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• How to implement a private virtual function within derived classes?

  - by Dane

  Hi, I know why I want to use private virtual functions, but how exactly can I implement them? For example: class Base{ [...] private: virtual void func() = 0; [...] } class Derived1: puplic Base{ void func() { //short implementation is ok here } } class Derived2: puplic Base{ void func(); //long implementation elsewhere (in cpp file) } [...] void Derived2::func() { //long implementation } The first version is ok but not always possible. Isn't the second version simply name hiding? How do you define the Base::func() of Derived2, if you cannot do it within the class declaration of Dereived2? Thanks

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• Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

  - by user1459698

  I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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• Store data in an inconvenient table or create a derived table?

  - by user1705685

  I have a certain predefined database structure that I am stuck with. The question is whether this structure is OK for ORM or I whether should add a processing layer that would create a more convenient structure every time something is inserted into the original DB. To simplify, here's what it kind of looks like. I have a person table: PersonId Name And I have a properties table: PersonId PropertyType PropertyValue So, for person John Doe... (1, 'John Doe') ...I could have three properties: (1, 'phone', '555-55-55'), (1, 'email', '[email protected]), (1, 'type', 'employee') By using ORM I would like to get a "person" object that would have properties "name", "phone", "email", "type". Can Propel do that? How efficient is it? Is it a better idea to create a table with columns "phone", "email", "type" and fill it automatically as new rows are inserted into the properties table?

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• Error while calling a virtual function that is defined in Derived class but not present in Base clas

  - by sandeep

  #include<iostream.h> class A{ public: virtual void fun() {cout<<"A::fun()"; } }; class B : public A { public: virtual void fun() {cout<<"B::fun()"; } virtual void func() {cout<<"B::func"; } }; int main() { A *obj1=new B; obj1->fun(); obj1->func(); }

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• will destroyed() be emitted if the constructor of a class derived from QObject throws?

  - by PorkyBrain

  Ive seen Qt GUI syntax like the following all over the place: myDialog::myDialog(QWidget *parent, Qt::WFlags flags):QDialog(parent, flags) { QPushButton *button = new QPushButton("&Download", this); QVBoxLayout *layout = new QVBoxLayout(this); //something that can throw here layout ->addWidget(button ); setLayout(layout); } I've always wondered if this can leak in the event of an exception because the "this" I'm giving as a parent to button and layout is not fully constructed so it might not destroy its children. I tried it out in MSVC2010 Qt4.8.3 and it looks like as soon as the base QObject class is fully created (which is done first of course) it is ok to pass "this" to other objects in the constructor, they will destroyed correctly. I haven't found the spot in the Qt docs guaranteeing this though, can someone point me to it so I have assurance that this will not change in the future?

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• Why can't I enforce derived classes to have parameterless constructors?

  - by FrisbeeBen

  I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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• Write a program for a report derived from the data in the data file JEWELRY. The data is to be input

  - by Taylor

  here is the JEWELRY file 0011 Money_Clip 2.000 50.00 Other 0035 Paperweight 1.625 175.00 Other 0457 Cuff_Bracelet 2.375 150.00 Bracelet 0465 Links_Bracelet 7.125 425.00 Bracelet 0585 Key_Chain 1.325 50.00 Other 0595 Cuff_Links 0.625 525.00 Other 0935 Royale_Pendant 0.625 975.00 Pendant 1092 Bordeaux_Cross 1.625 425.00 Cross 1105 Victory_Medallion 0.875 30.00 Pendant 1111 Marquis_Cross 1.375 70.00 Cross 1160 Christina_Ring 0.500 175.00 Ring 1511 French_Clips 0.687 375.00 Other 1717 Pebble_Pendant 1.250 45.00 Pendant 1725 Folded_Pendant 1.250 45.00 Pendant 1730 Curio_Pendant 1.063 275.00 Pendant this is the program i have used #include <iostream> #include <string> #include <iomanip> #include <fstream> using namespace std; struct productJewelry { string name; double amount; int itemCode; double size; string group; }; int main() { // declare variables ifstream inFile; int count=0; int x=0; productJewelry product[50]; inFile.open("jewelry.txt"); // file must be in same folder if (inFile.fail()) cout << "failed"; cout << fixed << showpoint; // fixed format, two decimal places cout << setprecision(2); while (inFile.peek() != EOF) { // cout << count << " : "; count++; inFile>> product[x].itemCode; inFile>> product[x].name; inFile>> product[x].size; inFile>> product[x].amount; inFile>> product[x].group; // cout << product[x].itemCode << ", " << product[x].name << ", "<< product[x].size << ", " << product[x].amount << endl; x++; if (inFile.peek() == '\n') inFile.ignore(1, '\n'); } inFile.close(); string temp; bool swap; do { swap = false; for (int x=0; x<count;x++) { if (product[x].name>product[x+1].name) { //these 3 lines are to swap elements in array temp=product[x].name; product[x].name=product[x+1].name; product[x+1].name=temp; swap=true; } } } while (swap); for (x=0; x< count; x++) { //cout<< product[x].itemCode<<" "; //cout<< product[x].name <<" "; //cout<< product[x].size <<" "; //cout<< product[x].amount<<" "; //cout<< product[x].group<<" "<<endl; } system("pause"); // to freeze Dev-c++ output screen return 0; } // end main

