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  • Can I write a test that succeeds if and only if a statement does not compile?

    - by Billy ONeal
    I'd like to prevent clients of my class from doing something stupid. To that end, I have used the type system, and made my class only accept specific types as input. Consider the following example (Not real code, I've left off things like virtual destructors for the sake of example): class MyDataChunk { //Look Ma! Implementation! }; class Sink; class Source { virtual void Run() = 0; Sink *next_; void SetNext(Sink *next) { next_ = next; } }; class Sink { virtual void GiveMeAChunk(const MyDataChunk& data) { //Impl }; }; class In { virtual void Run { //Impl } }; class Out { }; //Note how filter and sorter have the same declaration. Concrete classes //will inherit from them. The seperate names are there to ensure only //that some idiot doesn't go in and put in a filter where someone expects //a sorter, etc. class Filter : public Source, public Sink { //Drop objects from the chain-of-command pattern that don't match a particular //criterion. }; class Sorter : public Source, public Sink { //Sorts inputs to outputs. There are different sorters because someone might //want to sort by filename, size, date, etc... }; class MyClass { In i; Out o; Filter f; Sorter s; public: //Functions to set i, o, f, and s void Execute() { i.SetNext(f); f.SetNext(s); s.SetNext(o); i.Run(); } }; What I don't want is for somebody to come back later and go, "Hey, look! Sorter and Filter have the same signature. I can make a common one that does both!", thus breaking the semantic difference MyClass requires. Is this a common kind of requirement, and if so, how might I implement a test for it?

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  • How can I reuse a base class function in a derived class

    - by Armen Ablak
    Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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  • Why is this std::bind not converted to std::function?

    - by dauphic
    Why is the nested std::bind in the below code not implicitly converted to an std::function<void()> by any of the major compilers (VS2010/2012, gcc, clang)? Is this standard behavior, or a bug? #include <functional> void bar(int, std::function<void()>) { } void foo() { } int main() { std::function<void(int, std::function<void()>)> func; func = std::bind(bar, 5, std::bind(foo)); std::cin.get(); return 0; }

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  • Is there a way to find out whether a class is a direct base of another class?

    - by user176168
    Hi I'm wondering whether there is a way to find out whether a class is a direct base of another class i.e. in boost type trait terms a is_direct_base_of function. As far as I can see boost doesn't see to support this kind of functionality which leads me to think that its impossible with the current C++ standard. The reason I want it is to do some validation checking on two macro's that are used for a reflection system to specify that one class is derived from another e.g. header.h: #define BASE A #define DERIVED B class A {}; class B : public A { #include <rtti.h> }; rtti.h: // I want to check that the two macro's are correct with a compile time assert Rtti<BASE, DERIVED> m_rtti; Although the macro's seem unnecessary in this simple example in my real world scenario rtti.h is a lot more complex. One possible avenue would be to compare the size of the this pointer with the size of a this pointer cast to the base type and some how trying to figure out whether its the size of the base class itself away or something (yeah your right I don't know how that would work either! lol)

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  • Using tinybutstrong templating system, how do I have a (secondary) mysql query (sub-block), inside a

