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• How to deal with seniors' bad coding style/practices?

  - by KaluSingh Gabbar

  I am new to work but the company I work in hires a lot of non-comp-science people who are smart enough to get the work done (complex) but lack the style and practices that should help other people read their code. For example they adopt C++ but still use C-like 3 page functions which drives new folks nuts when they try to read that. Also we feel very risky changing it as it's never easy to be sure we are not breaking something. Now, I am involved in the project with these guys and I can't change the entire code base myself or design so that code looks good, what can I do in this situation? PS we actually have 3 page functions & because we do not have a concept of design, all we can do is assume what they might have thought as there is no way to know why is it designed the way it is. I am not complaining.I am asking for suggestion,already reading some books to solve the issues Pragmatic Programmer; Design portion from B.Stroustrup; Programming and principles by B.Stroustrup;

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• Unresolved external symbol error in c++

  - by Crystal

  I am trying to do a simple hw problem involving namespace, static data members and functions. I am getting an unresolved external symbol error Error 1 error LNK2001: unresolved external symbol "private: static double JWong::SavingsAccount::annualInterestRate" (?annualInterestRate@SavingsAccount@JWong@@0NA) SavingsAccount.obj SavingsAccount And I don't see why I am getting this error. Maybe I don't know something about static variables compared to regular data members that is causing this error. Here is my code: SavingsAccount.h file #ifndef JWONG_SAVINGSACCOUNT_H #define JWONG_SAVINGSACCOUNT_H namespace JWong { class SavingsAccount { public: // default constructor SavingsAccount(); // constructor SavingsAccount(double savingsBalance); double getSavingsBalance(); void setSavingsBalance(double savingsBalance); double calculateMonthlyInterest(); // static functions static void modifyInterestRate(double newInterestRate); static double getAnnualInterestRest(); private: double savingsBalance; // static members static double annualInterestRate; }; } #endif SavingsAccount.cpp file #include <iostream> #include "SavingsAccount.h" // default constructor, set savingsBalance to 0 JWong::SavingsAccount::SavingsAccount() : savingsBalance(0) {} // constructor JWong::SavingsAccount::SavingsAccount(double savingsBalance) : savingsBalance(savingsBalance) {} double JWong::SavingsAccount::getSavingsBalance() { return savingsBalance; } void JWong::SavingsAccount::setSavingsBalance(double savingsBalance) { this->savingsBalance = savingsBalance; } // returns monthly interest and sets savingsBalance to new amount double JWong::SavingsAccount::calculateMonthlyInterest() { double monthlyInterest = savingsBalance * SavingsAccount::annualInterestRate / 12; setSavingsBalance(savingsBalance + monthlyInterest); return monthlyInterest; } void JWong::SavingsAccount::modifyInterestRate(double newInterestRate) { SavingsAccount::annualInterestRate = newInterestRate; } double JWong::SavingsAccount::getAnnualInterestRest() { return SavingsAccount::annualInterestRate; }

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• How do I add code automatically to a derived function in C++

  - by Ian

  I have code that's meant to manage operations on both a networked client and a server, since there is significant overlap between the two. However, there are a few functions here and there that are meant to be exclusively called by the client or server, and accidentally calling a client function on the server (or vice versa) is a significant source of bugs. To reduce these sorts of programming errors, I'm trying to tag functions so that they'll raise a ruckus if they're misused. My current solution is a simple macro at the start of each function that calls an assert if the client or server accesses members they shouldn't. However, this runs into problems when there are multiple derived instances of classes, in that I have to tag the implementation as client or server side in EVERY child class. What I'd like to be able to do is put a tag in the virtual member's signature in the base class, so that I only have to tag it once and not run into errors by forgetting to do it repeatedly. I've considered putting a check in a base class implementation and then referring to it with something like base::functionName, but that runs into the same issue as far as needing to manually add the function call to every implementation. Ideally, I'd be able to have parent versions of the function called automatically like default constructors do. Does anybody know how to achieve something like this in C++? Is there an alternate approach I should be considering? Thanks!

