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  • C++ get method - returning by value or by reference

    - by HardCoder1986
    Hello! I've go a very simple question, but unfortunately I can't figure the answer myself. Suppose I've got some data structure that holds settings and acts like a settings map. I have a GetValue(const std::string& name) method, that returns the corresponding value. Now I'm trying to figure out - what kind of return-value approach would be better. The obvious one means making my method act like std::string GetValue(const std::string& name) and return a copy of the object and rely on RVO in performance meanings. The other one would mean making two methods std::string& GetValue(...) const std::string& GetValue(...) const which generally means duplicating code or using some evil constant casts to use one of these routines twice. #Q What would be your choice in this kind of situation and why?

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  • Type hinting and optional attributes in PHP

    - by Álvaro G. Vicario
    I have a class method that deals with dates: public function setAvailability(DateTime $start, DateTime $end){ } Since item availability can have lower limit, upper limit, both or none, I'd like to make setAvailability() accept NULL values as well. However, the NULL constant violates the type hinting: $foo->setAvailability(NULL, $end); triggers: Catchable fatal error: Argument 1 passed to Foo::setAvailability() must be an instance of DateTime, null given And, as far as I know, I cannot have a DateTime instance with no value. (Can I?) For a reason I cannot grasp, this seems to work: public function setAvailability(DateTime $start=NULL, DateTime $end=NULL){ } ... $foo->setAvailability(NULL, $end); But it looks like a hack that works by pure chance. How would you deal with unset dates in PHP classes?

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  • Calculating the angle between two points

    - by kingrichard2005
    I'm currently developing a simple 2D game for Android. I have a stationary object that's situated in the center of the screen and I'm trying to get that object to rotate and point to the area on the screen that the user touches. I have the constant coordinates that represent the center of the screen and I can get the coordinates of the point that the user taps on. I'm using the formula outlined in this forum: How to get angle between two points? -It says as follows "If you want the the angle between the line defined by these two points and the horizontal axis: double angle = atan2(y2 - y1, x2 - x1) * 180 / PI;". -I implemented this, but I think the fact the I'm working in screen coordinates is causing a miscalculation, since the Y-coordinate is reversed. I'm not sure if this is the right way to go about it, any other thoughts or suggestions are appreciated.

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  • Which parallel sorting algorithm has the best average case performance?

    - by Craig P. Motlin
    Sorting takes O(n log n) in the serial case. If we have O(n) processors we would hope for a linear speedup. O(log n) parallel algorithms exist but they have a very high constant. They also aren't applicable on commodity hardware which doesn't have anywhere near O(n) processors. With p processors, reasonable algorithms should take O(n/p log n/p) time. In the serial case, quick sort has the best runtime complexity on average. A parallel quick sort algorithm is easy to implement (see here and here). However it doesn't perform well since the very first step is to partition the whole collection on a single core. I have found information on many parallel sort algorithms but so far I have not seen anything pointing to a clear winner. I'm looking to sort lists of 1 million to 100 million elements in a JVM language running on 8 to 32 cores.

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  • Calling some functions before main in C

    - by minjang
    I'd like to do some stuffs before main function. I have multiple source files. In each file, there is some work that needs to be done before main. It was no problem in C++, but problematic with C. In C++, this can be done by two ways: Exploiting a constructor of a global class/struct. Calling a function to a global variable For example, static const int __register_dummy_ = __AddRegisterMetaInfo(...); However, in C, either ways is impossible. Obviously, there is no constructor. So, the first option is inherently impossible. I thought that the second option would be possible, but not compiled in C (I tested only with Visual C++. It gives C2099.). C only allows a constant to a non-automatic variable. Is there any way to call some functions before main?

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  • Multiple key map in c++

    - by Morgan
    Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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  • What is the cost of memory access?

