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• static const double in c++

  - by Crystal

  Is this the proper way to use a static const variable? In my top level class (Shape) #ifndef SHAPE_H #define SHAPE_H class Shape { public: static const double pi; private: double originX; double originY; }; const double Shape::pi = 3.14159265; #endif And then later in a class that extends Shape, I use Shape::pi. I get a linker error. I moved the const double Shape::pi = 3.14... to the Shape.cpp file and my program then compiles. Why does that happen? thanks.

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• Understanding Nested If.. Else statements

  - by user1174762

  For some reason my PHP login script keeps returning "invalid email/password combination", yet i know I am entering the correct email and password. Does anyone see what I might be doing wrong? <?php $email= $_POST['email']; $password= $_POST['password']; if (!empty($email) && !empty($password)) { $connect= mysqli_connect("localhost", "root", "", "si") or die('error connecting with the database'); $query= "SELECT user_id, email, password FROM users WHERE email='$email' AND password='$password'"; $result= mysqli_query($connect, $query) or die('error with query'); if (mysqli_num_rows($result) == 1) { $row= mysqli_fetch_array($result); setcookie('user_id', $row['user_id']); echo "you are now logged in"; } else { echo "invalid username/password combination"; } } else { echo" you must fill out both username and password"; } ?>

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• Can I improve performance by refactoring SQL commands into C# classes?

  - by Matthew Jones

  Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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• Opening IProject properties when another (adaptable to IProject) object is selected

  - by Stan

  I have a custom view displaying a hierarchy model of the current project. The root element is of class MyProject which is my own class, but it represents one Eclipse IProject, and it's adaptable to IProject. I have a "properties" menu option in the popup menu for that view, and I'd like to open up IProject's properties when a MyProject object is selected. PropertyDialogAction only looks for property pages registered for MyProject and doesn't give me a chance to offer an adapter -- or, at least, I don't know how to offer one. What's the proper solution for this? In the meantime, I've overridden PropertyDialogAction to handle my class in the special way I require, but that seems like quite a kludge to get this done.

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• Program-wide data, C++

  - by bobobobo

  I'd like to make program-wide data in a C++ program. The easiest way to do it in C# is just public static members. C#: public static class DataContainer { public static Object data1 ; public static Object data2 ; } In C++ you can do the same thing C++ global data way#1: class DataContainer { public: static Object data1 ; static Object data2 ; } ; Object DataContainer::data1 ; Object DataContainer::data2 ; However there's also extern C++ global data way #2: class DataContainer { public: Object data1 ; Object data2 ; } ; extern DataContainer * dataContainer ; // instantiate in .cpp file Which is better, or possibly another way which I haven't thought about?

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• remove/restore elements, maintaining their events and element's children

  - by Emin

  I came to a situation where I need to edit the following in a way that, on some event (lets assume the 'click' event in this case) I need to remove (or unwrap?) the .container and the .header and have the .itemlist still visible/available on the page. And then, I need to restore .container and .header back again on some other event, while still maintain the event listeners on the a tags, and if possible, without removing the said items from the DOM. Is this possible? <ul class="container"> <li class="header"><a href="#">delete</a> | <a href="#">edit</a></li> <ul class="itemlist"> <li>some item</li> <li>some other item</li> </ul> </ul>

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• Java Enum Newbie Question

  - by ikurtz

  i have a situation where i need the Checker enum below used in multiple classes: package Sartre.Connect4; public enum Checker { EMPTY, RED, YELLOW } so i put the Checker in a Checker.java file and then from the classes that need it i simply do the following: example: public Cell(){ currentCell = Checker.EMPTY; } example: public Cell(Checker checker){ currentCell = checker; } and the code compiles fine and runs fine also. so what is my question? well being new to Java i am just wondering if the way i use Checker without encapsulating it in a class is a sound implementation? it may be because of The enum declaration defines a class (called an enum type). as noted in Java docs enum tutorial page. thank you for your insight into this matter.

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• fopen in C(Linux) returns "Too many open files"

  - by liv2hak

  static char filename[128] = "trace.txt"; g_file = fopen(filename, "w"); if(NULL == g_file) { printf("Cannot open file %s.error %s\n",filename,strerror(errno)); exit(1); } I am trying to open a empty text file named trace.txt in write mode (in my working directory.) The program is creating an empty file trace.txt in my directory.but the check (NULL == g_file) is returning true and it is returning error code 24 (Too many open files.).Any idea why this is.This is the first file I am opening in my program.

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• Shared WCF client code between .NET and Silverlight apps?

  - by Eduardo Scoz

  I'm developing a .NET application that will have both a WinForms and a Silverlight client. Although the majority of code will be in the server, I'll need to have quite a bit of logic in the clients as well, and I would like to keep the client library code the same. From what I could figure out so far, I need to have two different project types, a class library and a Silverlight class library, and link the files from one project to the other. This seems kind of lame, but it works for simple code. My problem, though, is that the code generated by the SVCUtil.exe to access WCF services is different from the code generated by the slsvcutil.exe, and the silverlight code is actually incompatible with the .NET one: I get a bunch of problems with the System.ServiceModel.Channel classes when I try to import the class into .NET. Has anybody done anything similar to this before? What am I doing wrong?

