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• Alternative to c++ static virtual methods

  - by Jaime Pardos

  In C++ is not possible to declare a static virtual function, neither cast a non-static function to a C style function pointer. Now, I have a plain ol' C SDK that uses function pointers heavily. I have to fill a structure with several function pointers. I was planning to use an abstract class with a bunch of static pure virtual methods, and redefine them in derived classes and fill the structure with them. It wasn't until then that I realized that static virtual are not allowed in C++. Is there any good alternative? The best I can think of is defining some pure virtual methods GetFuncA(), GetFuncB(),... and some static members FuncA()/FuncB() in each derived class, which would be returned by the GetFuncX(). Then a function in the abstract class would call those functions to get the pointers and fill the structure.

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• Delphi component or library to display mathematical expressions

  - by Svein Bringsli

  I'm looking for a simple component that displays mathematical expressions in Delphi. When I started out I thought it would be easy to find something on the net, but it turns out it was harder than anticipated. There are lots and lots of components that will parse mathematical expressions, but few (none?) that will display them. Ideally I would like a component as simple as a TLabel, where I could set the caption to some expression and it would be displayed correctly, but some sort of library that let's me draw expressions to a canvas would also be sufficient for my needs. Update: I'm not talking about plotting graphs of functions or something like that. I want to display (for instance) (X^2+3)/X like this:

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• Build a JavaScript wrapper for a rails-generated XML API?

  - by Thor Thurn

  I am working with a large website written in Ruby on Rails. Thanks to the support for REST in Rails 2, the site's business logic is all accessible via a consistent XML API. Now I want to be able to easily write one or more JavaScript frontends to the site that interact with the generated Rails XML API. Ideally, an automated wrapper for the API could be created in JavaScript, since this would minimize the effort required in writing XML processing code for the more than 500 API functions. How, then, can I automatically generate a wrapper around a given XML API in JavaScript so that it's more pleasant to work with? I've worked with solutions of this nature for Java that generate classes and methods to wrap an API, so my current thinking is that I want something of that nature for JavaScript. I'd be open to an alternative take on the problem, though.

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• Is it possible to create thread-safe collections without locks?

  - by Andrey

  This is pure just for interest question, any sort of questions are welcome. So is it possible to create thread-safe collections without any locks? By locks I mean any thread synchronization mechanisms, including Mutex, Semaphore, and even Interlocked, all of them. Is it possible at user level, without calling system functions? Ok, may be implementation is not effective, i am interested in theoretical possibility. If not what is the minimum means to do it? EDIT: Why immutable collections don't work. This of class Stack with methods Add that returns another Stack. Now here is program: Stack stack = new ...; ThreadedMethod() { loop { //Do the loop stack = stack.Add(element); } } this expression stack = stack.Add(element) is not atomic, and you can overwrite new stack from other thread. Thanks, Andrey

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• Why must "stride" in the System.Drawing.Bitmap constructor be a multiple of 4?

  - by Gorchestopher H

  I am writing an application that requires me to take a proprietary bitmap format (an MVTec Halcon HImage) and convert it into a System.Drawing.Bitmap in C#. The only proprietary functions given to me to help me do this involve me writing to file, except for the use of a "get pointer" function. This function is great, it gives me a pointer to the pixel data, the width, the height, and the type of the image. My issue is that when I create my System.Drawing.Bitmap using the constructor: new System.Drawing.Bitmap(width, height, stride, format, scan) I need to specify a "stride" that is a multiple of 4. This may be a problem as I am unsure what size bitmap my function will be hit with. Supposing I end up with a bitmap that is 111x111 pixels, I have no way to run this function other than adding a bogus column to my image or subtracting 3 columns. Is there a way I can sneak around this limitation?

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• Where does complexity bloat from?

  - by AareP

  Many of our design decisions are based on our gut feeling about how to avoid complexity and bloating. Some of our complexity-fears are true, we have plenty of painful experience on throwing away deprecated code. Other times we learn that some particular task isn't really that complex as we though it to be. We notice for example that upkeeping 3000 lines of code in one file isn't that difficult... or that using special purpose "dirty flags" isn't really bad OO practice... or that in some cases it's more convenient to have 50 variables in one class that have 5 different classes with shared responsibilities... One friend has even stated that adding functions to the program isn't really adding complexity to your system. So, what do you think, where does bloated complexity creep from? Is it variable count, function count, code line count, code line count per function, or something else?

