data repeater?

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  • Splitting Code into Headers/Source files

    - by cam
    I took the following code from the examples page on Asio class tcp_connection : public boost::enable_shared_from_this<tcp_connection> { public: typedef boost::shared_ptr<tcp_connection> pointer; static pointer create(boost::asio::io_service& io_service) { return pointer(new tcp_connection(io_service)); } tcp::socket& socket() { return socket_; } void start() { message_ = make_daytime_string(); boost::asio::async_write(socket_, boost::asio::buffer(message_), boost::bind(&tcp_connection::handle_write, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } private: tcp_connection(boost::asio::io_service& io_service) : socket_(io_service) { } void handle_write(const boost::system::error_code& /*error*/, size_t /*bytes_transferred*/) { } tcp::socket socket_; std::string message_; }; I'm relatively new to C++ (from a C# background), and from what I understand, most people would split this into header and source files (declaration/implementation, respectively). Is there any reason I can't just leave it in the header file if I'm going to use it across many source files? If so, are there any tools that will automatically convert it to declaration/implementation for me? Can someone show me what this would look like split into header/source file for an example (or just part of it, anyway)? I get confused around weird stuff like thistypedef boost::shared_ptr<tcp_connection> pointer; Do I include this in the header or the source? Same with tcp::socket& socket() I've read many tutorials, but this has always been something that has confused me about C++.

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  • Increasing understanding of validating a string with PHP string functions

    - by user1554264
    I've just started attempts to validate data in PHP and I'm trying to understand this concept better. I was expecting the string passed as an argument to the $data parameter for the test_input() function to be formatted by the following PHP functions. trim() to remove white space from the end of the string stripslashes() to return a string with backslashes stripped off htmlspecialchars() to convert special characters to HTML entities The issue is that the string that I am echoing at the end of the function is not being formatted in the way I desire at all. In fact it looks exactly the same when I run this code on my server - no white space removed, the backslash is not stripped and no special characters converted to HTML entities. My question is have I gone about this in the wrong approach? Should I be creating the variable called $santised_input on 3 separate lines with each of the functions trim(), stripslashes() and htmlspecialchars()? By my understanding surely I am overwriting the value of the $santised_input variable each time I recreate it on a new line of code. Therefore the trim() and stripslashes() string functions will never be executed. What I am trying to achieve is using the "$santised_input" variable to run all of these PHP string functions when the $data argument is passed to my test_input() function. In other words can these string functions be chained together so that I only need to create $santised_input once? <?php function test_input($data) { $santised_input = trim($data); $santised_input = stripslashes($data); $santised_input = htmlspecialchars($data); echo $santised_input; } test_input("%22%3E%3Cscript%3Ealert('hacked')%3C/script%3E\ "); //Does not output desired result "&quot;&gt;&lt;script&gt;alert('hacked')&lt;/script&gt;" ?>

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  • position for texture in opengl

    - by Tyzak
    hello, i have a question concerning how to declare the points for a texture on a cube to be exactly i mean the: glTexCoord2f(x.f, y.f); for the front side, my declaration works: glBegin(GL_POLYGON); //Vorderseite glNormal3f(0.0f, 0.0f, 1.0f);//normale für vorderseite glTexCoord2f(0.0f, -1.f); glVertex3f(-fSeitenL/2.0f,-fSeitenL/2.0f,+fSeitenL/2.0f); glTexCoord2f(1.f, -1.f); glVertex3f(+fSeitenL/2.0f,-fSeitenL/2.0f,+fSeitenL/2.0f); glTexCoord2f(1.f, 0.0f); glVertex3f(+fSeitenL/2.0f,+fSeitenL/2.0f,+fSeitenL/2.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-fSeitenL/2.0f,+fSeitenL/2.0f,+fSeitenL/2.0f); glEnd(); but for the right side, it doesn't work, i suggest i need other parameters, for glTexCoord2f, but i don't know witch one. glBegin(GL_POLYGON); //Rechte Seite glNormal3f(1.0f, 0.0f, 0.0f); //normale für rechte seite glTexCoord2f(0.0f, -1.f); glVertex3f(+fSeitenL/2.0f,-fSeitenL/2.0f,+fSeitenL/2.0f); glTexCoord2f(1.0f, -1.f); glVertex3f(+fSeitenL/2.0f,-fSeitenL/2.0f,-fSeitenL/0.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(+fSeitenL/2.0f,+fSeitenL/2.0f,-fSeitenL/0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(+fSeitenL/2.0f,+fSeitenL/2.0f,+fSeitenL/0.0f); glEnd(); after all i close the "texture-declaration with" glDisable(GL_TEXTURE_2D); thanks in advance