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• Seeking suggestions on redesigning the interface

  - by ratkok

  As a part of maintaining large piece of legacy code, we need to change part of the design mainly to make it more testable (unit testing). One of the issues we need to resolve is the existing interface between components. The interface between two components is a class that contains static methods only. Simplified example: class ABInterface { static methodA(); static methodB(); ... static methodZ(); }; The interface is used by component A so that different methods can use ABInterface::methodA() in order to prepare some input data and then invoke appropriate functions within component B. Now we are trying to redesign this interface for various reasons: Extending our unit test coverage - we need to resolve this dependency between the components and stubs/mocks are to be introduced The interface between these components diverged from the original design (ie. a lots of newer functions, used for the inter-component i/f are created outside this interface class). The code is old, changed a lot over the time and needs to be refactored. The change should not be disruptive for the rest of the system. We try to limit leaving many test-required artifacts in the production code. Performance is very important and should be no (or very minimal) degradation after the redesign. Code is OO in C++. I am looking for some ideas what approach to take. Any suggestions on how to do this efficiently?

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• Is there a way to force ContourPlot re-check all the points on the each stage of it's recursion algorithm?

  - by Alexey Popkov

  Hello, Thanks to this excellent analysis of the Plot algorithm by Yaroslav Bulatov, I now understand the reason why Plot3D and ContourPlot fail to draw smoothly functions with breaks and discontinuities. For example, in the following case ContourPlot fails to draw contour x^2 + y^2 = 1 at all: ContourPlot[Abs[x^2 + y^2 - 1], {x, -1, 1}, {y, -1, 1}, Contours -> {0}] It is because the algorithm does not go deeply into the region near x^2 + y^2 = 1. It "drops" this region on an initial stage and do not tries to investigate it further. Increasing MaxRecursion does nothing in this sense. And even undocumented option Method -> {Refinement -> {ControlValue -> .01 \[Degree]}} does not help (but makes Plot3D a little bit smoother). The above function is just a simple example. In real life I'm working with very complicated implicit functions that cannot be solved analytically. Is there a way to get ContourPlot to go deeply into such regions near breaks and discontinuities?

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• Wordpress OptimizePress (Theme) error when creating new page

  - by user594777

  I just installed WordPress newest version, also installed OptimizePress Theme. I am getting the following error when trying to add a new page in Word Press. Any help would be appreciated. Warning: mkdir() [function.mkdir]: Permission denied in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clscustomfields.php on line 1578 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clscustomfields.php on line 1581 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clscustomfields.php on line 1584 Warning: mkdir() [function.mkdir]: Permission denied in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clsblogfields.php on line 174 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clsblogfields.php on line 177 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clsblogfields.php on line 180 Warning: mkdir() [function.mkdir]: Permission denied in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clslpcustomfields.php on line 1725 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clslpcustomfields.php on line 1728 Warning: mkdir() [function.mkdir]: No such file or directory in /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clslpcustomfields.php on line 1731 Warning: Cannot modify header information - headers already sent by (output started at /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clscustomfields.php:1578) in /home/admin/domains/mywebsite.com/public_html/wp-includes/functions.php on line 830 Warning: Cannot modify header information - headers already sent by (output started at /home/admin/domains/mywebsite.com/public_html/wp-content/themes/OptimizePress/admin/clscustomfields.php:1578) in /home/admin/domains/mywebsite.com/public_html/wp-includes/functions.php on line 831

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• Modify existing struct alignment in Visual C++

  - by Crend King

  Is there a way to modify the member alignment of an existing struct in Visual C++? Here is the background: I use an 3rd-party library, which uses several structs. To fill up the structs, I pass the address of the struct instance to some functions. Unfortunately, the functions only returns unaligned buffer, so that data of some members are always wrong. /Zp is out of choice, since it breaks the other parts of the program. I know #pragma pack modifies the alignment of the following struct, but I do not want to copy the structs into my code, for the definitions in the library might change in the future. Sample code: test.h: struct am_aligned { BYTE data1[10]; ULONG data2; }; test.cpp: include "test.h" // typedef alignment(1) struct am_aligned am_unaligned int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { char buffer[20] = {}; for (int i = 0; i < sizeof(unaligned_struct); i++) { buffer[i] = i; } am_aligned instance = *(am_aligned*) buffer; return 0; } instance.data2 is 0x0f0e0d0c, while 0x0d0c0b0a is desired. The commented line does not work of course. Thanks for help!