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• Why delegate types are derived from MulticastDelegate class why not it directly derive from Delegate class?

  - by Vijay

  I have a very basic question regarding delegate types. I compared the memebers of Delegate and MulticastDelegate classes in object browser and I couldn't find any new additional member present in MulticastDelegate. I also noticed that the Delegate class has GetInvocationList virtual method. So I assume that the Delegate class should have the capability to hold references to multiple methods. If my assumption is correct I wonder why not custom delegate types directly derive from the Delegate class instead of MulticastDelegate class. Not sure what I am missing here. Please help me understand the difference.

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• Windows Azure: General Availability of Web Sites + Mobile Services, New AutoScale + Alerts Support, No Credit Card Needed for MSDN

  - by ScottGu

  This morning we released a major set of updates to Windows Azure.  These updates included: Web Sites: General Availability Release of Windows Azure Web Sites with SLA Mobile Services: General Availability Release of Windows Azure Mobile Services with SLA Auto-Scale: New automatic scaling support for Web Sites, Cloud Services and Virtual Machines Alerts/Notifications: New email alerting support for all Compute Services (Web Sites, Mobile Services, Cloud Services, and Virtual Machines) MSDN: No more credit card requirement for sign-up All of these improvements are now available to use immediately (note: some are still in preview).  Below are more details about them. Web Sites: General Availability Release of Windows Azure Web Sites I’m incredibly excited to announce the General Availability release of Windows Azure Web Sites. The Windows Azure Web Sites service is perfect for hosting a web presence, building customer engagement solutions, and delivering business web apps.  Today’s General Availability release means we are taking off the “preview” tag from the Free and Standard (formerly called reserved) tiers of Windows Azure Web Sites.  This means we are providing: A 99.9% monthly SLA (Service Level Agreement) for the Standard tier Microsoft Support available on a 24x7 basis (with plans that range from developer plans to enterprise Premier support) The Free tier runs in a shared compute environment and supports up to 10 web sites. While the Free tier does not come with an SLA, it works great for rapid development and testing and enables you to quickly spike out ideas at no cost. The Standard tier, which was called “Reserved” during the preview, runs using dedicated per-customer VM instances for great performance, isolation and scalability, and enables you to host up to 500 different Web sites within them.  You can easily scale your Standard instances on-demand using the Windows Azure Management Portal.  You can adjust VM instance sizes from a Small instance size (1 core, 1.75GB of RAM), up to a Medium instance size (2 core, 3.5GB of RAM), or Large instance (4 cores and 7 GB RAM).  You can choose to run between 1 and 10 Standard instances, enabling you to easily scale up your web backend to 40 cores of CPU and 70GB of RAM: Today’s release also includes general availability support for custom domain SSL certificate bindings for web sites running using the Standard tier. Customers will be able to utilize certificates they purchase for their custom domains and use either SNI or IP based SSL encryption. SNI encryption is available for all modern browsers and does not require an IP address.  SSL certificates can be used for individual sites or wild-card mapped across multiple sites (we charge extra for the use of a SSL cert – but the fee is per-cert and not per site which means you pay once for it regardless of how many sites you use it with).  Today’s release also includes the following new features: Auto-Scale support Today’s Windows Azure release adds preview support for Auto-Scaling web sites.  This enables you to setup automatic scale rules based on the activity of your instances – allowing you to automatically scale down (and save money) when they are below a CPU threshold you define, and automatically scale up quickly when traffic increases.  See below for more details. 64-bit and 32-bit mode support You can now choose to run your standard tier instances in either 32-bit or 64-bit mode (previously they only ran in 32-bit mode).  This enables you to address even more memory within individual web applications. Memory dumps Memory dumps can be very useful for diagnosing issues and debugging apps. Using a REST API, you can now get a memory dump of your sites, which you can then use for investigating issues in Visual Studio Debugger, WinDbg, and other tools. Scaling Sites Independently Prior to today’s release, all sites scaled up/down together whenever you scaled any site in a sub-region. So you may have had to keep your proof-of-concept or testing sites in a separate sub-region if you wanted to keep them in the Free tier. This will no longer be necessary.  Windows Azure Web Sites can now mix different tier levels in the same geographic sub-region. This allows you, for example, to selectively move some of your sites in the West US sub-region up to Standard tier when they require the features, scalability, and SLA of the Standard tier. Full pricing details on Windows Azure Web Sites can be found here.  Note that the “Shared Tier” of Windows Azure Web Sites remains in preview mode (and continues to have discounted preview pricing).  Mobile Services: General Availability Release of Windows Azure Mobile Services I’m incredibly excited to announce the General Availability release of Windows Azure Mobile Services.  Mobile Services is perfect for building scalable cloud back-ends for Windows 8.x, Windows Phone, Apple iOS, Android, and HTML/JavaScript applications.  