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  • PHP PDO Parameters from a function returned array

    - by noko
    I've got a function written that runs a query based on parameters passed to the function. I can't seem to figure out why doing the following returns a result: function test($function_returned_array) { $variable = 'Hello World'; $sql = 'SELECT `name`, `pid` FROM `products` WHERE `name` IN (?)'; $found = $this->db->get_array($sql, $variable); } While this doesn't return any results: function test2($function_returned_array) { $sql = 'SELECT `name`, `pid` FROM `products` WHERE `name` IN (?)'; $found = $this->db->get_array($sql, $function_returned_array[0]); } $function_returned_array[0] is also equal to 'Hello World'. Shouldn't they both return the same results? When I echo the values of $variable and $function_returned_array[0], they are both 'Hello World' Here's the relevant parts of my PDO wrapper: public function query(&$query, $params) { $sth = $this->_db->prepare($query); if(is_null($params)) { $sth->execute(); } else if(is_array($params)) { $sth->execute($params); } else { $sth->execute(array($params)); } $this->_rows = $sth->rowCount(); $this->_counter++; return $sth; } public function get_array(&$query, $params, $style = PDO::FETCH_ASSOC) { $q = $this->query($query, $params); return $q->fetchAll($style); } I'm using PHP 5.3.5. Any help would be appreciated.

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  • Write to PDF using PHP from android device

    - by Brent Mitchell
    I am trying to write to a pdf file on php server. I have sent variables to the server, create the pdf document, then have my phone download the document to view on device. The variables seem not to write on the php file. I have my code below public void postData() { try { Calculate calc = new Calculate(); HttpClient mClient = new DefaultHttpClient(); StringBuilder sb=new StringBuilder("myurl.com/pdf.php"); HttpPost mpost = new HttpPost(sb.toString()); String value = "1234"; List nameValuepairs = new ArrayList(1); nameValuepairs.add(new BasicNameValuePair("id",value)); mpost.setEntity(new UrlEncodedFormEntity(nameValuepairs)); } catch (UnsupportedEncodingException e) { Log.w(" error ", e.toString()); } catch (Exception e) { Log.w(" error ", e.toString()); } } And my php code to write the variable "value" onto the pdf document: //code to reverse the string if($_POST[] != null) { $reversed = strrev($_POST["value"]); $this->SetFont('Arial','u',50); $this->Text(52,68,$reversed); } I am just trying to write the variable in a random spot, but the variable the if statement is always null and I do not know why. Thanks. Sorry if it is a little sloppy.

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  • Cloning ID3DXMesh with declration that has 12 floats breaks?

    - by meds
    I have the following vertex declration: struct MESHVERTInstanced { float x, y, z; // Position float nx, ny, nz; // Normal float tu, tv; // Texcoord float idx; // index of the vertex! float tanx, tany, tanz; // The tangent const static D3DVERTEXELEMENT9 Decl[6]; static IDirect3DVertexDeclaration9* meshvertinstdecl; }; And I declare it as such: const D3DVERTEXELEMENT9 MESHVERTInstanced::Decl[] = { { 0, 0, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0 }, { 0, 12, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_NORMAL, 0 }, { 0, 24, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0 }, { 0, 32, D3DDECLTYPE_FLOAT1, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1 }, { 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 }, D3DDECL_END() }; What I try to do next is copy an ID3DXMesh into another one with the new vertex declaration as such: model->CloneMesh( model->GetOptions(), MESHVERTInstanced::Decl, gd3dDevice, &pTempMesh ); When I try to get the FVF size of pTempMesh (D3DXGetFVFVertexSize(pTempMesh-GetFVF())) I get '0' though the size should be 48. The whole thing is fine if I don't have the last declaration, '{ 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 },' in it and the CloneMesh function does not return a FAIL. I've also tried using different declarations such as D3DDECLUSAGE_TEXCOORD and that has worked fine, returning a size of 48. Is there something specific about D3DDECLUSAGE_TANGENT I don't know? I'm at a complete loss as to why this isn't working...

