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  • a class function with if(this==NULL) test got compiled?

    - by James
    I saw this code snippet during our lab and it actually compiles in MSVC2008 and G++. void LinkList< class T ::Insert(T n) { if (this == NULL) // some code here } As far as I know the this must not be null since you cannot call a class functions in c++ if it wasn't instantiated. Is this a valid code? if so what's the reason behind and where it can be useful?

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  • Specializating a template function that takes a universal reference parameter

    - by David Stone
    How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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  • Core Location and speed measurements

    - by Krumelur
    Does anyone know if Core Location in the iPhone OS uses anything but simple vector math to calculate speed? I've read that the GPS system can provide speed measurements that can be accurate when position is not (I believe using the Doppler shifts of the signals). I've tried and failed to see if the iPhone does this. The question is basically, does this data contain information or is it just convenience functions, using (filtered?) location data?

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  • Numpy: Creating a complex array from 2 real ones?

    - by Duncan Tait
    I swear this should be so easy... Why is it not? :( In fact, I want to combine 2 parts of the same array to make a complex array: Data[:,:,:,0] , Data[:,:,:,1] These don't work: x = np.complex(Data[:,:,:,0], Data[:,:,:,1]) x = complex(Data[:,:,:,0], Data[:,:,:,1]) Am I missing something? Does numpy not like performing array functions on complex numbers? Here's the error: TypeError: only length-1 arrays can be converted to Python scalars Cheers

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  • Overloading new, delete in C++

    - by user265260
    i came across this line is stroustrup An operator function must either be a member or take at least one argument of a user-defined type (functions redefining the new and delete operators need not). Dont operator new and operator delete take an user defined type as one of their arguments? what does it mean, am i missing something here

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  • Mod_rewrite and redirects with training forward slash not working

    - by john williams
    I'm using the following lines of code in my .htaccess file to create redirects. The problem is, whenever I go to example.com/register/ it cant find the css files because it's looking for example.com/register/mycss.css instead of example.com/mycss.css. Redirect 301 register.php http://example.com/register RewriteRule ^register/?$ register.php How can I correct this? I'm new to any kind of htaccess/mod_rewrite functions so feel free to point me in the right direction if there are any other flaws.

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  • 3D plotting in Matlab

    - by Jill
    I'm using the subplot and then surf functions to generate images in 3D in Matlab. How do I get rid of the axes and axis' gridlines and change the color to all yellow or all green or something like that? Thanks.

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  • Find out why Xcode has decided to link to a particular library

    - by andygeers
    I'm using the Unity 3D engine to build an iPhone app, and when I go to generate my Xcode project for compilation, it includes a few fairly large libraries: Mono.Security.dll.s, System.dll.s, System.Core.dll.s, etc. I don't know if this question is really an Xcode question or a Unity question, but I'm trying to figure out why each of those libraries is being linked - which functions / classes are being referenced - ideally so that I can rewrite my code to remove as many of the dependencies as possible. Does anybody know a way to find this information out?

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  • output with "Private`" Content in Mathematica Package