Customers We’ve seen tremendous adoption of Windows Azure Mobile Services since we first previewed it last September, and more than 20,000 customers are now running mobile back-ends in production using it.  These customers range from startups like Yatterbox, to university students using Mobile Services to complete apps like Sly Fox in their spare time, to media giants like Verdens Gang finding new ways to deliver content, and telcos like TalkTalk Business delivering the up-to-the-minute information their customers require.  In today’s Build keynote, we demonstrated how TalkTalk Business is using Windows Azure Mobile Services to deliver service, outage and billing information to its customers, wherever they might be. Partners When we unveiled the source control and Custom API features I blogged about two weeks ago, we enabled a range of new scenarios, one of which is a more flexible way to work with third party services.  The following blogs, samples and tutorials from our partners cover great ways you can extend Mobile Services to help you build rich modern apps: New Relic allows developers to monitor and manage the end-to-end performance of iOS and Android applications connected to Mobile Services. SendGrid eliminates the complexity of sending email from Mobile Services, saving time and money, while providing reliable delivery to the inbox. Twilio provides a telephony infrastructure web service in the cloud that you can use with Mobile Services to integrate phone calls, text messages and IP voice communications into your mobile apps. Xamarin provides a Mobile Services add on to make it easy building cross-platform connected mobile aps. Pusher allows quickly and securely add scalable real-time messaging functionality to Mobile Services-based web and mobile apps. Visual Studio 2013 and Windows 8.1 This week during //build/ keynote, we demonstrated how Visual Studio 2013, Mobile Services and Windows 8.1 make building connected apps easier than ever. Developers building Windows 8 applications in Visual Studio can now connect them to Windows Azure Mobile Services by simply right clicking then choosing Add Connected Service. You can either create a new Mobile Service or choose existing Mobile Service in the Add Connected Service dialog. Once completed, Visual Studio adds a reference to Mobile Services SDK to your project and generates a Mobile Services client initialization snippet automatically. Add Push Notifications Push Notifications and Live Tiles are a key to building engaging experiences. Visual Studio 2013 and Mobile Services make it super easy to add push notifications to your Windows 8.1 app, by clicking Add a Push Notification item: The Add Push Notification wizard will then guide you through the registration with the Windows Store as well as connecting your app to a new or existing mobile service. Upon completion of the wizard, Visual Studio will configure your mobile service with the WNS credentials, as well as add sample logic to your client project and your mobile service that demonstrates how to send push notifications to your app. Server Explorer Integration In Visual Studio 2013 you can also now view your Mobile Services in the the Server Explorer. You can add tables, edit, and save server side scripts without ever leaving Visual Studio, as shown on the image below: Pricing With today’s general availability release we are announcing that we will be offering Mobile Services in three tiers – Free, Standard, and Premium.  Each tier is metered using a simple pricing model based on the # of API calls (bandwidth is included at no extra charge), and the Standard and Premium tiers are backed by 99.9% monthly SLAs.  You can elastically scale up or down the number of instances you have of each tier to increase the # of API requests your service can support – allowing you to efficiently scale as your business grows. The following table summarizes the new pricing model (full pricing details here):   You can find the full details of the new pricing model here. Build Conference Talks The //BUILD/ conference will be packed with sessions covering every aspect of developing connected applications with Mobile Services. The best part is that, even if you can’t be with us in San Francisco, every session is being streamed live. Be sure not to miss these talks: Mobile Services – Soup to Nuts — Josh Twist Building Cross-Platform Apps with Windows Azure Mobile Services — Chris Risner Connected Windows Phone Apps made Easy with Mobile Services — Yavor Georgiev Build Connected Windows 8.1 Apps with Mobile Services — Nick Harris Who’s that user? Identity in Mobile Apps — Dinesh Kulkarni Building REST Services with JavaScript — Nathan Totten Going Live and Beyond with Windows Azure Mobile Services — Kirill Gavrylyuk , Paul Batum Protips for Windows Azure Mobile Services — Chris Risner AutoScale: Dynamically scale up/down your app based on real-world usage One of the key benefits of Windows Azure is that you can dynamically scale your application in response to changing demand. In the past, though, you have had to either manually change the scale of your application, or use additional tooling (such as WASABi or MetricsHub) to automatically scale your application. Today, we’re announcing that AutoScale will be built-into Windows Azure directly.  With today’s release it is now enabled for Cloud Services, Virtual Machines and Web Sites (Mobile Services support will come soon). Auto-scale enables you to configure Windows Azure to automatically scale your application dynamically on your behalf (without any manual intervention) so you can achieve the ideal performance and cost balance. Once configured it will regularly adjust the number of instances running in response to the load in your application. Currently, we support two different load metrics: CPU percentage Storage queue depth (Cloud Services and Virtual Machines only) We’ll enable automatic scaling on even more scale metrics in future updates. When to use Auto-Scale The following are good criteria for services/apps that will benefit from the use of auto-scale: The service/app can scale horizontally (e.g. it can be duplicated to multiple instances) The service/app load changes over time If your app meets these criteria, then you should look to leverage auto-scale. How to Enable Auto-Scale To enable auto-scale, simply navigate to the Scale tab in the Windows Azure Management Portal for the app/service you wish to enable.  