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  • Call instance method with objc_msgSend

    - by user772349
    I'm trying to use the objc_msgSend method to call some method dynamically. Say I want call some method in Class B from Class A and there are two methods in class B like: - (void) instanceTestWithStr1:(NSString *)str1 str2:(NSString *)str1; + (void) methodTestWithStr1:(NSString *)str1 str2:(NSString *)str1; And I can call the class method like this in Class A successfully: objc_msgSend(objc_getClass("ClassB"), sel_registerName("methodTestWithStr1:str2:"), @"111", @"222"); And I can call the instance method like this in Class A successfully as well: objc_msgSend([[objc_getClass("ClassB") alloc] init], sel_registerName("instanceTestWithStr1:str2:"), @"111", @"222"); But the thing is to get a instance of Class B I have to call "initWithXXXXX:XXXXXX:XXXXXX" instead of "init" so that to pass some necessary parameters to class B to do the init stuff. So I stored a instance of ClassB in class A as variable: self.classBInstance = [[ClassB alloc] initWithXXXXX:XXXXXX:XXXXXX]; And then I call the method like this (successfully): The problem is, I want to call a method by simply applying the classname and the method sel like "ClassName" and "SEL" and then call it dynamically: If it's a class method. then call it like: objc_msgSend(objc_getClass("ClassName"), sel_registerName("SEL")); If it's a instance method, find the existing class instance variable in the calling class then: objc_msgSend([self.classInstance, sel_registerName("SEL")); So I want to know if there is any way to: Check if a class has a given method (I found "responseToSelector" will be the one) Check if a given method in class method or instance method (maybe can use responseToSelector as well) Check if a class has a instance variable of a given class So I can call a instance method like: objc_msgSend(objc_getClassInstance(self, "ClassB"), sel_registerName("SEL"));

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  • Automating Excel through the PIA makes VBA go squiffy.

    - by Jon Artus
    I have absolutely no idea how to start diagnosing this, and just wondered if anyone had any suggestions. I'm generating an Excel spreadsheet by calling some Macros from a C# application, and during the generation process it somehow breaks. I've got a VBA class containing all of my logging/error-handling logic, which I instantiate using a singleton-esque accessor, shown here: Private mcAppFramework As csys_ApplicationFramework Public Function AppFramework() As csys_ApplicationFramework If mcAppFramework Is Nothing Then Set mcAppFramework = New csys_ApplicationFramework Call mcAppFramework.bInitialise End If Set AppFramework = mcAppFramework End Function The above code works fine before I've generated the spreadsheet, but afterwards fails. The problem seems to be the following line; Set mcAppFramework = New csys_ApplicationFramework which I've never seen fail before. If I add a watch to the variable being assigned here, the type shows as csys_ApplicationFramework/wksFoo, where wksFoo is a random worksheet in the same workbook. What seems to be happening is that while the variable is of the right type, rather than filling that slot with a new instance of my framework class, it's making it point to an existing worksheet instead, the equivalent of Set mcAppFramework = wksFoo which is a compiler error, as one might expect. Even more bizarrely, if I put a breakpoint on the offending line, edit the line, and then resume execution, it works. For example, I delete the word 'New' move off the line, move back, re-type 'New' and resume execution. This somehow 'fixes' the workbook and it works happily ever after, with the type of the variable in my watch window showing as csys_ApplicationFramework/csys_ApplicationFramework as I'd expect. This implies that manipulating the workbook through the PIA is somehow breaking it temporarily. All I'm doing in the PIA is opening the workbook, calling several macros using Excel.Application.Run(), and saving it again. I can post a few more details if anyone thinks that it's relevant. I don't know how VBA creates objects behind the scenes or how to debug this. I also don't know how the way the code executes can change without the code itself changing. As previously mentioned, VBA has frankly gone a bit squiffy on me... Any thoughts?

