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  • Convert templated parameter type to string

    - by wheaties
    I've got a small bit of DRY going on in code I and others have written that I'd like to reduce but I'm failing to figure out how to get it done. This is legacy COM code but it's interfering with the readability. I'd like to do the following: bool queryInterface<class T, class V>(T &_input, V &_output, Logger &_logger){ if( FAILED( _input->QueryInterface( &_output ) ) ){ _logger.error() << "Failed to Query Interface between " << MAGICHAPPENS<T>() << " and " << MAGICHAPPENS<V>(); return false; } if( _output == NULL ){ _logger.warn() << "Unable to Query Interface between " << MAGICHAPPENS<T>() << " and " << MAGICHAPPENS<V>(); return false; } } Wherein the "MAGICHAPPENS()" function would spit out the name of the variable type. Such that if "V" were a IQueryFilter I'd get back a string of "IQueryFilter." I can't think of any reasonable solution without having to write a bunch of template specializations totally defeating the point in the first place. Is there a way to write ANDMAGICHAPPENS?

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  • how to change mod_mainmenu output structure in joomla

    - by Prakash
    how is it possible to change the mod_mainmenu output structure as below by using mod_mainmenu template. Note here class="box1", class="box2", class="box3", class="box4" will fetched dynamically. <ul class="menu"> <li class=""> <a href="#" class="box1"><span>Menu 1</span></a> </li> <li class="current"> <a href="#" class="box2"><span>Menu 2</span></a> <ul class="box2"> <li><a href="#">Sub Menu 1</a></li> <li><a href="#">Sub Menu 2</a></li> <li><a href="#">Sub Menu 3</a></li> </ul> </li> <li class=""> <a href="#" class="box3"><span>Menu 3</span></a> </li> <li class=""> <a href="#" class="box4"><span>Menu 4</span></a> </li> </ul>

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  • derived class as default argument g++

    - by Vincent
    Please take a look at this code: template<class T> class A { class base { }; class derived : public A<T>::base { }; public: int f(typename A<T>::base& arg = typename A<T>::derived()) { return 0; } }; int main() { A<int> a; a.f(); return 0; } Compiling generates the following error message in g++: test.cpp: In function 'int main()': test.cpp:25: error: default argument for parameter of type 'A<int>::base&' has type 'A<int>::derived' The basic idea (using derived class as default value for base-reference-type argument) works in visual studio, but not in g++. I have to publish my code to the university server where they compile it with gcc. What can I do? Is there something I am missing?

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  • How to generate lots of redundant ajax elements like checkboxes and pulldowns in Django?

    - by iJames
    Hello folks. I've been getting lots of answers from stackoverflow now that I'm in Django just be searching. Now I hope my question will also create some value for everybody. In choosing Django, I was hoping there was some similar mechanism to the way you can do partials in ROR. This was going to help me in two ways. One was in generating repeating indexed forms or form elements, and also in rendering only a piece of the page on the round trip. I've done a little bit of that by using taconite with a simple URL click but now I'm trying to get more advanced. This will focus on the form issue which boils down to how to iterate over a secondary object. If I have a list of photo instances, each of which has a couple of parameters, let's say a size and a quantity. I want to generate form elements for each photo instance separately. But then I have two lists I want to iterate on at the same time. Context: photos : Photo.objects.all() and forms = {} for photo in photos: forms[photo.id] = PhotoForm() In other words we've got a list of photo objects and a dict of forms based on the photo.id. Here's an abstraction of the template: {% for photo in photos %} {% include "photoview.html" %} {% comment %} So here I want to use the photo.id as an index to get the correct form. So that each photo has its own form. I would want to have a different action and each form field would be unique. Is that possible? How can I iterate on that? Thanks! {% endcomment %} Quantity: {{ oi.quantity }} {{ form.quantity }} Dimensions: {{ oi.size }} {{ form.size }} {% endfor %} What can I do about this simple case. And how can I make it where every control is automatically updating the server instead of using a form at all? Thanks! James

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  • How to treat Base* pointer as Derived<T>* pointer?