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• What is this Design Pattern?

  - by Can't Tell

  I read the Wikipedia articles on FactoryMethod and AbstractFactory but the following code doesn't seem to fit anywhere. Can someone explain to me what the following pattern is or if it is an anti-pattern? interace PaymentGateway{ void makePayment(); } class PaypalPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class AuthorizeNetPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class PaymentGatewayFacotry{ PaymentGateway createPaymentGateway(int gatewayId) { if(gatewayId == 1) return PaypalPaymentGateway(); else if(gatewayId == 2) return AuthorizeNetPaymentGateway(); } } Let's say the user selects the payment method using a radio button on an html page and the gatewayId is derived from the radio button value. I have seen code like this and thought it was the AbstractFactory pattern but after reading the Wikipedia article, I'm having doubts.

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• SQL returns non-array value in PHP

  - by DeadMG

  $request = 'SELECT * FROM flight WHERE Id = \''.$_SESSION['LFLightRadio'].'\''; $data = mysql_fetch_array(mysql_query($request, $SQL)); echo '<table class="table">'; foreach($data as $key => $value) { echo '<th class="head" align="center" height="19">'.$key.'</th>'; } echo '<tr>'; foreach($data as $key => $value) { echo '<td class="cell" align="center" height="19">'.$value.'</td>'; } echo '</tr></table>'; I know that the LFlightRadio value is set, and is a value returned by the Id value of a previously returned row from the flight database. So within "flight", a record definitely exists with this Id. But, this still gives me a non-array result, so that when I try to use foreach on it, it errors out. Suggestions?

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• Best way to map/join two autogenerated enums

  - by tomlip

  What is the best C++ (not C++11) way of joining two enums from autogenerated class similar to one presented below: namespace A { namespace B { ... class CarInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } class BikeInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } } } What is needed is unified enum State for both classes that is seen to outside world alongside with safe type conversion. The best and probably most straightforward way I came up with is to create external enum: enum State { Running, Stopped, Broken } together with conversion functions State stateEnumConv(A::B::CarInfo::State aState); State stateEnumConv(A::B::BikeInfo::State aState); A::B::CarInfo::State stateEnumConv(State aState); A::B::BikeInfo::State stateEnumConv(State aState); Direction into right approach is needed. Gosh coming from C I hate those long namespaces everywhere an I wish it could be only A::B level like in presented example. Four conversion functions seem redundant note that CarInfo::State and BikeInfo::State has same enum "members".

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• mysql conditional query - complicated!

  - by emre

  i want to get distinct values for a field, let say: field1... ok this needs a query like: "select distint(field1) from table" however for some records, field1 is empty and there is another column that is an alternative to field1, which is field2. now; for the records where field1 is empty i need to use the value of field2. i think i need sort of a conditional select statement with if control something like: "select distinct( (if(field1!='') field1 else field2) ) from table" but i have no idea on how to write it. any help is appricated...

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• Any way to set or overwrite the __line__ and __file__ metadata?

  - by charles.merriam

  I'm writing some code that needs to change function signatures. Right now, I'm using Simionato's FunctionMaker class, which uses the (hacky) inspect module, and does a compile. Unfortunately, this still loses the line and file metadata. Does anyone know: If it is possible to overwrite these values in some odd way? If hacking up a class with a complex getattribute() to intercept the values and also try to make the class looks like a function is any more possible than a moose with a flying nun hat? Is there an alternative to the (hacky) inspect module? PEP 362 is dead dead dead? I know decorators and cPickle users fight with this. What other situations is the read only metadata in people's way? I appreciate any insights. Thank you.

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• Preprocessor Conditionals

  - by Mike

  I was wondering if it would be possible to have a define which changes values at some point in the code be used in a conditional. Basically something like this: //////////////////////////////////////////// SomeFile.cpp #define SHUTDOWN false while(window->isOpen()) { if(SHUTDOWN) window->close(); // Rest of the main loop } //////////////////////////////////////////// SomeOtherFile.cpp if(Escape.isPressed()) { #undef SHUTDOWN #define SHUTDOWN true } Thus causing the app to close. If it's not, would having a function like RenderWindow* getWindow() { return window; } and then calling if(Escape.isPressed()) getWindow()->close(); The best way to do it? I'd rather not go that route because the classes that are calling the key event are members of the class controlling the main loop and the window, so I'd have to set pointers to the containing class in the smaller classes to call getWindow() and it just seems like a more complicated method. But if I can't do it with preprocessor directives I'll just have to use pointers to the parent class.

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• Can I improve performance by refactoring SQL commands into classes?