    - by madalina
    Hello everyone, I am trying to solve the following implementation problem in Mathematica 7.0 for some days now and I do not understand exactly what is happening so I hope someone can give me some hints. I have 3 functions that I implemented in Mathematica in a source file with extension *.nb. They are working okay to all the examples. Now I want to put these functions into 3 different packages. So I created three different packages with extension .*m in which I put all the desired Mathematica function. An example in the "stereographic.m" package which contain the code: BeginPackage["stereographic`"] stereographic::usage="The package stereographic...." formEqs::usage="The function formEqs[complexBivPolyEqn..." makePoly::usage="The function makePoly[algebraicEqn] ..." getFixPolys::usage="The function..." milnorFibration::usage="The function..." Begin["Private`"] Share[]; formEqs[complex_,{m_,n_}]:=Block[{complexnew,complexnew1, realeq, imageq, expreal, expimag, polyrealF, polyimagF,s,t,u,v,a,b,c,epsilon,x,y,z}, complexnew:=complex/.{m->s+I*t,n->u+I*v}; complexnew1:=complexnew/.{s->(2 a epsilon)/(1+a^2+b^2+c^2),t->(2 b epsilon)/(1+a^2+b^2+c^2),u->(2 c epsilon)/(1+a^2+b^2+c^2),v->(- epsilon+a^2 epsilon+b^2 epsilon+c^2 epsilon)/(1+a^2+b^2+c^2)}; realeq:=ComplexExpand[Re[complexnew1]]; imageq:=ComplexExpand[Im[complexnew1]]; expreal:=makePoly[realeq]; expimag:=makePoly[imageq]; polyrealF:=expreal/.{a->x,b->y,c->z}; polyimagF:=expimag/.{a->x,b->y,c->z}; {polyrealF,polyimagF} ] End[] EndPackage[] Now to test the function I load the package Needs["stereographic`"] everything is okay. But when I test the function for example with formEqs[x^2-y^2,{x,y}] I get the following ouput: {Private`epsilon^2 + 2 Private`x^2 Private`epsilon^2 + Private`x^4 Private`epsilon^2 - 6 Private`y^2 Private`epsilon^2 + 2 Private`x^2 Private`y^2 Private`epsilon^2 + Private`y^4 Private`epsilon^2 - 6 Private`z^2 Private`epsilon^2 + 2 Private`x^2 Private`z^2 Private`epsilon^2 + 2 Private`y^2 Private`z^2 Private`epsilon^2 + Private`z^4 Private`epsilon^2, 8 Private`x Private`y Private`epsilon^2 + 4 Private`z Private`epsilon^2 - 4 Private`x^2 Private`z Private`epsilon^2 - 4 Private`y^2 Private`z Private`epsilon^2 - 4 Private`z^3 Private`epsilon^2} Of course I do not understand why Private` appears in front of any local variable which I returned in the final result. I would want not to have this Private` in the computed output. Any idea or better explanations which could indicate me why this happens? Thank you very much for your help. Best wishes, madalina

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  • How to combine query strings in PHP

    - by incrediman
    Given a url, and a query string, how can I get the url resulting from the combination of the query string with the url? I'm looking for functionality similar to .htaccess's qsa. I realize this would be fairly trivial to implement completely by hand, however are there built-in functions that deal with query strings which could either simplify or completely solve this? Example input/result sets: Url="http://www.example.com/index.php/page?a=1" QS ="?b=2" Result="http://www.example.com/index.php/page?a=1&b=2" - Url="page.php" QS ="?b=2" Result="page.php?b=2"

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  • mysql_query -- question about results "location"

    - by Andrew Heath
    Forgive me if this is a particularly stupid question! mysql_query($query) returns a boolean, but you can also assign it to a variable $results = mysql_query($query) and then use the other mysql_ functions to extract data. Out of curiosity, how does mysq_query($query) act as both a boolean and a data container at the same time? What's happening "under the hood" during these steps? (yes, I am a n00b..., please be kind!)

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  • OpenCV performance in different languages

    - by h0b0
    I'm doing some prototyping with OpenCV for a hobby project involving processing of real time camera data. I wonder if it is worth the effort to reimplement this in C or C++ when I have it all figured out or if no significant performance boost can be expected. The program basically chains OpenCV functions, so the main part of the work should be done in native code anyway.

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  • In flex how do I pass data retrieved from a remote object service to a modules interface?

    - by Dan G
    I found at this Adobe tutorial a nice "RemoteService" class that creates a RemoteObject and contains the functions for handling the result and fault events. If I wanted to use this approach, how could I pass the data from the result handler to interfaces that modules from the main application could use? I could put the RemoteService/RemoteObject in the modules, but (in my opinion- and I could be wrong) the best design seems to be using the remote calls in the main app and passing the data along to the modules.

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  • Problem with the POSIX module

    - by planetp
    After moving my mod_perl site from Linux hosting to FreeBSD, I have this error in the logfile: Your vendor has not defined POSIX macro SIGRTMIN, used at ../../lib/POSIX.pm (autosplit into ../../lib/auto/POSIX/SigRt/_init.al) line 993\n The script just imports POSIX and utilizes some functions (ceil, etc) How can I solve this issue ?

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  • Is there a full REPL for Erlang?