    - by desbest
    This is the code that works well. $TBS->MergeBlock("items",$conn,"SELECT * FROM items WHERE categoryid = $getcategory"); and it has a good job of looping the items with no problem. <tr id="itemid_[items.id;block=tr]"> <td height="30"> <!-- <img src="move.png" align="left" style="margin-right: 8px;"> --> <div class="lowlight">[items.title] </div> </td> <td height="30"> <div class="editable" itemid="$item[id]">[items.quantity]</div> </td> <td height="30"> <!-- <img src="pencil.png" id="edititem"width="24" height="24"> --> &nbsp; &nbsp; &nbsp; &nbsp;<img src="icons/folder.png" id="category_[items.categoryid]";" class="changecategory" categoryid="[items.categoryid]" itemid="[items.id]" itemtitle="[items.title]" title="Change category" width="24" height="24"> &nbsp; &nbsp; &nbsp; &nbsp; <a href="index.php?category=[var.getcategory]&deleteitem=[items.id]" title="Delete item" onclick="return confirm('Are you sure you want to delete [items.title]?')"><img src="icons/trash.png" id="deleteitem" width="24" height="24"></a> </td> </tr> This is where the problem lies. In the table row I would like a secondary mysql merge block based on the id column that the primary (items) mysql table has. This means that ideally I would love to do this. $TBS->MergeBlock("fields",$conn,"SELECT * FROM items WHERE categoryid = [items.id]"); So then when I used [fields.value;block=div] inside the table row, it would pick up the a row from the fields table based on the primary mysql query. It would recognise what the id is for the merged block and perform a mysql query based on a variable that that block has. So that's what I would like to do and that's what I call a secondary mysql merge block. This is what I attempted by using the sub-blocks example and modifying it. index.html <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>TinyButStrong - Examples - subblocks</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link href="tbs_us_examples_0styles.css" rel="stylesheet" type="text/css"> <style type="text/css"> <!-- .border02 { border: 2px solid #39C; } .border03 { border: 2px solid #396; } --> </style> </head> <body> <table width="400" align="center" cellpadding="5" cellspacing="0" style="border-collapse:collapse;"> <tr> <td class="border02"><strong>Item name:</strong> [item.title;block=tr] , <strong>Item quantity:</strong> [item.quantity]<br> <table border="1" align="center" cellpadding="2" cellspacing="0"> <tr bgcolor="#CACACA"> <td width="30"><u>Position</u></td> <td width="150"><u>Attribute</u></td> <td width="50"><u>Value</u></td> <td width="100"><div align="center"><u>Date Number</u></div></td> </tr> <tr bgcolor="#F0F0F0"> <td>[field.#]</td> <td>[field.attribute;block=tr;p1=[item.id]] <br><b>[item.id]</b> </td> <td><div align="right">[field.value]</div></td> <td><div align="center">[field.datenumber;frm='mm-dd-yyyy']</div></td> </tr> </table> </td> </tr> </table> </body> </html> index.php <?php require_once('../stockman-v3/tbs_class.php'); require_once('../stockman-v3/config.php'); // Create data $TeamList[0] = array('team'=>'Eagle' ,'total'=>'458'); //{ $TeamList[0]['matches'][] = array('town'=>'London','score'=>'253','date'=>'1999-11-30'); $TeamList[0]['matches'][] = array('town'=>'Paris' ,'score'=>'145','date'=>'2002-07-24'); $TeamList[1] = array('team'=>'Goonies','total'=>'281'); $TeamList[1]['matches'][] = array('town'=>'New-York','score'=>'365','date'=>'2001-12-25'); $TeamList[1]['matches'][] = array('town'=>'Madrid' ,'score'=>'521','date'=>'2004-01-14'); // } $TeamList[2] = array('team'=>'MIB' ,'total'=>'615'); // { $TeamList[2]['matches'][] = array('town'=>'Dallas' ,'score'=>'362','date'=>'2001-01-02'); $TeamList[2]['matches'][] = array('town'=>'Lyon' ,'score'=>'321','date'=>'2002-11-17'); $TeamList[2]['matches'][] = array('town'=>'Washington','score'=>'245','date'=>'2003-08-24'); // } $TBS = new clsTinyButStrong; $TBS->LoadTemplate('index3.html'); // Automatic subblock $TBS->MergeBlock("item",$conn,"SELECT * FROM items"); $TBS->MergeBlock("field",$conn,"SELECT * FROM fields WHERE itemid='[%p1%]' "); $TBS->MergeBlock('teamKEY',$TeamList); // Subblock with a dynamic query //$TBS->MergeBlock('match','array','TeamList[%p1%][matches]'); $TBS->MergeBlock("match",$conn,"SELECT * FROM fields WHERE id='[%p1%]' "); $TBS->Show(); ?> please note what i am trying to do If I was to change $TBS->MergeBlock("field",$conn,"SELECT * FROM fields WHERE itemid='[%p1%]' "); to... $TBS->MergeBlock("field",$conn,"SELECT * FROM fields"); It would show all the items.

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  • How can I add reflection to a C++ application?

    - by Nick
    I'd like to be able to introspect a C++ class for its name, contents (i.e. members and their types) etc. I'm talking native C++ here, not managed C++, which has reflection. I realise C++ supplies some limited information using RTTI. Which additional libraries (or other techniques) could supply this information?

