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  • Class templating std::set key types

    - by TomFLuff
    I have a class to evaluate set algebra but wish to template it. At the minute it looks a bit like this set.h: template<typename T> class SetEvaluation { public: SetEvaluation<T>(); std::set<T> evaluate(std::string in_expression); } set.cpp template<typename T> std::set<T> SetEvaluation<T>::evaluate(std::string expression) { std::set<T> result; etc etc... } But i'm getting undefined reference errors when compiling. Is it possible to declare the return type as std::set<T> and then pass std::string as the class template param. There are no errors in the class but only when I try to instantiate SetEvaluation<std::string> Can anyone shed light on this problem? thanks

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  • Template specialization to use default type if class member typedef does not exist

    - by Frank
    Hi Everyone, I'm trying to write code that uses a member typedef of a template argument, but want to supply a default type if the template argument does not have that typedef. A simplified example I've tried is this: struct DefaultType { DefaultType() { printf("Default "); } }; struct NonDefaultType { NonDefaultType() { printf("NonDefault "); } }; struct A {}; struct B { typedef NonDefaultType Type; }; template<typename T, typename Enable = void> struct Get_Type { typedef DefaultType Type; }; template<typename T> struct Get_Type< T, typename T::Type > { typedef typename T::Type Type; }; int main() { Get_Type::Type test1; Get_Type::Type test2; } I would expect this to print "Default NonDefault", but instead it prints "Default Default". My expectation is that the second line in main() should match the specialized version of Get_Type, because B::Type exists. However, this does not happen. Can anyone explain what's going on here and how to fix it, or another way to accomplish the same goal? Thank you.

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  • Is it possible to supply template parameters when calling operator()?

    - by Paul
    I'd like to use a template operator() but am not sure if it's possible. Here is a simple test case that won't compile. Is there something wrong with my syntax, or is this simply not possible? struct A { template<typename T> void f() { } template<typename T> void operator()() { } }; int main() { A a; a.f<int>(); // This compiles. a.operator()<int>(); // This compiles. a<int>(); // This won't compile. return 0; }

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  • templated class : accessing derived normal-class methods

    - by user1019129
    I have something like this : class Container1 { public: method1() { ... } } class Container2 { public: method1() { ... } } template<class C = Container1> class X : public C { public: using C::method1(); ..... X(string& str) : C(str) {}; X& other_method() { method1(); ...; } } My question is why I have to use "using C::method1()", to be able to access the method.. Most of answers I found is for the case where templated-class inhering templated-class. Normally they mention using "this-", but this does not seem to work in this case. Can I do something else shorter... Also I'm suspecting the other error I'm getting is related to the same problem : no match call for (X<Container1>) (<std::string&>)

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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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  • class T in c++ (your definition)

    - by JohnWong
    The one advantage of using class T in c++ is to reduce the time to redefine data types in a function, if those data types are defined in other function, for example, in int main. template <class T> void showabs(T number) { if (number < 0 ) number = -number; cout << number << endl; return 0; } int main() { int num1 = -4; float num2 = -4.23f; showabs(num1); showabs(num2); return 0; } So in this case, without class T, for each data type, we have to add its corresponding data-type condition, that is, another set of if statement for int, and another one for float. Am I correct?

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  • C++ Template Classes and Copy Construction

    - by themoondothshine
    Is there any way I can construct an new object from the given object if the template parameters of both objects are identical at run-time? For example: I have a template class with the declaration: template<typename _Type1, typename _Type2> class Object; Next, I have two instantiations of the template: template class Object<char, int>; template class Object<wchar_t, wint_t>; Now, I want to write a member function such as: template<typename _Type1, typename _Type2> Object<char, int> Object<_Type1, _Type2>::toCharObject() { if(__gnu_cxx::__are_same<_Type1, char>::__value) return *this; else { //Perform some kind of conversion and return an Object<char, int> } } I have tried a couple of techniques, such as using __gnu_cxx::__enable_if<__gnu_cxx::__are_same<_Type1, char>::__value, _Type1>::__type in a copy constructor for the Oject class, but I keep running into the error: error: conversion from ‘Object<wchar_t, wint_t>’ to non-scalar type ‘Object<char, int>’ requested Is there no way I can do this? Any help will be greatly appreciated!

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  • C++ template + typedef

    - by MMS
    What is wrong in the following code: Point2D.h template <class T> class Point2D { private: T x; T y; ... }; PointsList.h template <class T> class Point2D; template <class T> struct TPointsList { typedef std::vector <Point2D <T> > Type; }; template <class T> class PointsList { private: TPointsList <T>::Type points; //Compiler error ... }; I would like to create new user type TPointsList without direct type specification...

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  • How to loop X times in Django?

    - by Mark
    I have user reviews on my site. Each review has a rating of 1-5 stars. I want to print that many stars. How do I do it? I only see {% for X in Y %} which lets you iterate over a list, but not a certain number of times.