    - by dehmann
    I would like to store pointers to a Base class in a vector, but then use them as function arguments where they act as a specific class, see here: #include <iostream> #include <vector> class Base {}; template<class T> class Derived : public Base {}; void Foo(Derived<int>* d) { std::cerr << "Processing int" << std::endl; } void Foo(Derived<double>* d) { std::cerr << "Processing double" << std::endl; } int main() { std::vector<Base*> vec; vec.push_back(new Derived<int>()); vec.push_back(new Derived<double>()); Foo(vec[0]); Foo(vec[1]); delete vec[0]; delete vec[1]; return 0; } This doesn't compile: error: call of overloaded 'Foo(Base*&)' is ambiguous Is it possible to make it work? I need to process the elements of the vector differently, according to their int, double, etc. types.

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  • Compile time type determination in C++

    - by dicroce
    A coworker recently showed me some code that he found online. It appears to allow compile time determination of whether a type has an "is a" relationship with another type. I think this is totally awesome, but I have to admit that I'm clueless as to how this actually works. Can anyone explain this to me? template<typename BaseT, typename DerivedT> inline bool isRelated(const DerivedT&) { DerivedT derived(); char test(const BaseT&); // sizeof(test()) == sizeof(char) char (&test(...))[2]; // sizeof(test()) == sizeof(char[2]) struct conversion { enum { exists = (sizeof(test(derived())) == sizeof(char)) }; }; return conversion::exists; } Once this function is defined, you can use it like this: #include <iostream> class base {}; class derived : public base {}; class unrelated {}; int main() { base b; derived d; unrelated u; if( isRelated<base>( b ) ) std::cout << "b is related to base" << std::endl; if( isRelated<base>( d ) ) std::cout << "d is related to base" << std::endl; if( !isRelated<base>( u ) ) std::cout << "u is not related to base" << std::endl; }

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  • How to stop Django from adding extra html elements to rendered widgets.

    - by stinkypyper
    I have a Django radio button group that renders to HTML as follows: <ul> <li><label for="id_package_id_0"><input type="radio" id="id_package_id_0" value="1" name="package_id" /> Test 256</label></li> <li><label for="id_package_id_1"><input type="radio" id="id_package_id_1" value="2" name="package_id" /> Test 384</label></li> <li><label for="id_package_id_2"><input type="radio" id="id_package_id_2" value="3" name="package_id" /> Test 512</label></li> <li><label for="id_package_id_3"><input type="radio" id="id_package_id_3" value="4" name="package_id" /> Test 768</label></li> <li><label for="id_package_id_4"><input type="radio" id="id_package_id_4" value="5" name="package_id" /> Test 1024</label></li> </ul> I need it to render without being a list. I am a aware of form.as_p, form.as_table, and form.as_ul. They will not help me as they continue to add extra HTML tags. As well, I am not using the form object in it's absolute entirety, just for validation. I am doing a custom template for the form already, but wish to continue to the radio widget.

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  • Firefox handles xxx.submit(), Safari doesn't ... what can be done?

    - by Prairiedogg
    I'm trying to make a pull down menu post a form when the user selects (releases the mouse) on one of the options from the menu. This code works fine in FF but Safari, for some reason, doesn't submit the form. I re-wrote the code using jquery to see if jquery's .submit() implementation handled the browser quirks better. Same result, works in FF doesn't work in safari. The following snippets are from the same page, which has some django template language mixed in. Here's the vanilla js attempt: function formSubmit(lang) { if (lang != '{{ LANGUAGE_CODE }}') { document.getElementById("setlang_form").submit(); } } Here's the jquery attempt: $(document).ready(function() { $('#lang_submit').hide() $('#setlang_form option').mouseup(function () { if ($(this).attr('value') != '{{ LANGUAGE_CODE }}') { $('#setlang_form').submit() } }); }); and here's the form: <form id="setlang_form" method="post" action="{% url django.views.i18n.set_language %}"> <fieldset> <select name="language"> {% for lang in interface_languages %} <option value="{{ lang.code }}" onmouseup="formSubmit('{{ lang.name }}')" {% ifequal lang.code LANGUAGE_CODE %}selected="selected"{% endifequal %}>{{ lang.name }}</option> {% endfor %} </select> </fieldset> </form> My question is, how can I get this working in Safari?

