Search Results

Search found 19044 results on 762 pages for 'template language'.

Page 265/762 | < Previous Page | 261 262 263 264 265 266 267 268 269 270 271 272  | Next Page >

  • C++ using typedefs in non-inline functions

    - by ArunSaha
    I have a class like this template< typename T > class vector { public: typedef T & reference; typedef T const & const_reference; typedef size_t size_type; const_reference at( size_t ) const; reference at( size_t ); and later in the same file template< typename T > typename vector<T>::const_reference // Line X vector<T>::at( size_type i ) const { rangecheck(); return elems_[ i ]; } template< typename T > reference // Line Y vector<T>::at( size_type i ) { rangecheck(); return elems_[ i ]; } Line X compiles fine but Line Y does not compile. The error message from g++ (version 4.4.1) is: foo.h:Y: error: expected initializer before 'vector' From this I gather that, if I want to have non-inline functions then I have to fully qualify the typedef name as in Line X. (Note that, there is no problem for size_type.) However, at least to me, Line X looks clumsy. Is there any alternative approach?

    Read the article

  • vb.net sqlite how to loop through selected records and pass each record as a parameter to another fu

    - by mazrabul
    Hi, I have a sqlite table with following fields: Langauge level hours German 2 50 French 3 40 English 1 60 German 1 10 English 2 50 English 3 60 German 1 20 French 2 40 I want to loop through the records based on language and other conditions and then pass the current selected record to a different function. So I have the following mixture of actual code and psudo code. I need help with converting the psudo code to actual code, please. I am finding it difficult to do so. Here is what I have: Private sub mainp() Dim oslcConnection As New SQLite.SQLiteConnection Dim oslcCommand As SQLite.SQLiteCommand Dim langs() As String = {"German", "French", "English"} Dim i as Integer = 0 oslcConnection.ConnectionString = "Data Source=" & My.Settings.dbFullPath & ";" oslcConnection.Open() oslcCommand = oslcConnection.CreateCommand Do While i <= langs.count If langs(i) = "German" Then oslcCommand.CommandText = "SELECT * FROM table WHERE language = '" & langs(i) & "';" For each record selected 'psudo code If level = 1 Then 'psudo code update level to 2 'psudo code minorp(currentRecord) 'psudo code: calling minorp function and passing the whole record as a parameter End If 'psudo code If level = 2 Then 'psudo code update level to 3 'psudo code minorp(currentRecord) 'psudo code: calling minorp function and passing the whole record as a parameter End If 'psudo code Next 'psudo code End If If langs(i) = "French" Then oslcCommand.CommandText = "SELECT * FROM table WHERE language = '" & langs(i) & "';" For each record selected 'psudo code If level = 1 Then 'psudo code update level to 2 'psudo code minorp(currentRecord) 'psudo code: calling minorp function and passing the whole record as a parameter End If 'psudo code If level = 2 Then 'psudo code update level to 3 'psudo code minorp(currentRecord) 'psudo code: calling minorp function and passing the whole record as a parameter End If 'psudo code Next 'psudo code End If Loop End Sub Many thanks for your help.

    Read the article

  • Anyone NOT using a Web Framework? Why?

    - by tom
    I'm well aware of the many reasons to use a web framework. I'm just wondering whether anyone out there is using absolutely no web framework whatsoever to develop their web projects. I would really love to know the reason(s) why you're not using a web framework. For the sake of this discussion, your programming language of choice does not matter. Some possibilities for discussion: You don't hide behind an ORM. You don't rely on any sort of templating system. You think MVC is a really nice TLA but lacks an essential vowel or two. No need for any additional javascript framework tomfoolery. You just write as much code as possible in your native programming language(s). Summary of reasons thus far: Language learning opportunities. Specific performance reasons (write-intensive transaction processing). Seeking more nuanced control over your data and applications (less abstraction). You're building your own framework! Prove to yourself that you can succeed (or fail) just like the big framework-building gurus. Integration issues with unpopular/legacy technologies (exotic databases or protocols come to mind). Big company, lots of code, no talent nor buy-in present to move to a web framework. Some frameworks really lock you in and cannot perpetually grow along with your needs. These few black sheep don't make it easy to jump outside of the framework, write some custom code, and easily jump back in. When you finally escape the asylum, you'll never look back.