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• How to create Master/Detail view with two datagrids in ColdFusion

  - by Maklar

  In Coldfusion, I have Master and Detail data that I need to display in two separate cfgrids; like the typical Customers/Orders scenario. My cfgrids are bound to cfc functions which populate the cfgrids. In my current dataset, only one Customer has Orders and when I click on this record in the Master datagrid the Detail datagrid displays the related records. But when I click on a record in the Master datagrid that has no related detail records, the Detail datagrid does not refresh but maintains display of the previous data. Also the search icon within the datagrid's control panel indicates it is searching for values rather than displaying the Refresh icon. Can you please show me how to establish Master and Detail cfgrids where I can see Orders of Customers as I navigate through the Master datagrid? Any and all help will be greatly appreciated! Maklar

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• Postback problem? Not getting data back from DB

  - by Jason Shultz

  I'm not getting back data from my DB like I'm expecting. I know that I can get data from the DB because I have other functions working. With this page, what I'm trying to do is the following: If no postback, then I would like it to echo "No Category Selected" If a category has been chosen, then I would like for it to get that data from the DB and show it on the page. I'm sure I can do this all in one view, I'm just not doing something right. Can someone help please? Pastebin: http://pastebin.com/AQqcvnAb

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• Container of shared_ptr's but iterate with raw pointers

  - by Sean Lynch

  I have a class that holds a list containing boost::shared_ptrs to objects of another class. The class member functions that give access to the elemets in the list return raw pointers. For consistency I'd also like to be able to iterate with raw pointers instead of shared_ptrs. So when I dereference the list iterator, I'd like to get raw pointer, not a shared_ptr. I assume I need to write a custom iterator for this. Is this correct? If so can someone point me in the right direction - I've never done this before.

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• How to organize code using an optional assembly reference?

  - by apoorv020

  I am working on a project and want to optionally use an assembly if available. This assembly is only available on WS 2008 R2, and my ideal product whould be a common binary for both computers with and without the assembly. However, I'm primarily developing on a Windows 7 machine, where I cannot install the assembly. How can I organize my code so that I can (with minimum changes) build my code on a machine without the assembly and secondly, how do I ensure that I call the assembly functions only when it is present. (NOTE : The only use of the optional assembly is to instantiate a class in the library and repeatedly call a (single) function of the class, which returns a boolean. The assembly is fsrmlib, which exposes advanced file system management operations on WS08R2.) I'm currently thinking of writing a wrapper class, which will always return true if the assembly is not present. Is this the right way to go about doing this?

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• Why isn't UTF-8 allowed as the "ANSI" code page?

  - by dan04

  The Windows _setmbcp function allows any valid code page... (except UTF-7 and UTF-8, which are not supported) OK, not supporting UTF-7 makes sense: Characters have non-unique representations and that introduces complexity and security risks. But why not UTF-8? As I understand it, the "ANSI" versions of the Windows API functions convert their arguments to UTF-16, call the equivalent "W" function, and convert any strings in the output to "ANSI". This is what I've been doing manually. So why can't Windows do it for me?

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• DLL/TLB in Java<->DCOM communication

  - by beermann

  I have to write an OpenOffice add-on (in Java) which communicates with DCOM server of some closed-source application. The major problem is that, I don't have any documentation about server's Interfaces . All I have is a VB/C++ SDK kit for the Application. SDK contain a library in dll and a bunch of *.tlb files. In SDK documentation there is an information, I can use java, but there is no example at all. I have read provided examples and it looks like all the communication wit DCOM goes through this dll. Is there a way to somehow import such dll/tlb functions def directly to java, bypass dll and comunicate with DCOM or I have to write a C++ wrapper(dll)? What is the best way to do it? Any hints are welcomed.