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  • Use Shakespeare-text and external file

    - by Adam
    How can I convert the below example to use an external file instead of the embedded lazy text quasi quotes? {-# LANGUAGE QuasiQuotes, OverloadedStrings #-} import Text.Shakespeare.Text import qualified Data.Text.Lazy.IO as TLIO import Data.Text (Text) import Control.Monad (forM_) data Item = Item { itemName :: Text , itemQty :: Int } items :: [Item] items = [ Item "apples" 5 , Item "bananas" 10 ] main :: IO () main = forM_ items $ \item -> TLIO.putStrLn [lt|You have #{show $ itemQty item} #{itemName item}.|] This is from the yesod online book.

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  • Passing markup into a Rails Partial

    - by 1ndivisible
    Is there any way of doing something equivilant to this: <%= render partial: 'shared/outer' do %> <%= render partial: 'shared/inner' %> <% end %> Resulting in <div class="outer"> <div class="inner"> </div> </div> Obviously there would need to be a way of marking up 'shared/outer.html.erb' to indicate where the passed in partial should be rendered: <div class="outer"> <% render Here %> </div>

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  • Which Java MVC frameworks integrate easily with StringTemplate?

    - by Daniel Jomphe
    It's hard to see how StringTemplate integrates easily (or not) with popular Java web MVC frameworks. Which Java MVC frameworks integrate easily with StringTemplate? A good answer: mentions one solution to integrate with a framework, includes a link to something useful and applicable, like: a tutorial, or documentation, or a reference to source code: free, and open source or public domain. Readers/Voters, please vote for a solution if you know it's true and great. In the scope of this question, I am not interested in any other templating engine than StringTemplate.

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  • How do I translate a ISO 8601 datetime string into a Python datetime object?

    - by Andrey Fedorov
    I'm getting a datetime string in a format like "2009-05-28T16:15:00" (this is ISO 8601, I believe) one hack-ish option seems to be to parse the string using time.strptime and passing the first 6 elements of the touple into the datetime constructor, like: datetime.datetime(*time.strptime("2007-03-04T21:08:12", "%Y-%m-%dT%H:%M:%S")[:6]) I haven't been able to find a "cleaner" way of doing this, is there one?

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  • `.' cannot appear in a constant-expression

    - by Amir Rachum
    Hi all, I'm getting the following error: `.' cannot appear in a constant-expression for this function (line 4): bool Covers(const Region<C,V,D>& other) const { const Region& me = *this; for (unsigned d = 0; d < D; d++) { if (me[d].min > other[d].min || me[d].max < other[d].max) { return false; } } can anyone explain the problem please?

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  • Updating several records at once using Django

    - by 47
    I want to create a list of records with checkboxes on the left side....kinda like the inbox in Gmail. Then if a user selects some or all of these checkboxes, then the selected record(s) can be updated (only one field will be updated BTW), possibly by clicking a button. I'm stuck on how to do this though....ideas?

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  • How can I have multiple navigation paths with Django, like a simplifies wizard path and a full path?

    - by Zeta
    Lets say I have an application with a structure such as: System set date set name set something Other set death ray target calibrate and I want to have "back" and "next" buttons on a page. The catch is, if you're going in via the "wizard", I want the nav path to be something like "set name" - "set death ray target" - "set name". If you go via the Advanced options menu, I want to just iterate options... "set date" - "set name" - "set something" - "set death ray target" - calibrate. So far, I'm thinking I have to use different URIs, but that's that. Any ideia how this could be done? Thanks.

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  • In Jeditable, how do I make it so that when I click the div to edit, the text box content has initial value that is processed?

    - by TIMEX
    When the user clicks on the div, jeditable will make a text box. However, I want the initial text to be done with function stripTags(), instead of what's on the page. The reason is that I'm using some URL techniques to turn plain text links into URLs. When the user clicks on the div, jeditable is turning them into <a href=>..</a> Is there a "beforeSubmit" option in jeditable? http://www.appelsiini.net/projects/jeditable

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  • In the generic programming/TMP world what exactly is a model / a policy and a "concept" ?