    Read the article

  • ASP.Net MVC DotNetOpenAuth Sample Issue on publish

    - by Roger D. Pharr
    I'm trying to use the MSDN Open ID project template for ASP.NET MVC C#. I've been able to configure a local copy to run well. But when I publish it to my hosting provider - it craps out. The error is "500 internal server error". Is there something I should know about publishing this template that I haven't noticed? Here are some more details (for diligence): Hosting provider is GoDaddy/SQL2005/IIS7. When I configure & publish the blank MVC template, it works. The local database publishes successfully, but I haven't been able to troubleshoot the connection in web.config yet. I expect there are connection string problems in the file. I tried disabling all of the references to log4net, as it seemed to be invoked several times on startup. But those changes did not seem to make a difference in either the local or published application performance. My IDE is Visual Studio 2010 Pro Any help would be greatly appreciated!

    Read the article

  • C++ Namespaces & templates question

    - by Kotti
    Hi! I have some functions that can be grouped together, but don't belong to some object / entity and therefore can't be treated as methods. So, basically in this situation I would create a new namespace and put the definitions in a header file, the implementation in cpp file. Also (if needed) I would create an anonymous namespace in that cpp file and put all additional functions that don't have to be exposed / included to my namespace's interface there. See the code below (probably not the best example and could be done better with another program architecture, but I just can't think of a better sample...) Sample code (header) namespace algorithm { void HandleCollision(Object* object1, Object* object2); } Sample code (cpp) #include "header" // Anonymous namespace that wraps // routines that are used inside 'algorithm' methods // but don't have to be exposed namespace { void RefractObject(Object* object1) { // Do something with that object // (...) } } namespace algorithm { void HandleCollision(Object* object1, Object* object2) { if (...) RefractObject(object1); } } So far so good. I guess this is a good way to manage my code, but I don't know what should I do if I have some template-based functions and want to do basically the same. If I'm using templates, I have to put all my code in the header file. Ok, but how should I conceal some implementation details then? Like, I want to hide RefractObject function from my interface, but I can't simply remove it's declaration (just because I have all my code in a header file)... The only approach I came up with was something like: Sample code (header) namespace algorithm { // Is still exposed as a part of interface! namespace impl { template <typename T> void RefractObject(T* object1) { // Do something with that object // (...) } } template <typename T, typename Y> void HandleCollision(T* object1, Y* object2) { impl::RefractObject(object1); // Another stuff } } Any ideas how to make this better in terms of code designing?

    Read the article

  • Different programming languages possibilities

    - by b-gen-jack-o-neill
    Hello. This should be very simple question. There are many programming languages out there, compiled into machine code or managed code. I first started with ASM back in high school. Assembler is very nice, since you know what exactly CPU does. Next, (as you can see from my other questions here) I decided to learn C and C++. I choosed C becouse from what I read it is the language with output most close to assembler-written programs. But, what I want to know is, can any other Windows programming language out there call win32 API? To be exact, like C has its special header and functions for win32 api interactions, is this assumed to be some important part of programming language? Or are there any languages that have no support for calling win32 API, or just use console to IO and some functions for basic file IO? Becouse, for Windows programming with graphic output, it is essential to have acess to win32 API. I know this question might seem silly, but still please, help me, I ask for study porposes. Thanks.