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  • Strange type-related error

    - by vsb
    I wrote following program: isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] primes = filter isPrime [1 .. ] it should construct list of prime numbers. But I got this error: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:3:16: Ambiguous type variable `a' in the constraints: `Floating a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `RealFrac a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `Integral a' arising from a use of `isPrime' at 7/main.hs:3:16-22 Possible cause: the monomorphism restriction applied to the following: primes :: [a] (bound at 7/main.hs:3:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Failed, modules loaded: none. If I specify signature for isPrime function explicitly: isPrime :: Integer -> Bool isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] I can't even compile isPrime function: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:2:45: No instance for (RealFrac Integer) arising from a use of `truncate' at 7/main.hs:2:45-61 Possible fix: add an instance declaration for (RealFrac Integer) In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] In a stmt of a list comprehension: i <- [2 .. truncate (sqrt x)] 7/main.hs:2:55: No instance for (Floating Integer) arising from a use of `sqrt' at 7/main.hs:2:55-60 Possible fix: add an instance declaration for (Floating Integer) In the first argument of `truncate', namely `(sqrt x)' In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] Failed, modules loaded: none. Can you help me understand, why am I getting these errors?

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  • PHP Multi-Domain Sessions; ini_set Not Working?

    - by SumWon
    Hello, I'm trying to set it up so if you log in to my website the session carries over to all sub-domains of my website. For example, if you go to domain.com and log in, then go to sub.domain.com, you'll already be logged in at sub.domain.com. To my understanding, you would want to use ini_set('session.cookie_domain','.domain.com') and then session_start(), then set your session variables, but this isn't working. Example of what I'm doing: Code for domain.com: <?php ini_set('session.cookie_domain','.domain.com'); session_start(); $_SESSION['variable'] = 1; ?> Code for sub.domain.com: <?php session_start(); echo $_SESSION['variable']; ?> But $_SESSION['variable'] isn't set. I've also tried using ini_set() in the sub.domain.com code, but it made no difference. I've verified that setting session.cookie_domain is working by using ini_get(). What am I doing wrong? Thanks!

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  • PGU HTML Renderer can't render most sites

    - by None
    I am trying to make a web browser using pygame. I am using PGU for html rendering. It works fine when I visit simple sites, like example.com, but when I try and load anything more complex that uses an html form, like google, I get this error: UnboundLocalError: local variable 'e' referenced before assignment I looked in the PGU html rendering file and found this code segment: def start_input(self,attrs): r = self.attrs_to_map(attrs) params = self.map_to_params(r) #why bother #params = {} type_,name,value = r.get('type','text'),r.get('name',None),r.get('value',None) f = self.form if type_ == 'text': e = gui.Input(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'radio': if name not in f.groups: f.groups[name] = gui.Group(name=name) g = f.groups[name] del params['name'] e = gui.Radio(group=g,**params) self.map_to_connects(e,r) self.item.add(e) if 'checked' in r: g.value = value elif type_ == 'checkbox': if name not in f.groups: f.groups[name] = gui.Group(name=name) g = f.groups[name] del params['name'] e = gui.Checkbox(group=g,**params) self.map_to_connects(e,r) self.item.add(e) if 'checked' in r: g.value = value elif type_ == 'button': e = gui.Button(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'submit': e = gui.Button(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'file': e = gui.Input(**params) self.map_to_connects(e,r) self.item.add(e) b = gui.Button(value='Browse...') self.item.add(b) def _browse(value): d = gui.FileDialog(); d.connect(gui.CHANGE,gui.action_setvalue,(d,e)) d.open(); b.connect(gui.CLICK,_browse,None) self._locals[r.get('id',None)] = e I got the error in the last line, because e wasn't defined. I am guessing the reason for this is that the if statement that checks the type of the input and creates the e variable didn't match anything. I added a line to print the _type variable and I got 'hidden' when i tried google and apple. Is there any way to render form items that have the type 'hidden' with PGU?

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  • What does the Asterisk * mean in Objective-C?

