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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • C++ Passing `this` into method by reference

    - by David
    I have a class constructor that expects a reference to another class object to be passed in as an argument. I understand that references are preferable to pointers when no pointer arithmetic will be performed or when a null value will not exist. This is the header declaration of the constructor: class MixerLine { private: MIXERLINE _mixerLine; public: MixerLine(const MixerDevice& const parentMixer, DWORD destinationIndex); ~MixerLine(); } This is the code that calls the constructor (MixerDevice.cpp): void MixerDevice::enumerateLines() { DWORD numLines = getDestinationCount(); for(DWORD i=0;i<numLines;i++) { MixerLine mixerLine( this, i ); // other code here removed } } Compilation of MixerDevice.cpp fails with this error: Error 3 error C2664: 'MixerLine::MixerLine(const MixerDevice &,DWORD)' : cannot convert parameter 1 from 'MixerDevice *const ' to 'const MixerDevice &' But I thought pointer values could be assigned to pointers, e.g. Foo* foo = new Foo(); Foo& bar = foo;

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  • Should I use a hosted version of JQuery? Which one?

    - by ataylor
    Should I use a local copy of jquery, or should I link to a copy provided by Google or Microsoft? I'm primarily concerned about speed. I've heard that just pulling content from other domains can have performance advantages related to how browsers limit connections. In particular, has anyone benchmarked the speed and latency of Google vs. Microsoft vs. local? Also, do I have to agree to any conditions or licenses to link from a third-party?

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  • Is there a way to use template specialization to separate new from new[]?

    - by Marlon
    I have an auto pointer class and in the constructor I am passing in a pointer. I want to be able to separate new from new[] in the constructor so that I can properly call delete or delete[] in the destructor. Can this be done through template specialization? I don't want to have to pass in a boolean in the constructor. template <typename T> class MyAutoPtr { public: MyAutoPtr(T* aPtr); }; // in use: MyAutoPtr<int> ptr(new int); MyAutoPtr<int> ptr2(new int[10]);

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  • Why wont my while loop wont take new input (c++)

    - by Van
    I've written a program to get a string input from a user and parse it into tokens and move a robot according to the input. My problem is trying to issue more than one command. The code looks like: void Navigator::manualDrive() { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; while(true) { Navigator::parseInstruction(uinput); } } /* parseInstruction(char *c) -- parses cstring instructions received * and moves robot accordingly */ void Navigator::parseInstruction(char * c) { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; cout << "Enter your directions below: \n"; cin.ignore(); cin.getline (uinput, bufSize); token=strtok(uinput, delim); if(strcmp("forward", token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); Navigator::travel(inches); } if(strcmp("back",token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); double value = fabs(0.0735 * fabs(inches) - 0.0550); myRobot.backward(1/*speed*/, value/*time*/); } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("left",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnLeft(1/*speed*/, value/*time*/); } } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("right",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnRight(1/*speed*/, value/*time*/); } } if(strcmp("stop",token) == 0) { myRobot.motors(0,0); } } In the function manualDrive I have a while loop calling the function parseInstruction infinitely. The program outputs "Enter your directions below: " When I give the program instructions it executes them, and then it outputs "enter your directions below: " again and when I input my directions again it does not execute them and outputs "Enter your directions below: " instead. I'm sure this is a very simple fix I'm just very new to c++. So if you could please help me out and tell me why the program only takes the first set of directions. thanks

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  • Primary reasons why programming language runtimes use stacks?

    - by manuel aldana
    Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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  • Button (using <button> tag) does not display in Opera

    - by Tanveer Dewan
    On my website I am using the html 'button' tag but the button does not display when page is opened in Opera version 12.15. Works fine in chrome, firefox and IE. If you go to my cdn test site CDN Comparison u see cloudflare, incapsula and page speed images. below the three cdn images there's a button which does not display. It's supposted to be right above the 'Test and monitor image load speed of the top three Free CDN Service providers' sentence. please help. <button id="button" onclick="changeLink()">Test Another Image</button> I have not added any style to this tag using CSS

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  • Object initializers not working in List<T>.

    - by Jebli
    List<Car> oUpdateCar = new List<Car>(); oUpdateCar.Add(new Car()); oUpdateCar[0].name = "Color"; oUpdateCar[0].value = "red"; oUpdateCar.Add(new Car()); oUpdateCar[1].name = "Speed"; oUpdateCar[1].value = "200"; The above code is working but i want to initialize it when i create the list as below, List<Car> oUpdateCar = new List<Car> { new Car{ name = "Color"; value = "red";} new Car{ name = "Speed"; value = "200";} } The above code is not working. What am i missing. I am using c# .NET 2.0. Please help.