    Read the article

  • writing a meta refresh method for rails

    - by aaronstacy
    I want a method in app/controllers/application.rb that can prepend/append text to whatever template gets rendered. Of course I can't call render twice w/o getting a double render error, so is this possible? I want to redirect after a delay using a meta refresh. Here's what I've got: app/controllers/application_controller.rb: def redirect_after_delay (url, delay) @redirect_delay = delay @redirect_url = url render end app/views/layouts/application.html.erb <!DOCTYPE html> <html lang="en"> <head> <%= yield :refresh_tag %> </head> <body> <%= yield %> </body> </html> So then if I want to add a redirect-after-delay, I add the following to 1) my controller and 2) the action's view: app/controllers/my_controller.rb def my_action redirect_after_delay 'http://www.google.com', 3 if some_condition end app/views/my_controller/my_action.html.erb <% content_for :refresh_tag do %> <meta http-equiv='refresh' content='<%=@redirect_delay%>;url=<%=@redirect_url%>'> <% end %> <h1>Please wait while you are redirected...</h1> Since the content_for block never changes, is it possible to do this in some generic way so that I don't have to put <%= yield :refresh_tag %> in each template? (e.g. could redirect_after_delay add it into whatever template is going to be rendered?)

    Read the article

  • Django - partially validating form

    - by aeter
    I'm new to Django, trying to process some forms. I have this form for entering information (creating a new ad) in one template: class Ad(models.Model): ... category = models.CharField("Category",max_length=30, choices=CATEGORIES) sub_category = models.CharField("Subcategory",max_length=4, choices=SUBCATEGORIES) location = models.CharField("Location",max_length=30, blank=True) title = models.CharField("Title",max_length=50) ... I validate it with "is_valid()" just fine. Basically for the second validation (another template) I want to validate only against "category" and "sub_category": In another template, I want to use 2 fields from the same form ("category" and "sub_category") for filtering information - and now the "is_valid()" method would not work correctly, cause it validates the entire form, and I need to validate only 2 fields. I have tried with the following: ... if request.method == 'POST': # If a filter for data has been submitted: form = AdForm(request.POST) try: form = form.clean() category = form.category sub_category = form.sub_category latest_ads_list = Ad.objects.filter(category=category) except ValidationError: latest_ads_list = Ad.objects.all().order_by('pub_date') else: latest_ads_list = Ad.objects.all().order_by('pub_date') form = AdForm() ... but it doesn't work. How can I validate only the 2 fields category and sub_category?

    Read the article

  • Basic question in XSL regarding preceding text

    - by Rachel
    I am new to XSL and i have a basic question on the context of using preceding text. My template match is on the text node. I am iterating over an xml file and within my for loop i am trying to take the preceding text of the text node. Unfortunately preceding::text() is not working if i use it within a for loop. I want to use it within the for loop but how can do it? <xsl:template match="text()"> <xsl:variable name="this" as="text()" select="."/> <xsl:for-each select="$input[@id = generate-id(current())]"> <xsl:variable name="preText" as="xsd:integer" select="sum(preceding::text()[. >> //*[@id=@name]]/string-length(.))"/> ... ... </xsl:for-each> </xsl:template>

    Read the article

  • Why does the WCF 3.5 REST Starter Kit do this?

    - by Brandon
    I am setting up a REST endpoint that looks like the following: [WebInvoke(Method = "POST", UriTemplate = "?format=json", BodyStyle = WebMessageBodyStyle.WrappedRequest, ResponseFormat = WebMessageFormat.Json)] and [WebInvoke(Method = "DELETE", UriTemplate = "?token={token}&format=json", ResponseFormat = WebMessageFormat.Json)] The above throws the following error: UriTemplateTable does not support '?format=json' and '?token={token}&format=json' since they are not equivalent, but cannot be disambiguated because they have equivalent paths and the same common literal values for the query string. See the documentation for UriTemplateTable for more detail. I am not an expert at WCF, but I would imagine that it should map first by the HTTP Method and then by the URI Template. It appears to be backwards. If both of my URI templates are: ?token={token}&format=json This works because they are equivalent and it then appears to look at the HTTP Method where one is POST and the other is DELETE. Is REST supposed to work this way? Why are the URI Template Tables not being sorted first by HTTP Method and then by URI Template? This can cause some serious frustrations when 1 HTTP Method requires a parameter and another does not, or if I want to do optional parameters (e.g. if the 'format' parameter is not passed, default to XML).