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  • PHP: Opening/closing tags & performance?

    - by Tom
    Hi, This may be a silly question, but as someone relatively new to PHP, I'm wondering if there are any performance-related issues to frequently opening and closing PHP tags in HTML template code, and if so, what might be best practices in terms of working with php tags? My question is not about the importance/correctness of closing tags, or about which type of code is more readable than another, but rather about how the document gets parsed/executed and what impact it might have on performance. To illustrate, consider the following two extremes: Mixing PHP and HTML tags: <?php echo '<tr> <td>'.$variable1.'</td> <td>'.$variable2.'</td> <td>'.$variable3.'</td> <td>'.$variable4.'</td> <td>'.$variable5.'</td> </tr>' ?> // PHP tag opened once Separating PHP and HTML tags: <tr> <td><?php echo $variable1 ?></td> <td><?php echo $variable2 ?></td> <td><?php echo $variable3 ?></td> <td><?php echo $variable4 ?></td> <td><?php echo $variable5 ?></td> </tr> // PHP tag opened five times Would be interested in hearing some views on this, even if it's just to hear that it makes no difference. Thanks.

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  • Django Getting RequestContext in custom tag

    - by greggory.hz
    I'm trying to create a custom tag. Inside this custom tag, I want to be able to have some logic that checks if the user is logged in, and then have the tag rendered accordingly. This is what I have: class UserActionNode(template.Node): def __init__(self): pass def render(self, context): if context.user.is_authenticated(): return render_to_string('layout_elements/sign_in_register.html'); else: return render_to_string('layout_elements/logout_settings.html'); def user_actions(parser, test): return UserActionNode() register.tag('user_actions', user_actions) When I run this, I get this error: Caught AttributeError while rendering: 'Context' object has no attribute 'user' The view that renders this looks like this: return render_to_response('start/home.html', {}, context_instance=RequestContext(request)) Why doesn't the tag get a RequestContext object instead of the Context object? How can I get the tag to receive the RequestContext instead of the Context? EDIT: Whether or not it's possible to get a RequestContext inside a custom tag, I'd still be interested to know the "correct" or best way to determine a user's authentication state from within the custom tag. If that's not possible, then perhaps that kind of logic belongs elsewhere? Where?

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  • C++: Constructor/destructor unresolved when not inline?

    - by Anamon
    In a plugin-based C++ project, I have a TmpClass that is used to exchange data between the main application and the plugins. Therefore the respective TmpClass.h is included in the abstract plugin interface class that is included by the main application project, and implemented by each plugin. As the plugins work on STL vectors of TmpClass instances, there needs to be a default constructor and destructor for the TmpClass. I had declared these in TmpClass.h: class TmpClass { TmpClass(); ~TmpClass(); } and implemented them in TmpClass.cpp. TmpClass::~TmpClass() {} TmpClass::TmpClass() {} However, when compiling plugins this leads to the linker complaining about two unresolved externals - the default constructor and destructor of TmpClass as required by the std::vector<TmpClass> template instantiation - even though all other functions I declare in TmpClass.h and implement in TmpClass.cpp work. As soon as I remove the (empty) default constructor and destructor from the .cpp file and inline them into the class declaration in the .h file, the plugins compile and work. Why is it that the default constructor and destructor have to be inline for this code to compile? Why does it even maatter? (I'm using MSVC++8).