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• Using free function as pseudo-constructors to exploit template parameter deduction

  - by Poita_

  Is it a common pattern/idiom to use free functions as pseudo-constructors to avoid having to explicitly specify template parameters? For example, everyone knows about std::make_pair, which uses its parameters to deduce the pair types: template <class A, class B> std::pair<A, B> make_pair(A a, B b) { return std::pair<A, B>(a, b); } // This allows you to call make_pair(1, 2), // instead of having to type pair<int, int>(1, 2) // as you can't get type deduction from the constructor. I find myself using this quite often, so I was just wondering if many other people use it, and if there is a name for this pattern?

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• Type patterns and generic classes in Haskell

  - by finnsson

  I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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• Implementing password hashing/salting algorithm from crackstation.net

  - by Mason240

  I am trying to implement a password hashing/salting algorithm from crackstation.net, but I am unsure how implement it. Storing the password upon user registration seems to be as simple as passing the password into create_hash(). $password = create_hash($_POST['Password']; I'm not following how to validate upon user login. validate_password($password, $good_hash) returns either true or false, and takes $password as parameter, so it seems like a no brainer except for the second parameter $good_hash. Where does this param come from? It is my understanding that password is turned into a hash value every time its used, and that the hash value is what is stored and compared. So why would I have both the $password and $good_hash values? Quick overview of the functions: function create_hash($password){ calls pbkdf2() } function validate_password($password, $good_hash){ calls pbkdf2() calls slow_equals() } function slow_equals($a, $b){ } function pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false){ } Of course a different, better method for this would also be just as helpful. Thank you

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• Flex - How do I get the absolute X and Y coordinate including HTML offset?

  - by Mauricio

  Hey everyone, I am calling a JS function through the ExternalInterface using Flex which requires the absolute X and Y coordinates to create a pop-up menu. The Flex application is displayed on the center of an HTML page, therefore there is an HTML X and Y offset to consider. I have tried using the LocalToGlobal and ContentToGlobal functions, but these are just giving me the X and Y coordinates relative to the Flex application, it is not considering the HTML X and Y offset of having the Flex app in the center of the page or varying different screen resolutions. Is the best approach to retrieve the HTML X and Y offset using JavaScript? Is there a Flex function I can use that provides the absolute X and Y coordinates based on the HTML page? Thanks!

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• How do I pass custom variables to javascript events?

  - by RoboShop

  I have a user control with a javascript function which references some controls within the user control. This user control works perfectly when there is only one instance of it, but I'm now building a page where I have two instances of the user control. In IE7, it works fine, but in FireFox, it is getting confused that there is two functions of the exact same name and signature. So on UserControl1, it'll be running the function in UserControl2 and modifying that content. I'm thinking my best solution would be to pass the clientID of the components I need TO the function instead of just directly referencing it in the function. How would I do that? The signature of the javascript function is like this function nodeClicking(sender, args) and I'm calling it in an event like this <telerik:RadTreeView runat="server" ID="OrgUnitTreeView" OnInit="TreeViewLoad" OnClientNodeClicking="**nodeClicking**" EnableViewState="true" DataTextField = "OrganisationUnitName" DataValueField = "OrganisationUnitCode" DataFieldParentID = "ParentOrganisationUnitCode" DataFieldID = "OrganisationUnitCode"> How do I add extra variables to the function signature.

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• Obtaining references to function objects on the execution stack from the frame object?

  - by Marcin

  Given the output of inspect.stack(), is it possible to get the function objects from anywhere from the stack frame and call these? If so, how? (I already know how to get the names of the functions.) Here is what I'm getting at: Let's say I'm a function and I'm trying to determine if my caller is a generator or a regular function? I need to call inspect.isgeneratorfunction() on the function object. And how do you figure out who called you? inspect.stack(), right? So if I can somehow put those together, I'll have the answer to my question. Perhaps there is an easier way to do this?

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• Is it possible that __doPostBack() would ever send a GET request?

  - by Galilyou

  I'm having a problem with telerik RadGrid, I want to enable multiple row selection. I also want to go to the server whenever a row is selected or deselected. I created a javascript function to handle the Grid's client side events (OnRowSelected, and OnRowDeSelected). The functions look like this: function onOperationRowSelected(sender, eventArgs) { __doPostBack("<%=myControl.ClientID %>", "rowSelected:" + eventArgs.get_itemIndexHierarchical()); } The other function is very similar, the only difference is that it sends the string "rowDeselcted" instead of "rowSelected". On Page_Load I check to see if the request is a Post request using "IsPostBack" and if so, I check to see if it's a rowSelected or rowdeselected. My problem is when I select a first raw on my grid, a Post request happens (which is expected), however, when I select the second row, a GET request is issued, which (obviously) will result in IsPostBack returning false. What am I missing here?