    - by Jurily
    We like to think that a memory access is fast and constant, but on modern architectures/OSes, that's not necessarily true. Consider the following C code: int i = 34; int *p = &i; // do something that may or may not involve i and p {...} // 3 days later: *p = 643; What is the estimated cost of this last assignment in CPU instructions, if i is in L1 cache, i is in L2 cache, i is in L3 cache, i is in RAM proper, i is paged out to an SSD disk, i is paged out to a traditional disk? Where else can i be? Of course the numbers are not absolute, but I'm only interested in orders of magnitude. I tried searching the webs, but Google did not bless me this time.

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  • Is there a way to create my own "push pins" for a image without using Google Maps API?

    - by Charlie
    I am interested in working with friends via the internet on a fantasy world map. One of the things I want to do is host an image of the map online and allow us to insert push pins into the image that would then be associated with infoboxes. I don't want to resort to using the Google Map APIs mainly because this is something I want to just share among friends and not publicly. Terms of usage for the APIs state we would need to make the implementation available for everyone. This seems simple enough yet I've no idea how to do this. I looked into image maps, but that requires constant updates to the html markup itself. I just want to insert/delete/edit pushpins and infoboxes on the image and through our site itself. Can someone help me get started?

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  • Stuck on solving the Minimal Spanning Tree problem.

    - by kunjaan
    I have reduced my problem to finding the minimal spanning tree in the graph. But I want to have one more constraint which is that the total degree for each vertex shouldnt exceed a certain constant factor. How do I model my problem? Is MST the wrong path? Do you know any algorithms that will help me? One more problem: My graph has duplicate edge weights so is there a way to count the number of unique MSTs? Are there algorithms that do this? Thank You. Edit: By degree, I mean the total number of edges connecting the vertex. By duplicate edge weight I mean that two edges have the same weight.

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  • Wireshark Display Filter protocol==TLSV1? (and PacketLength)

    - by NealWalters
    What would the filter expression be to just select the protocols where the protocol = TLSV1? Something obvious like protocol == "TLSV1" or TCP.protocol == "TLSV1" is apparently not the right way. ip.proto == "TLSV1" says "ip.proto cannot accept strings as values" Update - additional tips: Another great but hidden search is on PacketLength: You can add packet length to your display by clicking "Edit Preferences" (menu or icon), and adding the PacketLength as a new column, but to filter on it you have to use the more cryptic: frame.len == ### where ### is your desired number. We were using this to determine how many packets had been sent and/or received, when you filter, the status-bar at the bottom of the screen shows the number of items matching the filter.

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  • php script to generate checksum from md5

    - by sumit
    In order to calculate the checksum i need following things. these parameters are concatenated in a constant (no spaces) string made up of the values of the following parameters in the exact order listed below: o Secret Key o Merchant id o Currency o Total amount o Item list (item_name_1, Item_amount_1, item_quantity_1 to item_name_N, Item_amount_N, item_quantity_N) o Timestamp e.g In that case the string befor hash will be: pLAZdfhdfdNh57583USD69.99Tier2 item69.9912010-06-14.14:34:33 And using the MD5 hash function the result is: ghvsaf764t3w784tbjkegbjhdbgf i want to know how can i create a php script that will call md5 hash function with the inputs given above and based on that it will generate the hash function value that will be the checksum value for my coding..

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  • Haskell: foldl' accumulator parameter

    - by Clinton
    I've been asking a few questions about strictness, but I think I've missed the mark before. Hopefully this is more precise. Lets say we have: n = 1000000 f z = foldl' (\(x1, x2) y -> (x1 + y, y - x2)) z [1..n] Without changing f, what should I set z = ... So that f z does not overflow the stack? (i.e. runs in constant space regardless of the size of n) Its okay if the answer requires GHC extensions. My first thought is to define: g (a1, a2) = (!a1, !a2) and then z = g (0, 0) But I don't think g is valid Haskell.

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  • CUDA Global Memory, Where is it?