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  • Django: Is it possible to attach media files (css, javascript etc) to a View-class?

    - by mrmclovin
    I can't fins any information on how to define css or javascript files in a view like: class MyView(View): .... class Media: css = { 'all' : 'mystyle.css' } If you have a form you can do like: class MyForm(ModelForm): .... class Media: css = { 'all' : 'mystyle.css' } And then in the template you can print the files like; {{ form.media.css }} I like that Syntax very much and I like to keep the View-specific css files in the app-directory. Does anyone know if it's possible? Thanks!

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  • Will the template argument's destructor to a templated class be called on deletion?

    - by Mutmansky
    If you have a templated base class as in the following example: class A{ A(); virtual ~A(); }; template <class T> class B : public T { B(); virtual ~B(); }; typedef B<A> C; class D : public C { D(); virtual ~D(); }; When you delete an instance of D, will the destructor of A be called? I'll probably create a test program to find out what happens, but just thinking about it, I wasn't sure what should happen.

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  • Template function overloading with identical signatures, why does this work?

    - by user1843978
    Minimal program: #include <stdio.h> #include <type_traits> template<typename S, typename T> int foo(typename T::type s) { return 1; } template<typename S, typename T> int foo(S s) { return 2; } int main(int argc, char* argv[]) { int x = 3; printf("%d\n", foo<int, std::enable_if<true, int>>(x)); return 0; } output: 1 Why doesn't this give a compile error? When the template code is generated, wouldn't the functions int foo(typename T::type search) and int foo(S& search) have the same signature? If you change the template function signatures a little bit, it still works (as I would expect given the example above): template<typename S, typename T> void foo(typename T::type s) { printf("a\n"); } template<typename S, typename T> void foo(S s) { printf("b\n"); } Yet this doesn't and yet the only difference is that one has an int signature and the other is defined by the first template parameter. template<typename T> void foo(typename T::type s) { printf("a\n"); } template<typename T> void foo(int s) { printf("b\n"); } I'm using code similar to this for a project I'm working on and I'm afraid that there's a subtly to the language that I'm not understanding that will cause some undefined behavior in certain cases. I should also mention that it does compile on both Clang and in VS11 so I don't think it's just a compiler bug.

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  • error - inherited class field undeclared according to g++

    - by infoholic_anonymous
    I have a code that has the following logic. g++ gives me the error that I have not declared n in my iterator2. What could be wrong? template <typename T> class List{ template <typename TT> class Node; Node<T> *head; /* (...) */ template <bool D> class iterator1{ protected: Node<T> n; public: iterator1( Node<T> *nn ) { n = nn } /* (...) */ }; template <bool D> class iterator2 : public iterator1<D>{ public: iterator2( Node<T> *nn ) : iterator1<D>( nn ) {} void fun( Node<T> *nn ) { n = nn; } /* (...) */ }; }; EDIT : I attach the actual header file. iterator1 would be iterable_frame and iterator2 - switchable_frame. #ifndef LST_H #define LST_H template <typename T> class List { public: template <typename TT> class Node; private: Node<T> *head; public: List() { head = new Node<T>; } ~List() { empty_list(); delete head; } List( const List &l ); inline bool is_empty() const { return head->next[0] == head; } void empty_list(); template <bool DIM> class iterable_frame { protected: Node<T> *head; Node<T> **caret; public: iterable_frame( const List &l ) { head = *(caret = &l.head); } iterable_frame( const iterable_frame &i ) { head = *(caret = i.caret); } ~iterable_frame() {} /* (...) - a few methods follow */ template <bool _DIM> friend class supervised_frame; }; template <bool DIM> class switchable_frame : public iterable_frame<DIM> { Node<T> *main_head; public: switchable_frame( const List& l ) : iterable_frame<DIM>(l) { main_head = head; } inline bool next_frame() { caret = &head->next[!DIM]; head = *caret; return head != main_head; } }; template <bool DIM> class supervised_frame { iterable_frame<DIM> sentinels; iterable_frame<DIM> cells; public: supervised_frame( const List &l ) : sentinels(l), cells(l) {} ~supervised_frame() {} /* (...) - a few methods follow */ }; template <typename TT> class Node { unsigned index[2]; TT num; Node<TT> *next[2]; public: Node( unsigned x = 0, unsigned y = 0 ) { index[0]=x; index[1]=y; next[0] = this; next[1] = this; } Node( unsigned x, unsigned y, TT d ) { index[0]=x; index[1]=y; num=d; next[0] = this; next[1] = this; } Node( const Node &n ) { index[0] = n.index[0]; index[1] = n.index[1]; num = n.num; next[0] = next[1] = this; } ~Node() {} friend class List; }; }; #include "List.cpp" #endif the exact error log is the following: In file included from main.cpp:1: List.h: In member function ‘bool List<T>::switchable_frame<DIM>::next_frame()’: List.h:77: error: ‘caret’ was not declared in this scope