    - by Gabriel Cuvillier
    Is there a way to have a full interpreter in Erlang, not just a "shell". Since it is a dynamic language, not being able to define named functions in the interpreter is a little bit disappointing... I suspect that it is because compilation units (modules) must be explicitly compiled for their execution by the VM, but maybe a REPL acting as a dynamic/recompilable module exist?

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  • How do you avoid an invalid search space in a genetic algorithm?

    - by Dave
    I am developing a GA for a school project and I've noticed that upon evaluating my functions for fitness, an individual is equivalent to its inverse. For example, the set (1, 1, -1, 1) is equivalent to (-1, -1, 1, -1). To shrink my search space and reach a solution more efficiently, how can I avoid my crossovers from searching in this second half of the search space?

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  • How do you return a pointer to a base class with a virtual function?

    - by Nick Sweet
    I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Element.h" template <class T> class Vector: public Element<T> { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y = 0, const T& z =0); Vector(const Vector& u); ... //operations Element<T>& plus(const Element<T>& v) const; Element<T>& minus(const Element<T>& v) const; ... }; //sum template <class T> Element<T>& Vector<T>::plus(const Element<T>& v) const { Element<T>* ret = new Vector((x + v.x), (y + v.y), (z + v.z)); return *ret; } //difference template <class T> Element<T>& Vector<T>::minus(const Element<T>& v) const { Vector<T>* ret = new Vector((x - v.x), (y - v.y), (z - v.z)); return *ret; } but I always get error: 'const class Element' has no member named 'getx' So, can I define my virtual functions to take Vector& as an argument instead, or is there a way for me to access the data members of Vector through a pointer to Element? I'm still fairly new to inheritance polymorphism, fyi.

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  • How to Convert Boolean to String

    - by tag
    I have a boolean variable which I want to convert to a string $res = true; I need it the converted value to also be in the format "true" "false" not "0" "1" $converted_res = "true"; $converted_res = "false"; I've tried: $converted_res = string($res); $converted_res = String($res); but it tells me string and String are not recognized functions. How do I convert this boolean to a string in the format "true" or "false" in php?

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  • Can an algorithmic process ever give true random numbers ?

    - by Arkapravo
    I have worked with random functions in python,ruby, MATLAB, Bash and Java. Nearly every programming language has a function to generate Random numbers. However, these apparently random sequences are termed as pseudo-random number sequences as the generation follows a deterministic approach, and the sequence seems to repeat (usually with a very large period). My question, can an algorithmic/programming process ever yield true random numbers ? The questions probably is more of theoretical computer science than just programming !

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  • need a project design tool

    - by santosh
    I am looking for simple and easy to use tools through which I can get project's visual picture of folder/file tree stucture , its classes, functions and objects, relations between classes and files.

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  • Dynamic content doesn't work when loaded with ajax

    - by Wurlitzer
    I'm trying to load some dynamic content after the user has logged in, using $.ajax, like so: $.ajax({ url: "functions.php", type: "GET", data: login_info, datatype: 'html', async: false, success: function (response) { $('#main').html(response); } }); The problem is, that some events don't work, when loaded this way. I fixed the buttons with the .live() method, but a sortable list for example, doesn't work. How can I somehow refresh the DOM, and let jquery know of these new added elements? Thanks!

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  • What is a de-compiler how does it work?

    - by thyrgle
    So is a decompiler really a thing that gives gives the source of a compiled/interpreted piece of code? Because to me that sounds impossible. How would you get the names of the functions, variables, classes, etc if it is compiled. Or am I misinterpreting the definition? How does it work? And what is the general principal behind making one?

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  • adding javascript events to freemind maps

    - by pri_dev
    I have created freemind maps using the tool, right now in the process of integrating the map with my web application. I have some questions on the usage of freemind maps 1) Instead of using the freemindbrowser.html and the jar file to integrate a map with a website/ web app, can we do an export to Javascript from the tool and then integrate that exported file (.html) with the web site? 2) I want to be able to add javascript functions on events like node click, how do I do that? Thanks in Advance

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  • How to test my GAE site for performance

    - by Sergey Basharov
    I am building a GAE site that uses AJAX/JSON for almost all its tasks including building the UI elements, all interactions and client-server requests. What is a good way to test it for highloads so that I could have some statistics about how much resources 1000 average users per some period of time would take. I think I can create some Python functions for this purpose. What can you advise? Thanks.

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