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  • What's the most effective way to interpolate between two colors? (pseudocode and bitwise ops expecte

    - by navand
    Making a Blackberry app, want a Gradient class. What's the most effective way (as in, speed and battery life) to interpolate two colors? Please be specific. // Java, of course int c1 = 0xFFAA0055 // color 1, ARGB int c2 = 0xFF00CCFF // color 2, ARGB float st = 0 // the current step in the interpolation, between 0 and 1 /* Help from here on. Should I separate each channel of each color, convert them to decimal and interpolate? Is there a simpler way? interpolatedChannel = red1+((red2-red1)*st) interpolatedChannel = interpolatedChannel.toString(16) ^ Is this the right thing to do? If speed and effectiveness is important in a mobile app, should I use bitwise operations? Help me! */

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  • Silencing GCC warnings when using an "Uncopyable" class

    - by Kazade
    I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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  • grdb not working variables

    - by stupid_idiot
    hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake? I see the problem, dunno how to fix it yet though. The thing is, for some reason the instruction pointer starts at 0x100 and all the segment registers at 0x1628. To address the instruction the used combination is i guess [cs:ip] (one of the segment registers and the instruction pointer for sure). The offset to var1 is 0x10 (probably because from the begining of the code it's the 0x10th byte in order), i tried to examine the memory and what i got was: 1628:100 8 bytes 1628:108 8 bytes 1628:110 <- wtf? (assume another 8 bytes) 1628:118 ... whatever tricks are there in the memory [cs:var1] points somewhere else than in my code, which is probably where the label .data would usually address ds.... probably.. i don't know what is supposed to be at 1628:10 ok, i found out what caused the assness and wasted me whole fuckin day. the behaviour described above is just correct, the code is fully functional. what i didn't know is that grdb debugger for some reason sets the begining address to 0x100... the sollution is to insert the directive ORG 0x100 on the first line and that's the whole thing. the code was working because instruction pointer has the right address to first instruction and goes one by one, but your assembler doesn't know what effective address will be your program stored at so it pretty much remains relative to first line of the code which means all the variables (if not using label for data section) will remain pointing as if it started at 0x0. which of course wouldn't work with DOS. and grdb apparently emulates some DOS features... sry for the language, thx everyone for effort, hope this will spare someone's time if having the same problem... heheh.. at least now i know the reason why to use .data section :))))

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  • Does Django tests run slower on the mac compared to linux?

    - by Thierry Lam
    I'm currently developing my Django projects on both: Mac OS X 10.5, 32 bit Ubuntu Server 9.10 64 bits (1 CPU, 512MB RAM) Both of the above OS are using: Python 2.6.4 Django 1.1.1 MySQL 5.1 Running 12 tests for one of my application take: Mac: 57.513s Linux: 30.935s EDIT: Mac Hardware Spec: MacBook Pro 2.2 GHz Intel Core 2 Duo 3GB RAM I'm running the Ubuntu OS on the same mac above through VMware Fusion 2.0.6. You might argue that Ubuntu Server 64 bits is faster but I have observed a similar speed difference on Ubuntu 8.10 32 bits desktop edition. Even if I turn off my linux VM and other mac applications, I still experience the slowness. Has anyone else experienced this Django test speed difference across those two OS?

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  • Mouse Wheel Scroll - How can I capture the time interval between start and stop of scrolling?

    - by Rahat
    Is there any way to capture the time interval between mouse wheel scroll start and stop? Actually I want to capture the interval between the scrolling start and stop when I very quickly scroll the mouse wheel. I have already looked at MouseWheel event but it don't fulfill my requirement. In senes that it always gives a value of Delta 120 or -120 but i want to call a function depending on the speed of the mouse scroll for example when i scroll the mouse normally i want to perform function 1 and when i scrolled the mouse very quickly i want to perform the function 2. In other words is there any way to distinguish between the mouse scroll high and normal speed. Any advice will be appreciated.

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  • For-Each and Pointers in Java

    - by John
    Ok, so I'm tyring to iterate through an ArrayList and remove a specefic element. However, I am having some trouble using the For-Each like structure. When I run the following code: ArrayList<String> arr = new ArrayList<String>(); //... fill with some values (doesn't really matter) for(String t : arr) { t = " some other value "; //hoping this would change the actual array } for(String t : arr) { System.out.println(t); //however, I still get the same array here } My question in, how can I make 't' a pointer to 'arr' so that I am able to change the values in a for-each loop? I know I could loop through the ArrayList using a different structure, but this one looks so clean and readable, it would just be nice to be able to make 't' a pointer. All comments are appreciated! Even if you say I should just suck it up and use a different construct.