    - by gamerx
    I understand that in CUDA's memory hierachy, we have things like shared memory, texture memory, constant memory, registers and of course the global memory which we allocate using cudaMalloc(). I've been searching through whatever documentations I can find but I have yet to come across any that explicitly explains what is the global memory. I believe that the global memory allocated is on the GDDR of graphics card itself and not the RAM that is shared with the CPU since one of the documentations did state that the pointer cannot be dereferenced by the host side. Am I right?

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  • C++ static virtual members?

    - by cvb
    Is it possible in C++ to have a member function that is both static and virtual? Apperantly, there isn't a straight-forward way to do it (static virtual member(); is a complie error), but at least a way to acheive the same effect? I.E: struct Object { struct TypeInformation; static virtual const TypeInformation &GetTypeInformation() const; }; struct SomeObject : public Object { static virtual const TypeInformation &GetTypeInformation() const; }; It makes sence to use GetTypeInformation() both on an instance (object->GetTypeInformation()) and on a class (SomeObject::GetTypeInformation()), which can be useful for comparsions and vital for templates. The only ways I can think of involves writing two functions / a function and a constant, per class, or use macros. Any other solutions?

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  • How to research unmanaged memory leaks in .NET?

    - by Brandon
    I have a WCF service running over MSMQ. Memory gradually increases over time, indicating that there is some sort of memory leak. I ran the service locally and monitored some counters using PerfMon. Total CLR memory managed heap bytes remains relatively constant, while the process' private bytes increases over time. This leads me to believe that there is some sort of unmanaged memory leak. Assuming that unmanaged memory leak is the issue, how do I address the issue? Are there any tools I could use to give me hints as to what is causing the unmanaged memory leak? Also, all my service is doing is reading from the transactional queue and writing to a database, all as part of a DTC transaction (handled under the hood by requiring a transaction on the service contract). I am not doing anything explicitly with COM or DllImports. Thanks in advance!

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  • Hide Adsense on localhost

    - by collimarco
    I have a site built in Ruby On Rails which has many ads in different templates and views. It is hard to actualy remove each ad between tests and deployments. I don't know whether Google approves many impressions (even if without clicks) on localhost. How do you deal with this issue? Maybe it is a good solution to set a variable/constant available everywere to enable/disable ads easily. Do you think it is a good solution? If so, how do I declare a global variable for views?

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  • Why operator= returns reference not const reference

    - by outmind
    The original question is related to overloading operator= and I like to share my findings as it was nontrivial for me to find them. I cannot imagine reasonable example to use (a=b) as lvalue. With the help of IRC and google I've found the next article: http://msdn.microsoft.com/en-us/magazine/cc301415.aspx it provides two examples. (a=b)=c f(T& ); f(a=b) but both a bit not good, as first violate associativity and I believe that it is bad practice. The second one give me the same feeling. Could you provide more good examples why it should be non constant?

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  • Is there a way to redirect certain URLs to specific web browsers in Linux?

    - by jraxxo
    I'm using Chrome as my default browser in Ubuntu 12.10. I need to use Firefox for business purposes (certain websites pertaining to my work only work with Firefox). Is there a way to force Ubuntu to use Firefox for certain types of URLs (maybe as defined by a regular expression) while maintaining Chrome as my default browser for all my other tasks? Perhaps as a shell script running in the background? I'd like this to work system-wide, covering links from Chrome itself as well as PDFs/ODTs, etc. I have searched for solutions, but I couldn't find anything besides OpenWith, a Firefox extension which adds a button to open certain links in other browsers which would again require me to open Firefox beforehand, which does not help me at all. Does anyone have any ideas? Something like Choosy for Linux?

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  • a newbie gcc compiler and c language question

    - by dydx
    Hi, when I'm trying to compile my c program it gives me this error warning: integer constant is too large for 'long' type which refers to these lines int barcode, a, b, c; scanf("%d", &barcode); a = barcode / 1000000000000; b = barcode / 100000000000 % 10; c = barcode / 10000000000 % 10; and the rest is fine. I know I'm not supposed to use int for such a large number, any suggestions on what I should use? if I replace int with double what should the '%d' part be replaced with then?