    Read the article

  • C++, generic programming and virtual functions. How do I get what I want?

    - by carleeto
    This is what I would like to do using templates: struct op1 { virtual void Method1() = 0; } ... struct opN { virtual void MethodN() = 0; } struct test : op1, op2, op3, op4 { virtual void Method1(){/*do work1*/}; virtual void Method2(){/*do work2*/}; virtual void Method3(){/*do work3*/}; virtual void Method4(){/*do work4*/}; } I would like to have a class that simply derives from a template class that provides these method declarations while at the same time making them virtual. This is what I've managed to come up with: #include <iostream> template< size_t N > struct ops : ops< N - 1 > { protected: virtual void DoStuff(){ std::cout<<N<<std::endl; }; public: template< size_t i > void Method() { if( i < N ) ops<i>::DoStuff(); } //leaving out compile time asserts for brevity } struct test : ops<6> { }; int main( int argc, char ** argv ) { test obj; obj.Method<3>(); //prints 3 return 0; } However, as you've probably guessed, I am unable to override any of the 6 methods I have inherited. I'm obviously missing something here. What is my error? No, this isn't homework. This is curiosity.

    Read the article

  • c++ specialized overload?

    - by acidzombie24
    -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

    Read the article

  • Why `is_base_of` works with private inheritance?

    - by Alexey Malistov
    Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class B {}; class D : private B {}; //Exspression is true. int test[is_base_of<B,D>::value && !is_base_of<D,B>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

    Read the article

  • How do interpreters written in C and C++ bind identifiers to C(++) functions

    - by sub
    I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do interpreters written in C/C++ solve this problem? How can I solve this for my own experimental toy interpreter written in C++?

    Read the article

  • Initializing static pointer in templated class.

    - by Anthony
    This is difficult for me to formulate in a Google query (at least one that gives me what I'm looking for) so I've had some trouble finding an answer. I'm sure I'm not the first to ask though. Consider a class like so: template < class T > class MyClass { private: static T staticObject; static T * staticPointerObject; }; ... template < class T > T MyClass<T>::staticObject; // <-- works ... template < class T > T * MyClass<T>::staticPointerObject = NULL; // <-- cannot find symbol staticPointerObject. I am having trouble figuring out why I cannot successfully create that pointer object. Edit: The above code is all specified in the header, and the issue I mentioned is an error in the link step, so it is not finding the specific symbol.

    Read the article

  • overloading "<<" with a struct (no class) cout style

    - by monkeyking
    I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

    Read the article

  • clang does not compile but g++ does

    - by user1095108
    Can someone help me with this code: #include <type_traits> #include <vector> struct nonsense { }; template <struct nonsense const* ptr, typename R> typename std::enable_if<!std::is_void<R>::value, int>::type fo(void* const) { return 0; } template <struct nonsense const* ptr, typename R> typename std::enable_if<std::is_void<R>::value, int>::type fo(void* const) { return 1; } typedef int (*func_type)(void*); template <std::size_t O> void run_me() { static struct nonsense data; typedef std::pair<char const* const, func_type> pair_type; std::vector<pair_type> v; v.push_back(pair_type{ "a", fo<&data, int> }); v.push_back(pair_type{ "b", fo<&data, void> }); } int main(int, char*[]) { run_me<2>(); return 0; } clang-3.3 does not compile this code, but g++-4.8.1 does, which of the two compiler is right? Is something wrong with the code, as I suspect? The error reads: a.cpp:32:15: error: no matching constructor for initialization of 'pair_type' (aka 'pair<const char *const, func_type>') v.push_back(pair_type{ "a", fo<&data, int> }); ^ ~~~~~~~~~~~~~~~~~~~~~~~ a.cpp:33:15: error: no matching constructor for initialization of 'pair_type' (aka 'pair<const char *const, func_type>') v.push_back(pair_type{ "b", fo<&data, void> }); ^ ~~~~~~~~~~~~~~~~~~~~~~~~

    Read the article

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

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

    Read the article

  • compact XSLT code to drop N number of tags if all are null.