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Inline function and calling cost in C

    - by Eonil
    I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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  • Configuring a html page from an original demo page

    - by Wold
    I forked into rainyday.js through github, an awesome javascript program made by maroslaw at this link: https://github.com/maroslaw/rainyday.js. Basically I tried taking his demo page and my own photo city.jpg and changed the applicable fields so that I could run it on my own site, but only the picture loads and the script itself doesn't start to run. I'm pretty new to html and javascript so I'm probably omitting something very simple, but here is the script for the demo code: <script src="rainyday.js"></script> <script> function getURLParameter(name) { return decodeURIComponent((new RegExp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search)||[,''])[1].replace(/\+/g, '%20'))||null; } function demo() { var image = document.getElementById('background'); image.onload = function () { var engine = null; var preset = getURLParameter('preset') || '1'; if (preset === '1') { engine = new RainyDay({ element: 'background', blur: 10, opacity: 1, fps: 30, speed: 30 }); engine.rain([ [1, 2, 8000] ]); engine.rain([ [3, 3, 0.88], [5, 5, 0.9], [6, 2, 1] ], 100); } else if (preset === '2') { engine = new RainyDay({ element: 'background', blur: 10, opacity: 1, fps: 30, speed: 30 }); engine.VARIABLE_GRAVITY_ANGLE = Math.PI / 8; engine.rain([ [0, 2, 0.5], [4, 4, 1] ], 50); } else if (preset === '3') { engine = new RainyDay({ element: 'background', blur: 10, opacity: 1, fps: 30, speed: 30 }); engine.trail = engine.TRAIL_SMUDGE; engine.rain([ [0, 2, 0.5], [4, 4, 1] ], 100); } }; image.crossOrigin = 'anonymous'; if (getURLParameter('imgur')) { image.src = 'http://i.imgur.com/' + getURLParameter('imgur') + '.jpg'; } else if (getURLParameter('img')) { image.src = getURLParameter('img') + '.jpg'; } var youtube = getURLParameter('youtube'); if (youtube) { var div = document.getElementById('sound'); var player = document.createElement('iframe'); player.frameborder = '0'; player.height = '1'; player.width = '1'; player.src = 'https://youtube.com/embed/' + youtube + '?autoplay=1&controls=0&showinfo=0&autohide=1&loop=1'; div.appendChild(player); } } </script> This is where I am naming my background and specifying the photo from within the directory. <body onload="demo();"> <div id="sound" style="z-index: -1;"></div> <div id="parent"> <img id='background' alt="background" src="city.jpg" /> </div> </body> The actual code for the whole entire rainyday.js script can be found here: https://github.com/maroslaw/rainyday.js/blob/master/rainyday.js Thanks in advance for any help and advice!

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • How to use the vtable to determine class type

    - by Alex Silverman
    I was recently on an interview for a position where C/C++ is the primary language and during one question I was told that it's possible to use the vtable to determine which class in a hierarchy a base pointer actually stores. So if, for example you have class A { public: A() {} virtual ~A() {} virtual void method1() {} }; class B : public A { public: B() {} virtual ~B() {} virtual void method1() {} }; and you instantiate A * pFoo = new B(), is it indeed possible to use the vtable to determine whether pFoo contains a pointer to an instance of A or B?

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  • Training new employees on undocumented code

    - by glowcoder
    Our company has a large codebase (2500+ classes/interfaces in just the core alone, many more in other projects) for our flagship software product. We've never really hired more than one developer at a time, so we don't have a real training process. We're going to be bringing in 2-5 more developers now, and probably more in the near future (to put things into perspective, we have 7 right now.) Obviously, we would like to get these guys up to speed as soon as possible. The catch - almost all of our classes (95%+) are completely undocumented. No javadoc, no design docs, basically completely undocumented. What strategies can we employ to bring the new developers up to speed? I'd like to consider situations that include the existing code getting documented, but it's possible management won't allow for the time to get that done, so I also must consider situations where that won't happen. Has anyone been there before? What worked well for you? Thanks!

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  • Somewhat newb question about assy and the heap.

    - by Eric M
    Ultimately I am just trying to figure out how to dynamically allocate heap memory from within assembly. If I call Linux sbrk() from assembly code, can I use the address returned as I would use an address of a statically (ie in the .data section of my program listing) declared chunk of memory? I know Linux uses the hardware MMU if present, so I am not sure if what sbrk returns is a 'raw' pointer to real RAM, or is it a cooked pointer to RAM that may be modified by Linux's VM system? I read this: How are sbrk/brk implemented in Linux?. I suspect I can not use the return value from sbrk() without worry: the MMU fault on access-non-allocated-address must cause the VM to alter the real location in RAM being addressed. Thus assy, not linked against libc or what-have-you, would not know the address has changed. Does this make sense, or am I out to lunch?

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  • template typename question

    - by stephenteh
    Hi, I have a problem with template and wondering is there a possible way to achieve what I wanted to do. Here is my question. template <typename T> class A { public: typedef T* pointer; typedef const pointer const_pointer; A() {} template <typename D> A(const D& d) { // how can I store the D type // so I can refer it later on // outside of this function } };

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