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  • Simple Java math operations

    - by user1730056
    I'm making a BMI calculator that doesn't seem to be working. The math operations work if i just do something like w/h, but once i had the brackets, it returns an error. If i change the variables w and h and use a constant number, the operation works. Another problem is that although i'm making result a double, it seems to be rounding to the nearest int. Could someone tell me what I'm doing wrong here? public class ass10 { public static void main(String[] args) { bmi(223,100); } public static bmi(int w, int h){ double result; result = (w/(h*h))*703 System.out.println(result) } }

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  • NameError on accessing ancestor constants when using Class.new?

    - by PDG
    To my current knowledge Ruby classes defined with Class.new should not differ from classes created with the class keyword. Then why do following classes B and C behave differently? class A TEST = 'A' def test TEST end end class B < A def test TEST end end C = Class.new(A) { def test TEST end } puts 'A: ' + A.new.test # => "A: A" puts 'B: ' + B.new.test # => "B: A" puts 'C: ' + C.new.test # => uninitialized constant TEST (NameError) Tested with ruby 1.9.3p327 and ruby 1.8.7p358.

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  • Computer Software Needed

    - by captfrankie
    A friend started my website with Frontpage 2000 in Oct04. I used it until 09 and started to use Kompozer. I am starting to have difficulty updating my picture pages. Some pictures never show up or show up as X. I'm not sure what the problem is. I haven't been able to figure out how to upload files to Filezilla either. Is there a software program similar to Frontpage and Kompozer that will allow me to do weekly updates/addition to my picture pages without recreating the whole page? I dabbled with Web Builder 8-Easy WebEditor-Expression Web and Pagebreeze.

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  • Singly-Linked Lists insert_back and isIncreasing

    - by rezivor
    I just finished writing a program that I can add, remove or print objects to a list, but I am having difficulty implementing two more functions that is insert_back, which inserts a value to the end of a list. Also,I have to modify the representation of a List and alter whatever methods are necessary to make insert_back run in constant time: O(1). This new operation should have the signature: void List::insert_back( const Object& data ); Also, isIncreasing, For example, for a list containing head-() (11) (8) (15) (3), isIncreasing() should return false. However, it would return true when working on a list containing head- () (7) (9) (15). This new operation should have the signature: bool List::isIncreasing() const; Thank you

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  • Arrange 0's & 1's in a array

    - by Ganesh M
    This is one of an interview question which I had recently. I would like to know others perception of approach for this problem. Question: You are given a structure which holds an employee details with two elements as int Deptartment and string Name. struct Employee { string Name; int Dept; } You are given details of N Employees among which there are N/2 employees Dept are 0's and N/2 employees dept are 1's arranged in some random order. You need to sort the employee details based on their Dept value and it should be stable i.e., the order of 1s and 0s in the original record should be maintained. For example, given the following sample data: Name Dept X1 0 X2 1 X3 0 X4 1 X5 0 after sorting the result should be: Name Dept X2 1 X4 1 X1 0 X3 0 X5 0 The algorithm should be stable and the complexity should be o(N), with constant space for additional variables (which means sorting should be done in-place).

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  • modifying constants in objective c during run time

    - by moshikafya
    I am trying to solve the following problem. I have the following constants in my header file: #define PREFS_MY_CONSTANT_1 @"bla1" #define PREFS_MY_CONSTANT_2 @"bla2" #define PREFS_MY_CONSTANT_3 @"bla3" ... In one of my functions, I'd like to print to the UIbutton one of those strings based on user input, so say the user inputs '1', i would show bla1. Instead of creating a huge switch (i have 100 of those), I am looking for a way to combine the constant with the variable holding the user input, so something like that ideally: NSInteger input; [button setTitle:PREFS_MY_CONSTANT_{$input} forState: UIControlStateNormal]; Is something like that possible? what would be the best way to solve this?

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