Within the scale tab turn the Auto-Scale setting on to either CPU or Queue (for Cloud Services and VMs) to enable Auto-Scale.  Then change the instance count and target CPU settings to configure the Auto-Scale ranges you want to maintain. The image below demonstrates how to enable Auto-Scale on a Windows Azure Web-Site.  I’ve configured the web-site so that it will run using between 1 and 5 VM instances.  The exact # used will depend on the aggregate CPU of the VMs using the 40-70% range I’ve configured below.  If the aggregate CPU goes above 70%, then Windows Azure will automatically add new VMs to the pool (up to the maximum of 5 instances I’ve configured it to use).  If the aggregate CPU drops below 40% then Windows Azure will automatically start shutting down VMs to save me money: Once you’ve turned auto-scale on, you can return to the Scale tab at any point and select Off to manually set the number of instances. Using the Auto-Scale Preview With today’s update you can now, in just a few minutes, have Windows Azure automatically adjust the number of instances you have running  in your apps to keep your service performant at an even better cost. Auto-scale is being released today as a preview feature, and will be free until General Availability. During preview, each subscription is limited to 10 separate auto-scale rules across all of the resources they have (Web sites, Cloud services or Virtual Machines). If you hit the 10 limit, you can disable auto-scale for any resource to enable it for another. Alerts and Notifications Starting today we are now providing the ability to configure threshold based alerts on monitoring metrics. This feature is available for compute services (cloud services, VM, websites and mobiles services). Alerts provide you the ability to get proactively notified of active or impending issues within your application.  You can define alert rules for: Virtual machine monitoring metrics that are collected from the host operating system (CPU percentage, network in/out, disk read bytes/sec and disk write bytes/sec) and on monitoring metrics from monitoring web endpoint urls (response time and uptime) that you have configured. Cloud service monitoring metrics that are collected from the host operating system (same as VM), monitoring metrics from the guest VM (from performance counters within the VM) and on monitoring metrics from monitoring web endpoint urls (response time and uptime) that you have configured. For Web Sites and Mobile Services, alerting rules can be configured on monitoring metrics from monitoring endpoint urls (response time and uptime) that you have configured. Creating Alert Rules You can add an alert rule for a monitoring metric by navigating to the Setting -> Alerts tab in the Windows Azure Management Portal. Click on the Add Rule button to create an alert rule. Give the alert rule a name and optionally add a description. Then pick the service which you want to define the alert rule on: The next step in the alert creation wizard will then filter the monitoring metrics based on the service you selected:   Once created the rule will show up in your alerts list within the settings tab: The rule above is defined as “not activated” since it hasn’t tripped over the CPU threshold we set.  If the CPU on the above machine goes over the limit, though, I’ll get an email notifying me from an Windows Azure Alerts email address ([email protected]). And when I log into the portal and revisit the alerts tab I’ll see it highlighted in red.  Clicking it will then enable me to see what is causing it to fail, as well as view the history of when it has happened in the past. Alert Notifications With today’s initial preview you can now easily create alerting rules based on monitoring metrics and get notified on active or impending issues within your application that require attention. During preview, each subscription is limited to 10 alert rules across all of the services that support alert rules. No More Credit Card Requirement for MSDN Subscribers Earlier this month (during TechEd 2013), Windows Azure announced that MSDN users will get Windows Azure Credits every month that they can use for any Windows Azure services they want. You can read details about this in my previous Dev/Test blog post. Today we are making further updates to enable an easier Windows Azure signup for MSDN users. MSDN users will now not be required to provide payment information (e.g. no credit card) during sign-up, so long as they use the service within the included monetary credit for the billing period. For usage beyond the monetary credit, they can enable overages by providing the payment information and remove the spending limit. This enables a super easy, one page sign-up experience for MSDN users.  Simply sign-up for your Windows Azure trial using the same Microsoft ID that you use to manage your MSDN account, then complete the one page sign-up form below and you will be able to spend your free monthly MSDN credits (up to $150 each month) on any Windows Azure resource for dev/test:   This makes it trivially easy for every MDSN customer to start using Windows Azure today.  If you haven’t signed up yet, I definitely recommend checking it out. Summary Today’s release includes a ton of great features that enable you to build even better cloud solutions.  If you don’t already have a Windows Azure account, you can sign-up for a free trial and start using all of the above features today.  Then visit the Windows Azure Developer Center to learn more about how to build apps with it. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• Why `A & a = a` is valid?

