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• Is there a way to create subdatabases as a kind of subfolders in sql server?

  - by user193655

  I am creating an application where there is main DB and where other data is stored in secondary databases. The secondary databases follow a "plugin" approach. I use SQL Server. A simple installation of the application will just have the mainDB, while as an option one can activate more "plug-ins" and for every plug-in there will be a new database. Now why I made this choice is because I have to work with an exisiting legacy system and this is the smartest thing I could figure to implement the plugin system. MainDB and Plugins DB have exactly the same schema (basically Plugins DB have some "special content", some important data that one can use as a kind of template - think to a letter template for example - in the application). Plugin DBs are so used in readonly mode, they are "repository of content". The "smart" thing is that the main application can also be used by "plugin writers", they just write a DB inserting content, and by making a backup of the database they creaetd a potential plugin (this is why all DBs has the same schema). Those plugins DB are downloaded from internet as there is a content upgrade available, every time the full PlugIn DB is destroyed and a new one with the same name is creaetd. This is for simplicity and even because the size of this DBs is generally small. Now this works, anyway I would prefer to organize the DBs in a kind of Tree structure, so that I can force the PlugIn DBs to be "sub-DBs" of the main application DB. As a workaround I am thinking of using naming rules, like: ApplicationDB (for the main application DB) ApplicationDB_PlugIn_N (for the N-th plugin DB) When I search for plugin 1 I try to connect to ApplicationDB_PlugIn_1, if I don't find the DB i raise an error. This situation can happen for example if som DBA renamed ApplicationDB_Plugin_1. So since those Plugin DBs are really dependant on ApplicationDB only I was trying to "do the subfolder trick". Can anyone suggest a way to do this? Can you comment on this self-made plugin approach I decribed above?

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• Get control in code from ControlTemplate By Name

  - by Polaris

  Hello. I have next control template in my WPF app. <Style TargetType="Label" x:Key="LabelStyle"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Label"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="40"/> <ColumnDefinition/> </Grid.ColumnDefinitions> <TextBox x:Name="MyTextBlock" Text="{TemplateBinding Content}" Height="20" HorizontalAlignment="Left" VerticalAlignment="Top" /> <Label Content="{TemplateBinding Content}" Grid.Column="1" Grid.Row="1"/> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> TextBox "MyTextBlock" is invisible in C# code of window. How can I access to this textblock in code

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• Need help optimizing this Django aggregate query

  - by Chris Lawlor

  I have the following model class Plugin(models.Model): name = models.CharField(max_length=50) # more fields which represents a plugin that can be downloaded from my site. To track downloads, I have class Download(models.Model): plugin = models.ForiegnKey(Plugin) timestamp = models.DateTimeField(auto_now=True) So to build a view showing plugins sorted by downloads, I have the following query: # pbd is plugins by download - commented here to prevent scrolling pbd = Plugin.objects.annotate(dl_total=Count('download')).order_by('-dl_total') Which works, but is very slow. With only 1,000 plugins, the avg. response is 3.6 - 3.9 seconds (devserver with local PostgreSQL db), where a similar view with a much simpler query (sorting by plugin release date) takes 160 ms or so. I'm looking for suggestions on how to optimize this query. I'd really prefer that the query return Plugin objects (as opposed to using values) since I'm sharing the same template for the other views (Plugins by rating, Plugins by release date, etc.), so the template is expecting Plugin objects - plus I'm not sure how I would get things like the absolute_url without a reference to the plugin object. Or, is my whole approach doomed to failure? Is there a better way to track downloads? I ultimately want to provide users some nice download statistics for the plugins they've uploaded - like downloads per day/week/month. Will I have to calculate and cache Downloads at some point? EDIT: In my test dataset, there are somewhere between 10-20 Download instances per Plugin - in production I expect this number would be much higher for many of the plugins.

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• SFINAE and detecting if a C++ function object returns void.