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• Naming Optional Parameters in VSB

  - by SteveNeedsSheetNames

  In Visual Basic, I have Functions with a lot of Optional arguments. I would like to be able to pass just a few of these Optional arguments to a Function without having to use numerous commas and spaces to get to the ones I want. Somewhere I saw a way to name params such as OptVar:=val, but that does not seem to work. Just wondering if there is a way to do this. This would help readability. Thanks in advance for the replies.

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• PHP pass associative array from one function to another wihle keeping keys intact

  - by veronica

  I have two functions and one array function A { $segments = array(); $segments['word']=$var1; $segments['word2']=$var2; $segments['word3']=$var3; return $segments; } function B { $someVar=$segments['word']; $someVar1=$segments['word']; $someVar2=$segments['word']; $vars['other_stuff']... return $vars; } but I am not passing $segments['word']...word3'] to the second function. I am passing $segments[0]; $segments[1]; etc... How can I pass the keys to second function $segments['word'] $segments['word1'] $segments['word2'] Thank you,

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• How do you make an in-place construction of a struct casted to array compile in Visual C++ 2008?

  - by Irwin1138

  I'm working with quite a big codebase which compiles fine in linux but vc++ 2008 spits errors. The problem code goes like this: Declaration: typedef float vec_t; typedef vec_t vec2_t[2]; The codebase is littered with in-place construction like this one: (vec2_t){0, divs} Or more complex: (vec2_t){ 1/(float)Vid_GetScreenW(), 1/(float)Vid_GetScreenH()} As far as I know, this code constructs a struct, then converts it to an array and passes the address to the function. I personally never used in-place construction like this so I have no clue how to make this one work. I don't maintain the linux build, only the windows one. And I can't get it to compile. Is there some switch, some macro to make vc++ compile it? Maybe there is a similar nifty way to construct those arrays and pass them to the functions in-place that compiles just fine in vc++?

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• In C, how do you capture a group with regex?

  - by Sylvain

  Hi, I'm trying to extract a string from another using regex. I'm using the POSIX regex functions (regcomp, regexec ...), and I fail at capturing a group ... For instance, let the pattern be something as simple as "MAIL FROM:<(.*)>" (with REG_EXTENDED cflags) I want to capture everything between '<' and '' My problem is that regmatch_t gives me the boundaries of the whole pattern (MAIL FROM:<...) instead of just what's between the parenthesis ... What am I missing ? Thanks in advance,

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• SEARCHING AND REPLACING BRACKETS IN A STRING IN ORACLE 10G

  - by Tunde

  hello, Thanks as usual for your prompt and kind suggestions. i am currently developing a function that is meant to execute dynamically created SQL statements. this is done by concatenating the columns and fetching them via cursors. the problem is that when there is a function with a comma between its arguments, the concat concatenates the contents of the functions inclusive. Is it possible to skip contents of every bracket found in a string using REGEXP_SUBTR or REGEXP_REPLACE? Many thanks for the anticipated response.

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• Pros and Cons of Different macro function / inline methods in C

  - by Robert S. Barnes

  According to the C FAQ, there are basically 3 practical methods for "inlining" code in C: #define MACRO(arg1, arg2) do { \ /* declarations */ \ stmt1; \ stmt2; \ /* ... */ \ } while(0) /* (no trailing ; ) */ or #define FUNC(arg1, arg2) (expr1, expr2, expr3) To clarify this one, the arguments are used in the expressions, and the comma operator returns the value of the last expression. or using the inline declaration which is supported as an extension to gcc and in the c99 standard. The do { ... } while (0) method is widely used in the Linux kernel, but I haven't encountered the other two methods very often if at all. I'm referring specifically to multi-statement "functions", not single statement ones like MAX or MIN. What are the pros and cons of each method, and why would you choose one over the other in various situations?

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