    - by infant programmer
    This is my input xml: <root> <node1/> <node2/> <node3/> <node4/> <othertags/> </root> The output must be: <root> <othertags/> </root> if any of the 4 nodes isn't null then none of the tags must be dropped. example: <root> <node1/> <node2/> <node3/> <node4>sample_text</node4> <othertags/> </root> Then the output must be same as input xml. <root> <node1/> <node2/> <node3/> <node4>sample_text</node4> <othertags/> </root> This is the XSL code I have designed :: <xsl:template match="@*|node()"> <xsl:copy> <xsl:apply-templates select="@*|node()"/> </xsl:copy> </xsl:template> <xsl:template match="/root/node1[.='' and ../node2/.='' and ../node3/.='' and ../node4/.=''] |/root/node2[.='' and ../node1/.='' and ../node3/.='' and ../node4/.=''] |/root/node3[.='' and ../node1/.='' and ../node2/.='' and ../node4/.=''] |/root/node4[.='' and ../node1/.='' and ../node2/.='' and ../node3/.='']"/> As you can see the code requires more effort and becomes more bulky as the number of nodes increase. Is there any alternative way to overcome this bottleneck?

    Read the article

  • How do C and C++ interpreters bind identifiers to functions

    - by sub
    I'm talking about C and/or C++ here as this are the only languages I know used for interpreters where the following could be a problem: If we have an interpreted language X how can a library written for it add functions to the language which can then be called from within programs written in the language? PHP example: substr( $str, 5, 10 ); How is the function substr added to the "function pool" of PHP so it can be called from within scripts? It is easy for PHP storing all registered function names in an array and searching through it as a function is called in a script. However, as there obviously is no eval in C(++), how can the function then be called? I assume PHP doesn't have 100MB of code like: if( identifier == "substr" ) { return PHP_SUBSTR(...); } else if( ... ) { ... } Ha ha, that would be pretty funny. I hope you have understood my question so far. How do C/C++ interpreters solve this problem? How can I solve this for my own experimental toy interpreter?

    Read the article

  • What are the Limitations for Connecting to an Access Query in Excel

    - by thornomad
    I have an Access 2007 database that has a number of tables, some are fairly large (100,000+ records); I have created a union query to pull some of the same types of data from multiple tables into one large query for pivot table manipulation and reporting. For example: SELECT Language FROM Table1 UNION ALL SELECT Language FROM Table2 UNION ALL SELECT Language FROM Table3; This works. I found, quickly, however, that a union query will not show up when connecting to the datasource from Excel 2007. So, I created a second query to reference the union query. Like so: SELECT * FROM [The Above Union Query]; This query works and it, initially, was accessible from Excel. Time passed, I've added more data. Suddenly, when I connect to my Access database from Excel my query referencing the union has disappeared. MS Access shows no signs of an issue (data displays in Access) and my other non-union queries are showing up in Excel 2007 ... but not the one that references the union. What could be going on? Why did it disappear? I noticed if I switch some of the referenced tables in the union query to a smaller table (with less rows) all of sudden the query appears in Excel again. At least, I think that's what the difference is. I really can't put my finger on why some of the union queries won't show up and some will. Am stumped and need some guidance. Thanks.

    Read the article

  • Best way to build an application based on R?

    - by Prasad Chalasani
    I'm looking for suggestions on how to go about building an application that uses R for analytics, table generation, and plotting. What I have in mind is an application that: displays various data tables in different tabs, somewhat like in Excel, and the columns should be sortable by clicking. takes user input parameters in some dialog windows. displays plots dynamically (i.e. user-input-dependent) either in a tab or in a new pop-up window/frame Note that I am not talking about a general-purpose fron-end/GUI for exploring data with R (like say Rattle), but a specific application. Some questions I'd like to see addressed are: Is an entirely R-based approach even possible ( on Windows ) ? The following passage from the Rattle article in R-Journal intrigues me: It is interesting to note that the first implementation of Rattle actually used Python for implementing the callbacks and R for the statistics, using rpy. The release of RGtk2 allowed the interface el- ements of Rattle to be written directly in R so that Rattle is a fully R-based application If it's better to use another language for the GUI part, which language is best suited for this? I'm looking for a language where it's relatively "painless" to build the GUI, and that also integrates very well with R. From this StackOverflow question How should I do rapid GUI development for R and Octave methods (possibly with Python)? I see that Python + PyQt4 + QtDesigner + RPy2 seems to be the best combo. Is that the consensus ? Anyone have pointers to specific (open source) applications of the type I describe, as examples that I can learn from?