  - by Tom Swirly

  I've read the various authorities on this, include Dewhurst and yet haven't managed to get anywhere with this seemingly simple question. What I want to do is to call a C++ function object, (basically, anything you can call, a pure function or a class with ()), and return its value, if that is not void, or "true" otherwise. #include <stdio.h> struct Foo { void operator()() {} }; struct Bar { bool operator()() { return false; } }; Foo foo; Bar bar; bool baz() { return false; } void bang() {} const char* print(bool b) { printf(b ? "true, " : "false, "); } template <typename Functor> bool magicCallFunction(Functor f) { return true; // lots of template magic occurs here... } int main(int argc, char** argv) { print(magicCallFunction(foo)); print(magicCallFunction(bar)); print(magicCallFunction(baz)); print(magicCallFunction(bang)); printf("\n"); }

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• Get current node's local-name in XSL

  - by green67

  Here's the structure of my XML <FileRoot> <UserSet1> <User> <FirstName></FirstName> <LastName></LastName> </User> <User> <FirstName></FirstName> <LastName></LastName> </User> ... </UserSet1> <InactiveUsers> <User> <FirstName></FirstName> <LastName></LastName> </User> <User> <FirstName></FirstName> <LastName></LastName> </User> ... </InactiveUsers> </FileRoot> In my XSL template <xsl:template match="/*/*"> <File> <xsl attribute name="Name"> <xsl:value-of select="local-name(/*/*)"/> </xsl:attribute> </File> </xsl> After transforming, for both UserSet1 and InactiveUsers, gave me "UserSet1". The expected results should be "UserSet1" for UserSet1, and "InactiveUsers" for InactiveUsers. How do I correctly retrieve the value? Thanks

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• C++ traits question

  - by duli

  I have a templated class template <typename Data> class C { ..... } In most situations, I depend on the compiler to let me substitute types for Data. I call methods foo(), goo() on objects of type Data, so what I substitute needs to provide that. I now need to substitute int and string for my Data type. I do not want to specialize because the class is already too big and would require specializing each method (with only small code change). My options (please tell me if there are more) 1) I can provide wrapper classes around int and string which implement the methods foo(), goo() etc 2) provide a traits class traits that calls foo() or goo() on objects of classes that provide foo(),goo() (these are my present substitutable classes) and specialize these classes for int and string. Questions 1) what are the relative merits of 1 vs 2? 2) My traits classes will have static methods. Can a traits class have non-static methods as well? I see most traits classes define constants in the STL. 3) Do I make the traits classes global or should I pass them in as a template parameter for class C?

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• Create a subtitle for menu items in Silverstripe CMS?

  - by ELF

  Hi I'm using Silverstripe CMS on the "Simple" template. I'm wondering how to create subtitles for the menu items. The current navigation template is like so: <nav class="primary"> <span class="nav-open-button">²</span> <ul> <% loop $Menu(2) %> <li class="$LinkingMode"><a href="$Link" title="$Title.XML">$MenuTitle.XML</a></li> <% end_loop %> </ul> I'm thinking i could somehow edit $Menutitle.XML but how? Also the sub title should be displayed directly under the Title but as the same button. The SubTitle would need to have a different css rule so that it could be smaller. I know that the CMS has an area for me to edit the page titles which become the menu titles, would it be easy to add a subtitle to the admin like that or is there some other easier way? I only need to make a few of them.

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• STLifying C++ classes

  - by shambulator

  I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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• C++: Trouble with dependent types in templates

  - by Rosarch

  I'm having trouble with templates and dependent types: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> set<result_t> findAll_if(typename set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred) // warning C4346 { set<result_t> result; return findAll_if_rec(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> set<result_t> findAll_if_rec(set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred, set<result_t> result) { typename set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.add(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } Compiler complaints, from the location noted above: warning C4346: 'std::set<result_t>::iterator' : dependent name is not a type. prefix with 'typename' to indicate a type error C2061: syntax error : identifier 'iterator' What am I doing wrong?

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• How to reference {{outlet}} in Ember.CollectionView's itemView

  - by ceed

  I am new to ember and ran into a problem and could not find an answer online. I have a collectionView App.MyView = Ember.CollectionView.extend({ itemViewClass: 'App.MyViewItem', contentBinding: 'controller' }); and the itemViewClass App.MyViewItem = Ember.View.extend({ templateName: 'mytemplate' }); the template looks like that: <div {{action 'select' view.content}}>{{view.content.name}}</div> {{outlet detail}} </div> This produces the content list just fine. In the controller, I have an action: select: function(evt){ this.transitionToRoute('item', evt); } What I want to do is to transition to a nested route when selecting the item (which works fine) and also load more data of the selected item into {{outlet detail}}. While I can load the content of the "item" route into an outlet of e.g. application.hbs, I don't know how to reference the outlet of the selected collectionView item so that the detailed contents are displayed within the existing view. I tried to use: this.render('item', { outlet: 'detail', into: '????' }); within the item Route, but I don't know how to reference the collectionview item template. Maybe there's also a much easier way of loading more data from an item in the item's view (while changing the route at the same time). Any help would be appreciated.