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  • CodeIgniter - the right way to create "block" elements on web page

    - by kikkoman90
    Hello. I've been searching for a solutions for this problem a while but haven't seen any "valid mvc" solution for this. I hope I can explain my problem clearly enough for you guys. I need to create a dynamic block of HTML on my website. (eg. a block containing user's latest blog comments). I have a template view file (a file containing header, content container and a footer) where I need to add some content AND this block element. The problem is that I don't want to duplicate this block code on every controller. It just feels stupid and I'm sure there's a better way to do this than just duplicating same stuff all over again on all the controller files? I can add view inside another view just fine, but what bugs me is how to actually generate that dynamic content to this block's view-file. I can't call controller from view file, controller from controller filem or model from view file because what I understand that just isn't the "mvc" way? Anyone got any tricks or tips for this?

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  • Strange overloading rules in C++

    - by bucels
    I'm trying to compile this code with GCC 4.5.0: #include <algorithm> #include <vector> template <typename T> void sort(T, T) {} int main() { std::vector<int> v; sort(v.begin(), v.end()); } But it doesn't seem to work: $ g++ -c nm.cpp nm.cpp: In function ‘int main()’: nm.cpp:9:28: error: call of overloaded ‘sort(std::vector<int>::iterator, std::vector<int>::iterator)’ is ambiguous nm.cpp:4:28: note: candidates are: void sort(T, T) [with T = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] /usr/lib/gcc/i686-pc-linux-gnu/4.5.0/../../../../include/c++/4.5.0/bits/stl_algo.h:5199:69: note: void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] Comeau compiles this code without errors. (4.3.10.1 Beta2, strict C++03, no C++0x) Is this valid C++?

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  • Overwriting a range of bits in an integer in a generic way

    - by porgarmingduod
    Given two integers X and Y, I want to overwrite bits at position P to P+N. Example: int x = 0xAAAA; // 0b1010101010101010 int y = 0x0C30; // 0b0000110000110000 int result = 0xAC3A; // 0b1010110000111010 Does this procedure have a name? If I have masks, the operation is easy enough: int mask_x = 0xF00F; // 0b1111000000001111 int mask_y = 0x0FF0; // 0b0000111111110000 int result = (x & mask_x) | (y & mask_y); What I can't quite figure out is how to write it in a generic way, such as in the following generic C++ function: template<typename IntType> IntType OverwriteBits(IntType dst, IntType src, int pos, int len) { // If: // dst = 0xAAAA; // 0b1010101010101010 // src = 0x0C30; // 0b0000110000110000 // pos = 4 ^ // len = 8 ^------- // Then: // result = 0xAC3A; // 0b1010110000111010 } The problem is that I cannot figure out how to make the masks properly when all the variables, including the width of the integer, is variable. Does anyone know how to write the above function properly?

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  • Is it possible to implement events in C++?

    - by acidzombie24
    I wanted to implement a C# event in C++ just to see if i could do it. I got stuck, i know the bottom is wrong but what i realize my biggest problem is... How do i overload the () operator to be whatever is in T in this case int func(float)? I cant? can i? Can i implement a good alternative? #include <deque> using namespace std; typedef int(*MyFunc)(float); template<class T> class MyEvent { deque<T> ls; public: MyEvent& operator +=(T t) { ls.push_back(t); return *this; } }; static int test(float f){return (int)f; } int main(){ MyEvent<MyFunc> e; e += test; }

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  • Null pointer to struct which has zero size (empty)... It is a good practice?

    - by ProgramWriter
    Hi2All.. I have some null struct, for example: struct null_type { NullType& someNonVirtualMethod() { return *this; } }; And in some function i need to pass reference to this type. Reason: template <typename T1 = null_type, typename T2 = null_type, ... > class LooksLikeATupleButItsNotATuple { public: LooksLikeATupleButItsNotATuple(T1& ref1 = defParamHere, T2& ref2 = andHere..) : _ref1(ref1), _ref2(ref2), ... { } void someCompositeFunctionHere() { _ref1.someNonVirtualMethod(); _ref2.someNonVirtualMethod(); ... } private: T1& _ref1; T2& _ref2; ...; }; It is a good practice to use null reference as a default parameter?: *static_cast<NullType*>(0) It works on MSVC, but i have some doubts...