  - by Matthew Jones

  Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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• Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

  - by Shane MacLaughlin

  Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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• Emulator batteryService not working

  - by user568551

  So i've got a 1.6 emulator running. I have a receiver with action power connected and disconnected filters. when i connect to the emulator through telnet and issue the power ac on or power ac off command, logcat shows: 01-11 21:33:01.096: ERROR/BatteryService(67): Could not open '/sys/class/power_supply/usb/online' 01-11 21:33:01.104: ERROR/BatteryService(67): Could not open '/sys/class/power_supply/battery/batt_vol' 01-11 21:33:01.104: ERROR/BatteryService(67): Could not open '/sys/class/power_supply/battery/batt_temp' and my receiver does not get activated. It was working just fine yesterday and now it does not. I tried reinstalling the AVD, and also deleted and reinstalled the SDK from the SDK manager. Works fine in my 2.2 emulator. Any ideas?

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• Best indexing strategy for several varchar columns in Postgres

  - by Corey

  I have a table with 10 columns that need to be searchable (the table itself has about 20 columns). So the user will enter query criteria for at least one of the columns but possibly all ten. All non-empty criteria is then put into an AND condition Suppose the user provided non-empty criteria for column1 and column4 and column8 the query would be: select * from the_table where column1 like '%column1_query%' and column4 like '%column4_query%' and column8 like '%column8_query%' So my question is: am I better off creating 1 index with 10 columns? 10 indexes with 1 column each? Or do I need to find out what sets of columns are queried together frequently and create indexes for them (an index on cols 1,4 and 8 in the case above). If my understanding is correct a single index of 10 columns would only work effectively if all 10 columns are in the condition. Open to any suggestions here, additionally the rowcount of the table is only expected to be around 20-30K rows but I want to make sure any and all searches on the table are fast. Thanks!

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• When to trash hashmap contents to avoid performance degradation?

  - by Jack

  Hello, I'm woking on Java with a large (millions) hashmap that is actually built with a capacity of 10.000.000 and a load factor of .75 and it's used to cache some values since cached values become useless with time (not accessed anymore) but I can't remove useless ones while on the way I would like to entirely empty the cache when its performance starts to degrade. How can I decide when it's good to do it? For example, with 10 millions capacity and .75 should I empty it when it reaches 7.5 millions of elements? Because I tried various threshold values but I would like to have an analytic one. I've already tested the fact that emping it when it's quite full is a boost for perfomance (first 2-3 algorithm iterations after the wipe just fill it back, then it starts running faster than before the wipe) Thanks

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• Question about C# properties

  - by Impz0r

  Hey there, i bumped the other day into a little problem regarding C#'s properties. Let's say i do have this setup: public class Point { public float X; public float Y; } public class Control { protected Point m_Position = new Point(); public Position { get { return m_Position; } set { m_Position = value; } // reorganize internal structure.. reorganize(); } protected reorganize() { // do some stuff } } This is all fine, but when it comes to usage, i could write something like: Control myControl = new Control(); myControl.Position.X = 1.0f; The thing is, my Control class wont recognize that the Position has been changed because set hasn't been called. So i guess my question is, is there a way to make Control aware of any Position changes? Thanks in advance! Mfg Imp

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• java.text.DecimalFormat blank when zero?

  - by Eduardo

  Is it possible to show blank (empty string) when the number is zero (0)? (strict no zeros at left)

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• Cisco - Zone Policy Actions (pass, inspect, drop, log) - What is the difference?

  - by Jonathan Rioux

  Have these commands for instance: policy-map type inspect IN-OUT_PlcyMAP class type inspect IN-OUT_ClassMAP inspect <------ policy-map type inspect IN-OUT_PlcyMap class type inspect IN-OUT_ClassMAP pass <------ zone security INSIDE zone security OUTSIDE zone-pair security IN->OUT source INSIDE destination OUTSIDE service-policy type inspect IN-OUT_PlcyMAP What is the difference between "inspect", "pass", "drop", "log", and "reset ? I could not found any information on this on Google.

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• How to select all child elements of specified control using jQuery

  - by abatishchev

  I have a <table id="myTable"> with a number of child elements: <tr><td> <span class="mySpan" /> </td></tr> <tr><td> <span class="mySpan" /> </td></tr> <tr><td> <span class="mySpan" /> </td></tr> How to select all this spans using jQuery?

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• Remove C# attribute of a property dynamically

  - by SysAdmin

  Hi, I have a class with a set of properties As given below. class ContactInfo { [ReadOnly(true)] [Category("Contact Info")] public string Mobile { get; set; } [Category("Contact Info")] public string Name{ get; set; } } The objects of this class is being assigned to a property grid, so that the users can update an existing contact. you can see that Mobile is marked as ReadOnly. But, when I want to add an entirely new Contact, I would want the users to be able to edit the contact Mobile also. For that I need to remove the Readonly property dynamically from the Type, before assigning the object to the property grid. Is it possible?

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