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• XSLT, process elements one by one

  - by qui

  Hi I am quite weak at XSLT so this might seem obvious. Here is some sample XML <term> <name>cholecystocolonic fistula</name> <definition>blah blah</definition> <reference>cholecystocolostomy</reference> </term> And here is the XSLT I wrote a while ago to process it <xsl:template name="term"> { "dictitle": "<xsl:value-of select="name" disable-output-escaping="yes" />", "html": "<xsl:value-of select="definition" disable-output-escaping="yes"/>", "referece": "<xsl:value-of select="reference" disable-output-escaping="yes"/> } </xsl:template> Basically I am creating JSON from the XML. The requirements have now changed so that now the XML can have more than one definition tag and reference tag. They can appear in any order, i.e definition, reference, reference, definition, reference. How can I update the XSLT to accommodate this? Probably worth mentioning that because my XSLT processor is using .NET I can only use XSLT 1.0 commands. Many thanks!

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• C++ STL 101: Overload function causes build error

  - by Sidjal

  Trivial code that works if I do not overload myfunc. void myfunc(int i) { std::cout << "calling myfunc with arg " << i << std::endl; } void myfunc(std::string s) { std::cout << "calling myfunc with arg " << s << std::endl; } void testalgos() { std::vector<int> v; v.push_back(1); v.push_back(2); std::vector<std::string> s; s.push_back("one"); s.push_back("two"); std::for_each( v.begin(), v.end(), myfunc); std::for_each( s.begin(), s.end(), myfunc); return; } int _tmain(int argc, _TCHAR* argv[]) { std::cout << "Hello World" << std::endl; testalgos(); return 0; } The following build errors repeat for both for_each calls. error C2914: 'std::for_each' : cannot deduce template argument as function argument is ambiguous error C2784: '_Fn1 std::for_each(_InIt,_InIt,_Fn1)' : could not deduce template argument for '_InIt' from 'std::_Vector_iterator<_Ty,_Alloc'. It does work if I do not overload myfunc.Can someone explain what is happening here. TIA

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• GetLocalValueEnumerator() Not Returning All Properties

  - by a_hardin

  I am trying to perform validation in my WPF application using the solution in Detecting WPF Validation Errors. public static bool IsValid(DependencyObject parent) { // Validate all the bindings on the parent bool valid = true; LocalValueEnumerator localValues = parent.GetLocalValueEnumerator(); while (localValues.MoveNext()) { LocalValueEntry entry = localValues.Current; if (BindingOperations.IsDataBound(parent, entry.Property)) { Binding binding = BindingOperations.GetBinding(parent, entry.Property); foreach (ValidationRule rule in binding.ValidationRules) { ValidationResult result = rule.Validate(parent.GetValue(entry.Property), null); if (!result.IsValid) { BindingExpression expression = BindingOperations.GetBindingExpression(parent, entry.Property); System.Windows.Controls.Validation.MarkInvalid(expression, new ValidationError(rule, expression, result.ErrorContent, null)); valid = false; } } } } // Validate all the bindings on the children for (int i = 0; i != VisualTreeHelper.GetChildrenCount(parent); ++i) { DependencyObject child = VisualTreeHelper.GetChild(parent, i); if (!IsValid(child)) { valid = false; } } return valid; } The problem I am running into is that when I step through the code for a TextBox, I'm not getting the Text property. The only properties I get are "PageHeight", "Instance", and "UndoManagerInstance". Therefore, I can not Validate the rules for the binding on the TextBox. Does anyone have any idea why I wouldn't be getting the correct properties? Is there another way to force validaton on controls in WPF? I haven't been able to find anyone else who has had this problem. Update: The TextBoxes I am trying to validate are within a DataTemplate. I found that if I copy one of the TextBoxes and place it directly in the Window, I am able to get the data. Using Woodstock, I saw that the data source for the TextBoxes in the template is "ParentTemplate", but it's "Local" for the TextBox outside of the template. So, the question now is, how can I get the DependencyProperties for controls inside a DataTemplate?