  - by psaghelyi

  #include <iostream> #include <assert.h> using namespace std; struct Base { Base() : m_member1(1) {} Base(const Base & other) { assert(this != &other); // this should trigger m_member1 = other.m_member1; } int m_member1; }; struct Derived { Derived(Base & base) : m_base(m_base) {} // m_base(base) Base & m_base; }; void main() { Base base; Derived derived(base); cout << derived.m_base.m_member1 << endl; // crashes here } The above example is a synthesized version of a mistyped constructor. I used reference at the class member Derived::m_base because I wanted to make sure that the member will be initialized as the constructor had called. One problem is that nor GCC nor MSVC gives me a warning at m_base(m_base). But the more serious for me is that the assert finds everything fine and the application crashes later (sometimes far away from the mistake). Question: Is there any way to indicate such mistakes?

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• Python base classes share attributes?

  - by tad

  Code in test.py: class Base(object): def __init__(self, l=[]): self.l = l def add(self, num): self.l.append(num) def remove(self, num): self.l.remove(num) class Derived(Base): def __init__(self, l=[]): super(Derived, self).__init__(l) Python shell session: Python 2.6.5 (r265:79063, Apr 1 2010, 05:22:20) [GCC 4.4.3 20100316 (prerelease)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import test >>> a = test.Derived() >>> b = test.Derived() >>> a.l [] >>> b.l [] >>> a.add(1) >>> a.l [1] >>> b.l [1] >>> c = test.Derived() >>> c.l [1] I was expecting "C++-like" behavior, in which each derived object contains its own instance of the base class. Is this still the case? Why does each object appear to share the same list instance?