    Read the article

  • Templates, Function Pointers and C++0x

    - by user328543
    One of my personal experiments to understand some of the C++0x features: I'm trying to pass a function pointer to a template function to execute. Eventually the execution is supposed to happen in a different thread. But with all the different types of functions, I can't get the templates to work. #include `<functional`> int foo(void) {return 2;} class bar { public: int operator() (void) {return 4;}; int something(int a) {return a;}; }; template <class C> int func(C&& c) { //typedef typename std::result_of< C() >::type result_type; typedef typename std::conditional< std::is_pointer< C >::value, std::result_of< C() >::type, std::conditional< std::is_object< C >::value, std::result_of< typename C::operator() >::type, void> >::type result_type; result_type result = c(); return result; } int main(int argc, char* argv[]) { // call with a function pointer func(foo); // call with a member function bar b; func(b); // call with a bind expression func(std::bind(&bar::something, b, 42)); // call with a lambda expression func( [](void)->int {return 12;} ); return 0; } The result_of template alone doesn't seem to be able to find the operator() in class bar and the clunky conditional I created doesn't compile. Any ideas? Will I have additional problems with const functions?

    Read the article

  • NVelocity (or Velocity) as a stand-alone formula evaluator

    - by dana
    I am using NVelocity in my application to generate html emails. My application has an event-driven model, where saving and/or updating of objects causes these emails to be sent out. Each event can trigger zero, one or multiple multiple emails. I want to be able to configure which emails get sent out at run-time without having to modify code. I was thinking I could leverage the NVelocity #if() directive to do this. Here is my idea... Step 1) Prior to email sending, the administrator must configure a formula for NVelocity to evaluate. For example: $User.FirstName == "Jack" Step 2) When an object is saved or created, build an NVelocity template in memory based on the input formula. For example: String formula = GetFormulaFromDB(); // $User.FirstName == "Jack" String templ = "#if( " + formula + ") 1 #else 0 #end"; Step 3) Execute the NVelocity engine in memory against the template. Check the results to see if we have to send the email: String result = VelocityMerge(templ); // utility function if( result.Trim() == "1" ) { SendEmail(); } I know this is not exactly what NVelocity was intended to do, but I think it just might work :) One of the benefits of doing things this way is that the same syntax can be used for the formula as is used inside the template. Does anybody have any words of caution or suggestions? Is there a way to execute the #if() directive without jumping through hoops like I have above? Is there a recommended way to validate the formula syntax ahead of time? Thanks.

    Read the article

  • How to write curiously recurring templates with more than 2 layers of inheritance?

    - by Kyle
    All the material I've read on Curiously Recurring Template Pattern seems to one layer of inheritance, ie Base and Derived : Base<Derived>. What if I want to take it one step further? #include <iostream> using std::cout; template<typename LowestDerivedClass> class A { public: LowestDerivedClass& get() { return *static_cast<LowestDerivedClass*>(this); } void print() { cout << "A\n"; } }; template<typename LowestDerivedClass> class B : public A<LowestDerivedClass> { public: void print() { cout << "B\n"; } }; class C : public B<C> { public: void print() { cout << "C\n"; } }; int main() { C c; c.get().print(); // B b; // Intentionally bad syntax, // b.get().print(); // to demonstrate what I'm trying to accomplish return 0; } How can I rewrite this code to compile without errors (and output "C\nB\n")?

    Read the article

< Previous Page | 261 262 263 264 265 266 267 268 269 270 271 272  | Next Page >