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• reverse many to many fields in Django + count them

  - by cleliodpaula

  I'm trying to figure out how to solve this class Item(models.Model): type = models.ForeignKey(Type) name = models.CharField(max_lenght = 10) ... class List(models.Model): items = models.ManyToManyField(Item) ... I want to count how many an Item appears in another Lists, and show on template. view def items_by_list(request, id_): list = List.objects.get(id = id_) qr = list.items.all() #NOT TESTED num = [] i = 0 for item in qr: num[i] = List.objects.filter(items__id = item__id ).count() #FINISH NOT TESTED c = {} c.update(csrf(request)) c = {'request':request, 'list' : qr, 'num' : num} return render_to_response('items_by_list.html', c, context_instance=RequestContext(request)) template {% for dia in list %} <div class="span4" > <div> <h6 style="color: #9937d8">{{item.type.description}}</h6> <small style="color: #b2e300">{{ item.name }}</small> <small style="color: #b2e300">{{COUNT HOW MANY TIMES THE ITEM APPEAR ON OTHER LISTS}}</small> </div> {% endfor %} This seems to be easy, but I could not implement yet. If anyone has some glue to me, please help me. Thanks in advance.

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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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• Replacing text with variables

  - by Steve

  I have to send out letters to certain clients and I have a standard letter that I need to use. I want to replace some of the text inside the body of the message with variables. Here is my maturity_letter models.py class MaturityLetter(models.Model): default = models.BooleanField(default=False, blank=True) body = models.TextField(blank=True) footer = models.TextField(blank=True) Now the body has a value of this: Dear [primary-firstname], AN IMPORTANT REMINDER… You have a [product] that is maturing on [maturity_date] with [financial institution]. etc Now I would like to replace everything in brackets with my template variables. This is what I have in my views.py so far: context = {} if request.POST: start_form = MaturityLetterSetupForm(request.POST) if start_form.is_valid(): agent = request.session['agent'] start_date = start_form.cleaned_data['start_date'] end_date = start_form.cleaned_data['end_date'] investments = Investment.objects.all().filter(maturity_date__range=(start_date, end_date), plan__profile__agent=agent).order_by('maturity_date') inv_form = MaturityLetterInvestments(investments, request.POST) if inv_form.is_valid(): sel_inv = inv_form.cleaned_data['investments'] context['sel_inv'] = sel_inv maturity_letter = MaturityLetter.objects.get(id=1) context['mat_letter'] = maturity_letter context['inv_form'] = inv_form context['agent'] = agent context['show_report'] = True Now if I loop through the sel_inv I get access to sel_inv.maturity_date, etc but I am lost in how to replace the text. On my template, all I have so far is: {% if show_letter %} {{ mat_letter.body }} <br/> {{ mat_letter.footer }} {% endif %} Much appreciated.

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• Can I use a UINavigationController as the detail view of a UISplitViewController?

  - by B Sweigard

  I'm running into a problem with an iPad app where I would like to have UINavigationControllers in both of the views within a UISplitView. I've looked through other similar questions here, but most link to a tutorial online that doesn't completely solve the problem. Here's a 2-minute walkthrough to re-create the problem I'm having: Create a New Project in XCode, starting from the Split View-based Application template. Add the following NSLog statement as the first line within the DetailViewController's willHideViewController method: NSLog(@"toolbar: %@", toolbar); If you run the application now, the log will show that the DetailViewController's toolbar is alive and well. Now... Open MainWindow.xib and expand the SplitViewController. Drag a Navigation Controller from the library on top of the DetailViewController. Expand the new Navigation Controller and change the class of the UIViewController within to a DetailViewController. Ctrl-drag from the SplitViewController to the DetailViewController and assign it as the delegate. Save MainWindow.xib and run the app again. At this point, the detail view has a navigation bar and an empty toolbar. If you view the logs, you should find that the toolbar is null. Why is this? Am I missing some sort of connection in Interface Builder? Is the navigation bar the problem for some reason? Unlike the tutorial at http://www.cimgf.com/2010/05/24/fixing-the-uisplitviewcontroller-template/, I would like to keep both the navigation bar and the toolbar (preferably with the toolbar at the top when in portrait and not visible when in landscape), so that I still have a functional "Back" button when the iPad is in portrait orientation. Does anyone have any suggestions for fixing this problem? An example project with this sort of set-up would be ideal.

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• Is there any trick to match two XML by one XSLT?