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• Usage of CRTP in a call chain

  - by fhw72

  In my widget library I'd like to implement some kind of call chain to initialize a user supplied VIEW class which might(!) be derived from another class which adds some additional functionality like this: #include <iostream> template<typename VIEW> struct App { VIEW view; void init() {view.initialize(); } }; template<typename DERIVED> struct SpecializedView { void initialize() { std::cout << "SpecializedView" << std::endl; static_cast<DERIVED*>(this)->initialize(); } }; struct UserView : SpecializedView<UserView> { void initialize() {std::cout << "UserView" << std::endl; } }; int _tmain(int argc, _TCHAR* argv[]) { // Cannot be altered to: App<SpecializedView<UserView> > app; App<UserView> app; app.init(); return 0; } Is it possible to achieve some kind of call chain (if the user supplied VIEW class is derived from "SpecializedView") such that the output will be: console output: SpecializedView UserView Of course it would be easy to instantiate variable app with the type derived from but this code is hidden in the library and should not be alterable. In other words: The library code should only get the user derived type as parameter.

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• Automatically Applying Security Updates for AWS Elastic Beanstalk

  - by Eric Anderson

  I've been a fan of Heroku since it's earliest days. But I like the fact that AWS Elastic Beanstalk gives you more control over the characteristics of the instances. One thing I love about Heroku is the fact that I can deploy an app and not worry about managing it. I am assuming Heroku is ensuring all OS security updates are timely applied. I just need to make sure my app is secure. My initial research on Beanstalk shows that although it builds and configures the instances for you, after that it moves to a more manual management process. Security updates won't automatically be applied to the instances. It seems there are two areas of concerns: New AMI releases - As new AMI releases hit it seems we would want to run the latest (presumably most secure). But my research seems to indicate you need to manually launch a new setup to see the latest AMI version and then create a new environment to use that new version. Is there a better automated way of rotating your instances into new AMI releases? In between releases there will be security updates released for packages. Seems we want to upgrade those as well. My research seems to indicate people install commands to occasionally run a yum update. But since new instances are created/destroyed based on usage it seems that the new instances would not always have the updates (i.e. the time between the instance creation and the first yum update). So occasionally you will have instances that aren't patched. And you are also going to have instances constantly patching themselves until the new AMI release is applied. My other concern is that perhaps these security updates haven't gone through Amazon's own review (like the AMI releases do) and it might break my app to automatically update them. I know Dreamhost once had a 12 hour outage because they were applying debian updates completely automatically without any review. I want to make sure the same thing doesn't happen to me. So my question is does Amazon provide a way to offer fully managed PaaS like Heroku? Or is AWS Elastic Beanstalk really more of just a install script and after that you are on your own (other than the monitoring and deployment tools they provide)?

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• Consolidating files in a single directory before you link them into the final executable

  - by David

  I am working on Solaris 10, Sun Studio 11. I am refactoring some old code, and trying to write unit tests for them. My make file looks like: my_model.o:my_model.cc CC -c my_model.cc -I/../../include -library=stlport4 -instances=extern unit_test: unit_test.o my_model.o symbol_dictionary.o CC -o unit_test unit_test.o my_model.o symbol_dictionary.o -I../../include \ -library=stlport4 -instances=extern unit_test.o: unit_test.cc CC -c unit_test.cc -I/../../include -library=stlport4 -instances=extern symbol_dictionary.o: cd ../../test-fixtures && ($MAKE) symbol_dictionary.o mv ../../test-fixtures/symbol_dictionary.o . In the ../../test-fixtures makefile, I have the following target: symbol_dictionary.o: CC -c symbol_dictionary.cc -I/../../include -library=stlport4 -instances=extern I do the instances=extern because I had linking problems before, and this was the recommended solution. The consequence is in each directory that is being compiled, a SunWS_Cache directory is created to store the template instances. This is the long way to get to this question. Is it a standard practice to consolidate object files in a single directory before you link them?

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• How to avoid general names for abstract classes?

  - by djechlin

  In general it's good to avoid words like "handle" or "process" as part of routine names and class names, unless you are dealing with (e.g.) file handles or (e.g.) unix processes. However abstract classes often don't really know what they're going to do with something besides, say, process it. In my current situation I have an "EmailProcessor" that logs into a user's inbox and processes messages from it. It's not really clear to me how to give this a more precise name, although I've noticed the following style matter arises: better to treat derived classes as clients and named the base class by the part of the functionality it implements? Gives it more meaning but will violate is-a. E.g. EmailAcquirer would be a reasonable name since it's acquiring for the derived class, but the derived class won't be acquiring for anyone. Or just really vague name since who knows what the derived classes will do. However "Processor" is still too general since it's doing many relevant operations, like logging in and using IMAP. Any way out of this dilemma? Problem is more evident for abstract methods, in which you can't really answer the question "what does this do?" because the answer is simply "whatever the client wants."