    - by Hassan Syed
    I'd like to know the precise yet succinct definitions of these three concepts in one place. The quality of the answer should depend on the following two points. Show a simple code snippet to show how and what the concept/technique is used for. Be simple enough to understand so that a programmer without any exposure to this area can grasp it. Note: There are probably many correct answers since each concept has many different facets. If there are a lot of good answers I will eventually turn the question into CW and aggregate the answers. -- Post Accept Edit -- Boost has a nice article on generic programming concepts

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  • "Automatic" class proxy in C++

    - by PierreBdR
    I need to allow the user to change members of two data structures of the same type at the same time. For example: struct Foo { int a, b; } Foo a1 = {1,2}, a2 = {3,4}; dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,2} I have a class that works and that change first a1 and then copy a1 into a2. This is fine as long as: the class copied is small the user doesn't mind about everything being copied, not only the part modified. Is there a way to obtain this behavior: dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,4} I am opened to alternative syntax, but they should stay simple, and I would like to avoid things like: set_members(a1, a2, &Foo::a, 5); members(a1, a2, &Foo::a) = 5; or anything involving specifying explictely &Foo::

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  • Rvalues in C++03

    - by DeadMG
    How can you tell whether or not a given parameter is an rvalue in C++03? I'm writing some very generic code and am in need of taking a reference if possible, or constructing a new object otherwise. Can I overload to take by-value as well as by-reference and have the rvalue returns call the by-value function? Or do I have a very sickening feeling that this is why rvalue references are in C++0x?

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  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

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  • Magento - How can I move the Navigation Block to be in the right column?

    - by Hank
    I've been editing Magento's default CSS to change the look and have come to a point where I want to move around some content blocks. I've killed off the left column through CSS .col-left { display: none; } And then increased the width of the main content part to create a 'two column layout'. What I want to do now is move the navigation for the categories into the right column. I just have no idea how... How do I move content blocks around in Magento? :/

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  • How to save link with tag e parameters in TextField

    - by xRobot
    I have this simple Post model: class Post(models.Model): title = models.CharField(_('title'), max_length=60, blank=True, null=True) body = models.TextField(_('body')) blog = models.ForeignKey(Blog, related_name="posts") user = models.ForeignKey(User) I want that when I insert in the form the links, the these links are saved in the body from this form: http://www.example.com or www.example.com to this form ( with tag and rel="nofollow" parameter ): <a href="http://www.example.com" rel="nofollow">www.example.com</a> How can I do this ? Thanks ^_^

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  • How to easily apply a function to a collection in C++

    - by Jesse Beder
    I'm storing images as arrays, templated based on the type of their elements, like Image<unsigned> or Image<float>, etc. Frequently, I need to perform operations on these images; for example, I might need to add two images, or square an image (elementwise), and so on. All of the operations are elementwise. I'd like get as close as possible to writing things like: float Add(float a, float b) { return a+b; } Image<float> result = Add(img1, img2); and even better, things like complex ComplexCombine(float a, float b) { return complex(a, b); } Image<complex> result = ComplexCombine(img1, img2); or struct FindMax { unsigned currentMax; FindMax(): currentMax(0) {} void operator(unsigned a) { if(a > currentMax) currentMax = a; } }; FindMax findMax; findMax(img); findMax.currentMax; // now contains the maximum value of 'img' Now, I obviously can't exactly do that; I've written something so that I can call: Image<float> result = Apply(img1, img2, Add); but I can't seem to figure out a generic way for it to detect the return type of the function/function object passed, so my ComplexCombine example above is out; also, I have to write a new one for each number of arguments I'd like to pass (which seems inevitable). Any thoughts on how to achieve this (with as little boilerplate code as possible)?

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  • C++ Generic List Assignment

    - by S73417H
    I've clearly been stuck in Java land for too long... Is it possible to do the C++ equivalent of the following Java code: // Method List<Bar> getBars() { return new LinkedList<Bar>(); } // Assignment statement. List<Foo> stuff = getBars(); Where Foo is a sub-class of Bar. So in C++.... std::list<Bar> & getBars() { std::list<Bar> bars; return bars; } std::list<Foo> stuff = getBars(); Hope that makes sense....

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