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  • How to access a named element in a control that inherits from a templated control

    - by Mrt
    Hello this is similar to http://stackoverflow.com/questions/2620165/how-to-access-a-named-element-of-a-derived-user-control-in-silverlight with the difference is inheriting from a templated control, not a user control. I have a templated control called MyBaseControl <Style TargetType="Problemo:MyBaseControl"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Problemo:MyBaseControl"> <Grid x:Name="LayoutRoot" Background="White"> <Border Name="HeaderControl" Background="Red" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> public class MyBaseControl : Control { public UIElement Header { get; set; } public MyBaseControl() { DefaultStyleKey = typeof(MyBaseControl); } public override void OnApplyTemplate() { base.OnApplyTemplate(); var headerControl = GetTemplateChild("HeaderControl") as ContentPresenter; if (headerControl != null) headerControl.Content = Header; } } I have another control called myControl which inherits from MyBaseControl Control <me:MyBaseControl x:Class="Problemo.MyControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" xmlns:me="clr-namespace:Problemo" d:DesignHeight="300" d:DesignWidth="400"> <me:MyBaseControl.Header> <TextBlock Name="xxx" /> </me:MyBaseControl.Header> </me:MyBaseControl> public partial class MyControl : MyBaseControl { public string Text { get; set; } public MyControl(string text) { InitializeComponent(); Text = text; Loaded += MyControl_Loaded; } void MyControl_Loaded(object sender, RoutedEventArgs e) { base.ApplyTemplate(); xxx.Text = Text; } } The issue is xxx is null. How do I access the xxx control in the code behind ?

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  • WPF Custom Control - Designer looks fine, but I get a runtime issue...

    - by myermian
    MainWindow.xaml <Window x:Class="MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:my="clr-namespace:MyStuff;assembly=MyStuff" Title="MainWindow" Height="350" Width="525"> <Grid> <TabControl Margin="5"> <TabItem Header="Start Page" /> <my:XTabItem Header="Tab 1" Image="Resources/icon1.png" /> </TabControl> </Grid> </Window> Generic.xaml <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:MyStuff" > <!-- XTabItem --> <Style TargetType="{x:Type local:XTabItem}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type local:XTabItem}"> <Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}"> <StackPanel Orientation="Horizontal"> <Image Source="{Binding Path=Image, RelativeSource={RelativeSource TemplatedParent}}" Stretch="UniformToFill" MaxHeight="24" /> <TextBlock Text="{TemplateBinding Header}" /> <Button Content="X" /> </StackPanel> </Border> </ControlTemplate> </Setter.Value> </Setter> </Style> </ResourceDictionary> XTabItem.cs using System; using System.ComponentModel; using System.Windows; using System.Windows.Controls; using System.Windows.Media; namespace MyStuff { public class XTabItem : TabItem { #region Dependency Properties public static readonly DependencyProperty ImageProperty; #endregion #region Constructors / Initializer static XTabItem() { //Initialize the control as "lookless". DefaultStyleKeyProperty.OverrideMetadata(typeof(XTabItem), new FrameworkPropertyMetadata(typeof(XTabItem))); //Setup the dependency properties. ImageProperty = DependencyProperty.Register("Image", typeof(ImageSource), typeof(XTabItem), new UIPropertyMetadata(null)); } #endregion #region Custom Control Properties (Image) /// <summary> /// The image (icon) displayed by inside the tab header. /// </summary> /// <remarks>The image is specified in XAML as an absolute or relative path.</remarks> [Description("The image displayed by the button"), Category("Optional Properties")] public ImageSource Image { get { return (ImageSource)GetValue(ImageProperty); } set { SetValue(ImageProperty, value); } } #endregion } } Exception at line #9 () : XamlParseException : 'Provide value on 'System.Windows.Baml2006.TypeConverterMarkupExtension' threw an exception.' Line number '9' and line position '27'.