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• License compatibility question

  - by Ivaylo Slavov

  I have a question regarding software licenses. I plan to put a license to a framework that I have written. My intention is that the license should be open, in order to maintain a community. Also I want to control when a new version is released and which changes will be included. The license should allow the framework to be used with commercial products, therefore respecting their own license. I have done some quick research and I decided to double license my work under the Apache License 2.0 (ASL) and Eclipse Public License (EPL). My point is that the EPL will provide me the ability to control the release cycle as well as the contributions to the project and the Apache license will take care for any patents a 3rd party might want to use in a derived work. Also both are open licenses. My question is related to the GLP and LGPL licenses. If I have the above licenses to my framework, will it be possible and legal, for someone to create a derived work of my framework, that is also a derived work of, or links a library that is under the LGPL license? Thanks in advance. EDIT: To be clear I will explain how I expect things to work. The framework will define some common API for certain functionalities as well as a Wrapper class that will invoke an implementation of that API. The Wrapper will be part of the framework, but it will internally call the actual implementation. This implementation should be in a separate library, and such libraries I would like to be developed and maintained by community. Surely the community will have to access the framework but I want to limit changes to the framework by the community but I want to provide freedom for any API implementation (a derived work of the framework). The framework will enable flexible configuration mechanisms that will tell which implementation of an API will be used.

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• How can I port msvc++ code with non-dependent names in templates to Linux?

  - by user352382

  I can deal with porting platform dependent functions. I have a problem that the compilers I tried on Linux (clang and g++) do not accept the following code, while the msvc++ compiler does: template <class T> class Base { protected: T Value; }; template <class T> class Derived : public Base<T> { public: void setValue(const T& inValue){ Value = inValue; } }; int main(int argc, char const *argv[]) { Derived<int> tmp; tmp.setValue(0); return 0; } g++ error: main.cpp: In member function ‘void Derived<T>::setValue(const T&)’: main.cpp:11:3: error: ‘Value’ was not declared in this scope I believe this due to the use of a non-dependent name (Value) in the second class. More information. The problem is that I have a very large code base, in which this type of code is used very often. I understand that it is wrong when looking at the standard. However it is very convenient not having to write this-> or Base<T>:: in front of every use of Value. Even writing using Base<T>::Value; at the start of the derived class is problematic when you use ~20 members of the base class. So my question is: are there compilers for Linux that allow this kind of code (with or without extra compiler switches)? Or are there small modifications that will allow this code to compile on Linux?

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• Can I use a class as an object in C# to create instances of that class?

  - by Troy

  I'm writing a fairly uncomplicated program which can "connect" to several different types of data sources including text files and various databases. I've decided to implement each of these connection types as a class inherited from an interface I called iConnection. So, for example, I have TextConnection, MySQLConnection, &c... as classes. In another static class I've got a dictionary with human-readable names for these connections as keys. For the value of each dictionary entry, I want the class itself. That way, I can do things like: newConnection = new dict[connectionTypeString](); Is there a way to do something like this? I'm fairly new to C# so I'd appreciate any help.

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• Windows Azure Upgrade Domain

  - by kaleidoscope

  Windows Azure automatically divides your role instances into some “logical” domains called upgrade domains. During upgrade, Azure is updating these domains one by one. This is a by design behavior to avoid nasty situations. Some of the last feature additions and enhancements on the platform was the ability to notify your role instances in case of “environment” changes, like adding or removing being most common. In such case, all your roles get a notification of this change. Imagine if you had 50 or 60 role instances, getting notified all at once and start doing various actions to react to this change. It will be a complete disaster for your service. The way to address this problem is upgrade domains. During upgrade Windows Azure updates them one by one and only the associated role instances to a specific domain get notified of the changes taking place. Only a small number of your role instances will get notified, react and the rest will remain intact providing a seamless upgrade experience and no service disruption or downtime. http://www.kefalidis.me/archive/2009/11/27/windows-azure-ndash-what-is-an-upgrade-domain.aspx   Lokesh, M

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• MSSQL instance shuts down

  - by citronas

  I'm currently developing a new ASP.net project hosted on a Windows Server 2008 RC2 with an MSSQL 2008 Express Database. I have three SQL instances (for different purposes) running which currently all contain a single database. For apprently no reason, these instances tend to shut down after some days, for no apparent reason. There might be low or none traffic to these instances, because there might be some days in a row, where I can't develop. It now occured several times, that one or two of these three instances just shut down, so that I can't access the database, without manually starting the instance. I can't seem to find a event log entry for the shutdown, which is most likely because I just enabled logging (why is the default setting off?) So the questions are: * Why does a SQL instance shut down? (Is there such thing as a "Shut down instance after 3 days of inactivity"? * How can I achieve that the instances are running 24/7?