  - by brain_pusher

  Is there any trick to match two XML by one XSLT? I mean the way I can apply XSLT to a parameter passed. For example (I missed declarations to be short). XML1: XML to be transformed: <myData> <Collection> </Collection> </myData> XSLT need to be applied to the previous XML: <xsl:param name='items' /> <xsl:template match='Collection'> <!-- some transformation here --> </xsl:template> XML2: XML data passed as the parameter 'items': <newData> <Item>1</Item> <Item>2</Item> <Item>3</Item> </newData> And I need to create a set of nodes in the 'Collection' node in XML1 for each 'Item' element in XML2 using XSLT. And I do not know what XML2 contains exactly at design time. It is generated at runtime, so I can't place it inside XSLT, I know only its schema.

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• How to process more that one XML document in XSLT?

  - by brain_pusher

  Is there any trick to match two XML by one XSLT? I mean the way I can apply XSLT to a parameter passed. For example (I missed declarations to be short). XML1: XML to be transformed: <myData> <Collection> </Collection> </myData> XSLT need to be applied to the previous XML: <xsl:param name='items' /> <xsl:template match='Collection'> <!-- some transformation here --> </xsl:template> XML2: XML data passed as the parameter 'items': <newData> <Item>1</Item> <Item>2</Item> <Item>3</Item> </newData> And I need to create a set of nodes in the 'Collection' node in XML1 for each 'Item' element in XML2 using XSLT. And I do not know what XML2 contains exactly at design time. It is generated at runtime, so I can't place it inside XSLT, I know only its schema.

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• for loop vs std::for_each with lambda

  - by Andrey

  Let's consider a template function written in C++11 which iterates over a container. Please exclude from consideration the range loop syntax because it is not yet supported by the compiler I'm working with. template <typename Container> void DoSomething(const Container& i_container) { // Option #1 for (auto it = std::begin(i_container); it != std::end(i_container); ++it) { // do something with *it } // Option #2 std::for_each(std::begin(i_container), std::end(i_container), [] (typename Container::const_reference element) { // do something with element }); } What are pros/cons of for loop vs std::for_each in terms of: a) performance? (I don't expect any difference) b) readability and maintainability? Here I see many disadvantages of for_each. It wouldn't accept a c-style array while the loop would. The declaration of the lambda formal parameter is so verbose, not possible to use auto there. It is not possible to break out of for_each. In pre- C++11 days arguments against for were a need of specifying the type for the iterator (doesn't hold any more) and an easy possibility of mistyping the loop condition (I've never done such mistake in 10 years). As a conclusion, my thoughts about for_each contradict the common opinion. What am I missing here?

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• insertvalue function in stack class is not calling when pointing by smartpointer class? please expai

  - by user323422

  template< class Type > class cStack { Type *m_array; int m_Top; int m_Size; public:cStack(); cStack(const Type&); cStack(const cStack<Type> &); bool Is_Full(); bool Is_Empty(); void InsertValue(const Type&); void RemeoveValue(); ~cStack(); }; template< class Type > class Smartpointer { cStack<Type> *sPtr; public: Smartpointer(); Smartpointer(const Type&); Type* operator->(); Type& operator*(); }; int main() { Smartpointer<int> sptr(1); sptr->InsertValue(2);//its not calling insertvalue } }

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• Checking if a function has C-linkage at compile-time [unsolvable]

  - by scjohnno

  Is there any way to check if a given function is declared with C-linkage (that is, with extern "C") at compile-time? I am developing a plugin system. Each plugin can supply factory functions to the plugin-loading code. However, this has to be done via name (and subsequent use of GetProcAddress or dlsym). This requires that the functions be declared with C-linkage so as to prevent name-mangling. It would be nice to be able to throw a compiler error if the referred-to function is declared with C++-linkage (as opposed to finding out at runtime when a function with that name does not exist). Here's a simplified example of what I mean: extern "C" void my_func() { } void my_other_func() { } // Replace this struct with one that actually works template<typename T> struct is_c_linkage { static const bool value = true; }; template<typename T> void assertCLinkage(T *func) { static_assert(is_c_linkage<T>::value, "Supplied function does not have C-linkage"); } int main() { assertCLinkage(my_func); // Should compile assertCLinkage(my_other_func); // Should NOT compile } Is there a possible implementation of is_c_linkage that would throw a compiler error for the second function, but not the first? I'm not sure that it's possible (though it may exist as a compiler extension, which I'd still like to know of). Thanks.

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• Elegant ways to print out a bunch of instance attributes in python 2.6?