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  • Is there any reasonable use of a function returning an anonymous struct?

    - by Akanksh
    Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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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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  • WTF is wtf? (in WebKit code base)

    - by Motti
    I downloaded Chromium's code base and ran across the WTF namespace. namespace WTF { /* * C++'s idea of a reinterpret_cast lacks sufficient cojones. */ template<typename TO, typename FROM> TO bitwise_cast(FROM in) { COMPILE_ASSERT(sizeof(TO) == sizeof(FROM), WTF_wtf_reinterpret_cast_sizeof_types_is_equal); union { FROM from; TO to; } u; u.from = in; return u.to; } } // namespace WTF Does this mean what I think it means? Could be so, the bitwise_cast implementation specified here will not compile if either TO or FROM is not a POD and is not (AFAIK) more powerful than C++ built in reinterpret_cast. The only point of light I see here is the nobody seems to be using bitwise_cast in the Chromium project. I see there's some legalese so I'll put in the little letters to keep out of trouble. /* * Copyright (C) 2008 Apple Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

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  • c++ class member functions selected by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instatiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • c++ class member functions instatiated by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched stackoverflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state info was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (vc++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

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  • fancybox image sometimes renders outside box

    - by Colleen
    I have the following django template: <script type="text/javascript" src="{{ STATIC_URL }}js/ jquery.fancybox-1.3.4.pack.js"></script> <link rel="stylesheet" href="{{ STATIC_URL }}css/ jquery.fancybox-1.3.4.css" type="text/css" media="screen" /> {% include "submission-form.html" with section="photos" %} <div class="commentables"> {% load thumbnail %} {% for story in objects %} <div class="image {% if forloop.counter|add:"-1"| divisibleby:picsinrow %}left{% else %}{% if forloop.counter| divisibleby:picsinrow %}right{% else %}middle{% endif %}{% endif %}"> {% if story.image %} {% thumbnail story.image size crop="center" as full_im %} <a rel="gallery" href="{% url post slug=story.slug %}"> <img class="preview" {% if story.title %} alt="{{ story.title }}" {% endif %} src="{{ full_im.url }}" full- image="{% if story.image_url %}{{ story.image_url }}{% else %} {{ story.image.url }}{% endif %}"> </a> {% endthumbnail %} {% else %} {% if story.image_url %} {% thumbnail story.image_url size crop="center" as full_im %} <a rel="gallery" href="{% url post slug=story.slug %}"> <img class="preview" {% if story.title %} alt="{{ story.title }}" {% endif %} src="{{ full_im.url }}" full- image="{{ story.image_url }}"> </a> {% endthumbnail %} {% endif %} {% endif %} </div> {% endfor %} {% if rowid != "last" %} <br style="clear: both" /> {% endif %} {% if not no_more_button %} <p style="text-align: right;" class="more-results"><a href="{% url images school_slug tag_slug %}">more...</a></p> {% endif %} </div> <script> $(document).ready(function(){ function changeattr(e){ var f = $(e.clone()); $(f.children()[0]).attr('src', $(f.children() [0]).attr("full-image")); $(f.children()[0]).attr('height', '500px'); return f[0].outerHTML; } $('.image a').each(function(idx, elem) { var e = $(elem); e.fancybox({ title: $(e.children()[0]).attr('alt'), content: changeattr(e) }); }); }); </script> and I'm occasionally getting weird display errors where the box will either not render anything at all (so it will show up as just a thin white bar, basically) or it will render only about 30 px wide, and position itself halfway down the page. In both cases, if I inspect element, I can see the "shadow" of the full picture, at the right size, with the right url. Image source doesnt' seem to make a difference, I'm getting no errors, and this is happening in both chrome and firefox. Does anyone have any ideas?

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  • C++ class member functions instantiated by traits

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched Stack Overflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate non-virtual member functions? The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state information was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (VC++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice?

    Read the article

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