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  • C++ "delayed" template argument

    - by aaa
    hello. Is there direct way to do the following: template < class > struct f {}; template < class F > void function() { F<int>(); //for example // ? F template <int>(); } function < f >(); I have workaround by using extra class around template struct. I am wondering if it's possible to do so directly. Thanks

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  • C++ require that one template type is derived from the other

    - by Will
    In a comparison operator: template<class R1, class R2> bool operator==(Manager<R1> m1, Manager<R2> m2) { return p1.internal_field == p2.internal_field; } Is there any way I could enforce that R1 and R2 must have a supertype or subtype relation? That is, I'd like to allow either R1 to be derived from R2, or R2 to be derived from R1, but disallow the comparison if R1 and R2 are unrelated types.

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  • How can data templates in generic.xaml get applied automatically?

    - by Thiado de Arruda
    I have a custom control that has a ContentPresenter that will have an arbitrary object set as it content. This object does not have any constraint on its type, so I want this control to display its content based on any data templates defined by application or by data templates defined in Generic.xaml. If in a application I define some data template(without a key because I want it to be applied automatically to objects of that type) and I use the custom control bound to an object of that type, the data template gets applied automatically. But I have some data templates defined for some types in the generic.xaml where I define the custom control style, and these templates are not getting applied automatically. Here is the generic.xaml : If I set an object of type 'PredefinedType' as the content in the contentpresenter, the data template does not get applied. However, If it works if I define the data template in the app.xaml for the application thats using the custom control. Does someone got a clue? I really cant assume that the user of the control will define this data template, so I need some way to tie it up with the custom control.

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  • How do I access session data in Jinja2 templates (Bottle framework on app engine)?

    - by TylerW
    Hello! I'm running the micro framework Bottle on Google App Engine. I'm using Jinja2 for my templates. And I'm using Beaker to handle the sessions. I'm still a pretty big Python newbie and am pretty stoked I got this far :) My question is how do I access the session data within the templates? I can get the session data no problem within the actual python code. And I could pass the session data each time I call a jinja template. But since I need the session data in the main menu bar of the site... that means I would have to pass it on every single page. Does anyone know if I can access it directly in the templates? For example I need the session data for my header links: Home | FAQ | Login or Home | FAQ | Logout Any help is greatly appreciated! :D

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  • How do I use theme preprocessor functions for my own templates?

    - by Jergason
    I have several .tpl.php files for nodes, CCK fields, and Views theming. These template files have a lot of logic in them to move things around, strip links, create new links, etc. I understand that this is bad development and not "The Drupal Way". If I understand correctly, "The Drupal Way" is to use preprocessor functions in your template.php file to manipulate variables and add new variables. A few questions about that: Is there a naming convention for creating a preprocessor function for a specific theme? For example, if I have a CCK field template called content-field-field_transmission_make_model.tpl, how would I name the preprocessor function? Can I use template preprocessor functions for node templates, CCK field templates, and Views templates? Do they have different methods of modifying template variables or adding new ones?

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  • Sales and Procurement Contracts 12.1.3++ Release Information

    - by LuciaC
    New functionality has been released for Sales and Procurement Contracts in a new patch: Contracts 12.1.3++: Patch 13877401: 12.1.3 Rollup for Oracle Contracts Core. The new functionality includes: APIs for Import of Contract Templates, Contract Expert rules, Questions and Constants: The three APIs are as follows: API for Templates, API for Rules, and API for Questions and Constants. These can be used to both create entities and update existing templates and rules. The APIs will display error and warning messages which can be processed and analyzed by the customer. Ability to Apply Multiple Templates to a Sourcing, Procurement or Sales Document: The buyer can select and add multiple templates to a quote,sales agreement document, sourcing or purchasing odcument.  All the clauses and deliverables from the new templates are synchronized with the document. The Contract Expert rules are from the original template. The buyer can also view the list of templates that are added to any sales or procurement document. Ability to Define Multi-Row Variables: You can create user defined manual variables that are tables containing one row per line or multiple rows. Contract Preview will print the variable values according to the layout defined for the variable. These variables are not available for Contract Expert Rules and Supplier. Enhancement to Suggested Sections for Clauses by Contract Expert: You can associate multiple default sections with a clause. A clause is associated with multiple values of any system variable and for each such value a section name is associated in Contracts Terms Library. When Contract Expert is run in the contract authoring flow, the clause is automatically placed in the associated section name. Plus many more new features. Read the following notes for details on all the new and changed functionality: Oracle Procurement Contracts Release Notes, Release 12.1.3++ (Doc ID 1467140.1) Oracle Sales Contracts Release Notes, Release 12.1.3++ (Doc ID 1467149.1) Oracle E-Business Suite Releases 12.1 and 12.2 Release Content Documents (Doc ID 1302189.1)

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