  - by wds

  First some background. I'm parsing a simple file format, and wish to re-use the results in python code later, so I made a very simple class hierarchy and wrote the parser to construct objects from the original records in the text files I'm working from. At the same time I'd like to load the data into a legacy database, the loader files for which take a simple tab-separated format. The most straightforward way would be to just do something like: print "%s\t%s\t....".format(record.id, record.attr1, len(record.attr1), ...) Because there are so many columns to print out though, I thought I'd use the Template class to make it a bit easier to see what's what, i.e.: templ = Template("$id\t$attr1\t$attr1_len\t...") And I figured I could just use the record in place of the map used by a substitute call, with some additional keywords for derived values: print templ.substitute(record, attr1_len=len(record.attr1), ...) Unfortunately this fails, complaining that the record instance does not have an attribute __getitem__. So my question is twofold: do I need to implement __getitem__ and if so how? is there a more elegant way for something like this where you just need to output a bunch of attributes you already know the name for?

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• Announcing the Release of Visual Studio 2013 and Great Improvements to ASP.NET and Entity Framework

  - by ScottGu

  Today we released VS 2013 and .NET 4.5.1. These releases include a ton of great improvements, and include some fantastic enhancements to ASP.NET and the Entity Framework.  You can download and start using them now. Below are details on a few of the great ASP.NET, Web Development, and Entity Framework improvements you can take advantage of with this release.  Please visit http://www.asp.net/vnext for additional release notes, documentation, and tutorials. One ASP.NET With the release of Visual Studio 2013, we have taken a step towards unifying the experience of using the different ASP.NET sub-frameworks (Web Forms, MVC, Web API, SignalR, etc), and you can now easily mix and match the different ASP.NET technologies you want to use within a single application. When you do a File-New Project with VS 2013 you’ll now see a single ASP.NET Project option: Selecting this project will bring up an additional dialog that allows you to start with a base project template, and then optionally add/remove the technologies you want to use in it.  For example, you could start with a Web Forms template and add Web API or Web Forms support for it, or create a MVC project and also enable Web Forms pages within it: This makes it easy for you to use any ASP.NET technology you want within your apps, and take advantage of any feature across the entire ASP.NET technology span. Richer Authentication Support The new “One ASP.NET” project dialog also includes a new Change Authentication button that, when pushed, enables you to easily change the authentication approach used by your applications – and makes it much easier to build secure applications that enable SSO from a variety of identity providers.  For example, when you start with the ASP.NET Web Forms or MVC templates you can easily add any of the following authentication options to the application: No Authentication Individual User Accounts (Single Sign-On support with FaceBook, Twitter, Google, and Microsoft ID – or Forms Auth with ASP.NET Membership) Organizational Accounts (Single Sign-On support with Windows Azure Active Directory ) Windows Authentication (Active Directory in an intranet application) The Windows Azure Active Directory support is particularly cool.  Last month we updated Windows Azure Active Directory so that developers can now easily create any number of Directories using it (for free and deployed within seconds).  It now takes only a few moments to enable single-sign-on support within your ASP.NET applications against these Windows Azure Active Directories.  Simply choose the “Organizational Accounts” radio button within the Change Authentication dialog and enter the name of your Windows Azure Active Directory to do this: This will automatically configure your ASP.NET application to use Windows Azure Active Directory and register the application with it.  Now when you run the app your users can easily and securely sign-in using their Active Directory credentials within it – regardless of where the application is hosted on the Internet. For more information about the new process for creating web projects, see Creating ASP.NET Web Projects in Visual Studio 2013. Responsive Project Templates with Bootstrap The new default project templates for ASP.NET Web Forms, MVC, Web API and SPA are built using Bootstrap. Bootstrap is an open source CSS framework that helps you build responsive websites which look great on different form factors such as mobile phones, tables and desktops. For example in a browser window the home page created by the MVC template looks like the following: When you resize the browser to a narrow window to see how it would like on a phone, you can notice how the contents gracefully wrap around and the horizontal top menu turns into an icon: When you click the menu-icon above it expands into a vertical menu – which enables a good navigation experience for small screen real-estate devices: We think Bootstrap will enable developers to build web applications that work even better on phones, tablets and other mobile devices – and enable you to easily build applications that can leverage the rich ecosystem of Bootstrap CSS templates already out there.  