    - by Thanks
    Is it true, that the Asterisk always means "Hey, that is a pointer!" And an Pointer always holds an memory adress? (Yes I know for the exception that a * is used for math operation) For Example: NSString* myString; or SomeClass* thatClass; or (*somePointerToAStruct).myStructComponent = 5; I feel that there is more I need to know about the Asterirsk (*) than that I use it when defining an Variable that is a pointer to a class. Because sometimes I already say in the declaration of an parameter that the Parameter variable is a pointer, and still I have to use the Asterisk in front of the Variable in order to access the value. That recently happened after I wanted to pass a pointer of an struct to a method in a way like [myObj myMethod:&myStruct], I could not access a component value from that structure even though my method declaration already said that there is a parameter (DemoStruct*)myVar which indeed should be already known as a pointer to that demostruct, still I had always to say: "Man, compiler. Listen! It IIISSS a pointer:" and write: (*myVar).myStructComponentX = 5; I really really really do not understand why I have to say that twice. And only in this case. When I use the Asterisk in context of an NSString* myString then I can just access myString however I like, without telling the compiler each time that it's a pointer. i.e. like using *myString = @"yep". It just makes no sense to me.

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • templated method on T inside a templated class on TT : Is that possible/correct.

    - by paercebal
    I have a class MyClass which is templated on typename T. But inside, I want a method which is templated on another type TT (which is unrelated to T). After reading/tinkering, I found the following notation: template <typename T> class MyClass { public : template<typename TT> void MyMethod(const TT & param) ; } ; For stylistic reasons (I like to have my templated class declaration in one header file, and the method definitions in another header file), I won't define the method inside the class declaration. So, I have to write it as: template <typename T> // this is the type of the class template <typename TT> // this is the type of the method void MyClass<T>::MyMethod(const TT & param) { // etc. } I knew I had to "declare" the typenames used in the method, but didn't know how exactly, and found through trials and errors. The code above compiles on Visual C++ 2008, but: Is this the correct way to have a method templated on TT inside a class templated on T? As a bonus: Are there hidden problems/surprises/constraints behind this kind of code? (I guess the specializations can be quite amusing to write)

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  • I can't seem to figure out type variables mixed with classes.

    - by onmach
    I pretty much understand 3/4 the rest of the language, but every time I dip my feet into using classes in a meaningful way in my code I get permantently entrenched. Why doesn't this extremely simple code work? data Room n = Room n n deriving Show class HasArea a where width :: (Num n) => a -> n instance (Num n) => HasArea (Room n) where width (Room w h) = w So, room width is denoted by ints or maybe floats, I don't want to restrict it at this point. Both the class and the instance restrict the n type to Nums, but it still doesn't like it and I get this error: Couldn't match expected type `n1' against inferred type `n' `n1' is a rigid type variable bound by the type signature for `width' at Dungeon.hs:11:16 `n' is a rigid type variable bound by the instance declaration at Dungeon.hs:13:14 In the expression: w In the definition of `width': width (Room w h) = w In the instance declaration for `HasArea (Room n)' So it tells me the types doesn't match, but it doesn't tell me what types it thinks they are, which would be really helpful. As a side note, is there any easy way to debug an error like this? The only way I know to do it is to randomly change stuff until it works.

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  • Template access of symbol in unnamed namespace

    - by Fred Larson
    We are upgrading our XL C/C++ compiler from V8.0 to V10.1 and found some code that is now giving us an error, even though it compiled under V8.0. Here's a minimal example: test.h: #include <iostream> #include <string> template <class T> void f() { std::cout << TEST << std::endl; } test.cpp: #include <string> #include "test.h" namespace { std::string TEST = "test"; } int main() { f<int>(); return 0; } Under V10.1, we get the following error: "test.h", line 7.16: 1540-0274 (S) The name lookup for "TEST" did not find a declaration. "test.cpp", line 6.15: 1540-1303 (I) "std::string TEST" is not visible. "test.h", line 5.6: 1540-0700 (I) The previous message was produced while processing "f<int>()". "test.cpp", line 11.3: 1540-0700 (I) The previous message was produced while processing "main()". We found a similar difference between g++ 3.3.2 and 4.3.2. I also found in g++, if I move the #include "test.h" to be after the unnamed namespace declaration, the compile error goes away. So here's my question: what does the Standard say about this? When a template is instantiated, is that instance considered to be declared at the point where the template itself was declared, or is the standard not that clear on this point? I did some looking though the n2461.pdf draft, but didn't really come up with anything definitive.

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