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• pyinstaller: 2 instances of my cherrypy app exe get executed.

  - by d.c

  I have a cherrypy app that I've made an exe with pyinstaller. now when I run the exe it loads itself twice into memory. Watching the taskmanager shows the first instance load into about 1k, then a second later a second instance of hte exe loads into about 3k ram. If I close the bigger one both processes die. If I close hte smaller one only that one dies. Loading the exe with subprocess, if I try to proc.kill(), it only kills the small one leaving the other running in memory. Is this a sideeffect of using cherrypy and pyinstaller together?

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• How to extend methods to a class not to its instances.

  - by Fraga

  Hi. Extending methods to any instance is really easy: public static string LeaveJustNumbers(this string text) { return Regex.Replace(text, @"[\D]", ""); } ... string JustNumbers = "A5gfb343j4".LeaveJustNumber(); But what if i want to extend methods to a sealed class like string, to work like: string.Format("Hi:{0}","Fraga"); Is there any way to do it?

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• Analyzing data from same tables in diferent db instances.

  - by Oscar Reyes

  Short version: How can I map two columns from table A and B if they both have a common identifier which in turn may have two values in column C Lets say: A --- 1 , 2 B --- ? , 3 C ----- 45, 2 45, 3 Using table C I know that id 2 and 3 belong to the same item ( 45 ) and thus "?" in table B should be 1. What query could do something like that? EDIT Long version ommited. It was really boring/confusing EDIT I'm posting some output here. From this query: select distinct( rolein) , activityin from taskperformance@dm_prod where activityin in ( select activityin from activities@dm_prod where activityid in ( select activityid from activities@dm_prod where activityin in ( select distinct( activityin ) from taskperformance where rolein = 0 ) ) ) I have the following parts: select distinct( activityin ) from taskperformance where rolein = 0 Output: http://question1337216.pastebin.com/f5039557 select activityin from activities@dm_prod where activityid in ( select activityid from activities@dm_prod where activityin in ( select distinct( activityin ) from taskperformance where rolein = 0 ) ) Output: http://question1337216.pastebin.com/f6cef9393 And finally: select distinct( rolein) , activityin from taskperformance@dm_prod where activityin in ( select activityin from activities@dm_prod where activityid in ( select activityid from activities@dm_prod where activityin in ( select distinct( activityin ) from taskperformance where rolein = 0 ) ) ) Output: http://question1337216.pastebin.com/f346057bd Take for instace activityin 335 from first query ( from taskperformance B) . It is present in actvities from A. But is not in taskperformace in A ( but a the related activities: 92, 208, 335, 595 ) Are present in the result. The corresponding role in is: 1

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• What are all the instances of syntactic sugar in Scala?

  - by Jackson Davis

  I decided to create this question to have a single source for all things syntactic sugar in Scala. I feel these details are some of the things most frustrating to starting users and are hard to search for since most/all of them are purely symbols and are thus hard to search for without knowing the name of the concept. TODO: implicit conversions _ syntax for anonymous functions Extractors(Unapply/UnapplySeq) Other things I'm forgetting

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• RESTful API design question - how should one allow users to create new resource instances?

  - by Tamás

  I'm working in a research group where we intend to publish implementations of some of the algorithms we develop on the web via a RESTful API. Most of these algorithms work on small to medium size datasets, and in many cases, a user of our services might want to run multiple queries (with different parameters) on the same dataset, so for me it seems reasonable to allow users to upload their datasets in advance and refer to them in their queries later. In this sense, a dataset could be a resource in my API, and an algorithm could be another. My question is: how should I let the users upload their own datasets? I cannot simply let users upload their data to /dataset/dataset_id as letting the users invent their own dataset_ids might result in ID collision and users overwriting each other's datasets by accident. (I believe one of the most frequently used dataset ID would be test). I think an ideal way would be to have a dedicated URL (like /dataset/upload) where users can POST their datasets and the response would contain a unique ID under which the dataset was stored, but I'm not sure that it does not violate the basic principles of REST. What is the preferred way of dealing with such scenarios?

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