You can learn more about Bootstrap here. Visual Studio Web Tooling Improvements Visual Studio 2013 includes a new, much richer, HTML editor for Razor files and HTML files in web applications. The new HTML editor provides a single unified schema based on HTML5. It has automatic brace completion, jQuery UI and AngularJS attribute IntelliSense, attribute IntelliSense Grouping, and other great improvements. For example, typing “ng-“ on an HTML element will show the intellisense for AngularJS: This support for AngularJS, Knockout.js, Handlebars and other SPA technologies in this release of ASP.NET and VS 2013 makes it even easier to build rich client web applications: The screen shot below demonstrates how the HTML editor can also now inspect your page at design-time to determine all of the CSS classes that are available. In this case, the auto-completion list contains classes from Bootstrap’s CSS file. No more guessing at which Bootstrap element names you need to use: Visual Studio 2013 also comes with built-in support for both CoffeeScript and LESS editing support. The LESS editor comes with all the cool features from the CSS editor and has specific Intellisense for variables and mixins across all the LESS documents in the @import chain. Browser Link – SignalR channel between browser and Visual Studio The new Browser Link feature in VS 2013 lets you run your app within multiple browsers on your dev machine, connect them to Visual Studio, and simultaneously refresh all of them just by clicking a button in the toolbar. You can connect multiple browsers (including IE, FireFox, Chrome) to your development site, including mobile emulators, and click refresh to refresh all the browsers all at the same time.  This makes it much easier to easily develop/test against multiple browsers in parallel. Browser Link also exposes an API to enable developers to write Browser Link extensions.  By enabling developers to take advantage of the Browser Link API, it becomes possible to create very advanced scenarios that crosses boundaries between Visual Studio and any browser that’s connected to it. Web Essentials takes advantage of the API to create an integrated experience between Visual Studio and the browser’s developer tools, remote controlling mobile emulators and a lot more. You will see us take advantage of this support even more to enable really cool scenarios going forward. ASP.NET Scaffolding ASP.NET Scaffolding is a new code generation framework for ASP.NET Web applications. It makes it easy to add boilerplate code to your project that interacts with a data model. In previous versions of Visual Studio, scaffolding was limited to ASP.NET MVC projects. With Visual Studio 2013, you can now use scaffolding for any ASP.NET project, including Web Forms. When using scaffolding, we ensure that all required dependencies are automatically installed for you in the project. For example, if you start with an ASP.NET Web Forms project and then use scaffolding to add a Web API Controller, the required NuGet packages and references to enable Web API are added to your project automatically.  To do this, just choose the Add->New Scaffold Item context menu: Support for scaffolding async controllers uses the new async features from Entity Framework 6. ASP.NET Identity ASP.NET Identity is a new membership system for ASP.NET applications that we are introducing with this release. ASP.NET Identity makes it easy to integrate user-specific profile data with application data. ASP.NET Identity also allows you to choose the persistence model for user profiles in your application. You can store the data in a SQL Server database or another data store, including NoSQL data stores such as Windows Azure Storage Tables. ASP.NET Identity also supports Claims-based authentication, where the user’s identity is represented as a set of claims from a trusted issuer. Users can login by creating an account on the website using username and password, or they can login using social identity providers (such as Microsoft Account, Twitter, Facebook, Google) or using organizational accounts through Windows Azure Active Directory or Active Directory Federation Services (ADFS). To learn more about how to use ASP.NET Identity visit http://www.asp.net/identity.  ASP.NET Web API 2 ASP.NET Web API 2 has a bunch of great improvements including: Attribute routing ASP.NET Web API now supports attribute routing, thanks to a contribution by Tim McCall, the author of http://attributerouting.net. With attribute routing you can specify your Web API routes by annotating your actions and controllers like this: OAuth 2.0 support The Web API and Single Page Application project templates now support authorization using OAuth 2.0. OAuth 2.0 is a framework for authorizing client access to protected resources. It works for a variety of clients including browsers and mobile devices. OData Improvements ASP.NET Web API also now provides support for OData endpoints and enables support for both ATOM and JSON-light formats. With OData you get support for rich query semantics, paging, $metadata, CRUD operations, and custom actions over any data source. Below are some of the specific enhancements in ASP.NET Web API 2 OData. Support for $select, $expand, $batch, and $value Improved extensibility Type-less support Reuse an existing model OWIN Integration ASP.NET Web API now fully supports OWIN and can be run on any OWIN capable host. With OWIN integration, you can self-host Web API in your own process alongside other OWIN middleware, such as SignalR. For more information, see Use OWIN to Self-Host ASP.NET Web API. More Web API Improvements In addition to the features above there have been a host of other features in ASP.NET Web API, including CORS support Authentication Filters Filter Overrides Improved Unit Testability Portable ASP.NET Web API Client To learn more go to http://www.asp.net/web-api/ ASP.NET SignalR 2 ASP.NET SignalR is library for ASP.NET developers that dramatically simplifies the process of adding real-time web functionality to your applications. Real-time web functionality is the ability to have server-side code push content to connected clients instantly as it becomes available. SignalR 2.0 introduces a ton of great improvements. We’ve added support for Cross-Origin Resource Sharing (CORS) to SignalR 2.0. iOS and Android support for SignalR have also been added using the MonoTouch and MonoDroid components from the Xamarin library (for more information on how to use these additions, see the article Using Xamarin Components from the SignalR wiki). We’ve also added support for the Portable .NET Client in SignalR 2.0 and created a new self-hosting package. This change makes the setup process for SignalR much more consistent between web-hosted and self-hosted SignalR applications. To learn more go to http://www.asp.net/signalr. ASP.NET MVC 5 The ASP.NET MVC project templates integrate seamlessly with the new One ASP.NET experience and enable you to integrate all of the above ASP.NET Web API, SignalR and Identity improvements. You can also customize your MVC project and configure authentication using the One ASP.NET project creation wizard. The MVC templates have also been updated to use ASP.NET Identity and Bootstrap as well. An introductory tutorial to ASP.NET MVC 5 can be found at Getting Started with ASP.NET MVC 5. This release of ASP.NET MVC also supports several nice new MVC-specific features including: Authentication filters: These filters allow you to specify authentication logic per-action, per-controller or globally for all controllers. Attribute Routing: Attribute Routing allows you to define your routes on actions or controllers. To learn more go to http://www.asp.net/mvc Entity Framework 6 Improvements Visual Studio 2013 ships with Entity Framework 6, which bring a lot of great new features to the data access space: Async and Task<T> Support EF6’s new Async Query and Save support enables you to perform asynchronous data access and take advantage of the Task<T> support introduced in .NET 4.5 within data access scenarios.  This allows you to free up threads that might otherwise by blocked on data access requests, and enable them to be used to process other requests whilst you wait for the database engine to process operations. When the database server responds the thread will be re-queued within your ASP.NET application and execution will continue.  This enables you to easily write significantly more scalable server code. Here is an example ASP.NET WebAPI action that makes use of the new EF6 async query methods: Interception and Logging Interception and SQL logging allows you to view – or even change – every command that is sent to the database by Entity Framework. This includes a simple, human readable log – which is great for debugging – as well as some lower level building blocks that give you access to the command and results. Here is an example of wiring up the simple log to Debug in the constructor of an MVC controller: Custom Code-First Conventions The new Custom Code-First Conventions enable bulk configuration of a Code First model – reducing the amount of code you need to write and maintain. Conventions are great when your domain classes don’t match the Code First conventions. For example, the following convention configures all properties that are called ‘Key’ to be the primary key of the entity they belong to. This is different than the default Code First convention that expects Id or <type name>Id. Connection Resiliency The new Connection Resiliency feature in EF6 enables you to register an execution strategy to handle – and potentially retry – failed database operations. This is especially useful when deploying to cloud environments where dropped connections become more common as you traverse load balancers and distributed networks. EF6 includes a built-in execution strategy for SQL Azure that knows about retryable exception types and has some sensible – but overridable – defaults for the number of retries and time between retries when errors occur. Registering it is simple using the new Code-Based Configuration support: These are just some of the new features in EF6. You can visit the release notes section of the Entity Framework site for a complete list of new features. Microsoft OWIN Components Open Web Interface for .NET (OWIN) defines an open abstraction between .NET web servers and web applications, and the ASP.NET “Katana” project brings this abstraction to ASP.NET. OWIN decouples the web application from the server, making web applications host-agnostic. For example, you can host an OWIN-based web application in IIS or self-host it in a custom process. For more information about OWIN and Katana, see What's new in OWIN and Katana. Summary Today’s Visual Studio 2013, ASP.NET and Entity Framework release delivers some fantastic new features that streamline your web development lifecycle. These feature span from server framework to data access to tooling to client-side HTML development.  They also integrate some great open-source technology and contributions from our developer community. Download and start using them today! 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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