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• Using sigprocmask to implement locks

  - by EpsilonVector

  I'm implementing user threads in Linux kernel 2.4, and I'm using ualarm to invoke context switches between the threads. We have a requirement that our thread library's functions should be uninterruptable, so I looked into blocking signals and learned that using sigprocmask is the standard way to do this. However, it looks like I need to do quite a lot to implement this: sigset_t new_set, old_set; sigemptyset(&new_set); sigaddset(&new_set, SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); This blocks SIGALARM but it does this with 3 function invocations! A lot can happen in the time it takes for these functions to run, including the signal being sent. The best idea I had to mitigate this was temporarily disabling ualarm, like this: sigset_t new_set, old_set; time=ualarm(0,0); sigemptyset(&new_set); sigaddset(&new_set, SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); ualarm(time, 0); Which is fine except that this feels verbose. Isn't there a better way to do this?

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• Apples, oranges, and pointers to the most derived c++ class

  - by Matthew Lowe

  Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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• How to write an intersects for Shapes in android

  - by Rafael T

  I have an written an Object called Shape which has a Point representing the topLeftCorner and a Dimension with represents its width and height. To get the topRightCorner I can simply add the width to the topLeftPoint.x. I use to rotate them on a certain degree around their center. The problem after the rotation is, that my intersects(Shape) method fails, because it does not honor the rotation of the Shapes. The rotation will be the same for each Shape. My current implementation looks like this inside my Shape Object: public boolean intersects(Shape s){ // functions returning a Point of shape s return intersects(s.topLeft()) || intersects(s.topRight()) || intersects(s.bottomLeft()) || intersects(s.bottomRight()) || intersects(s.leftCenter()) || intersects(s.rightCenter()) || intersects(s.center()); } public boolean intersects(Point p){ return p.x >= leftX() && p.x <= rightX() && p.y >= topY() && p.y <= bottomY(); } Basically I need functions like rotatedLeftX() or rotatedTopRight() to work properly. Also for that calculation I think it doesn't matter when the topLeft point before a rotation of ie 90 will turn into topRight... I already read this and this Question here, but do not understand it fully.

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• How can I send GET data to multiple URLs at the same time using cURL?

  - by Rob

  My apologies, I've actually asked this question multiple times, but never quite understood the answers. Here is my current code: while($resultSet = mysql_fetch_array($SQL)){ $ch = curl_init($resultSet['url'] . $fullcurl); //load the urls and send GET data curl_setopt($ch, CURLOPT_TIMEOUT, 2); //Only load it for two seconds (Long enough to send the data) curl_exec($ch); //Execute the cURL curl_close($ch); //Close it off } //end while loop What I'm doing here, is taking URLs from a MySQL Database ($resultSet['url']), appending some extra variables to it, just some GET data ($fullcurl), and simply requesting the pages. This starts the script running on those pages, and that's all that this script needs to do, is start those scripts. It doesn't need to return any output. Just the load the page long enough for the script to start. However, currently it's loading each URL (currently 11) one at a time. I need to load all of them simultaneously. I understand I need to use curl_multi_*, but I haven't the slightest idea on how cURL functions work, so I don't know how to change my code to use curl_multi_* in a while loop. So my questions are: How can I change this code to load all of the URLs simultaneously? Please explain it and not just give me code. I want to know what each individual function does exactly. Will curl_multi_exec even work in a while loop, since the while loop is just sending each row one at a time? And of course, any references, guides, tutorials about cURL functions would be nice, as well. Preferably not so much from php.net, as while it does a good job of giving me the syntax, its just a little dry and not so good with the explanations.

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• Convert C function to Objective C or alternative way to include C library?

  - by Moshe

  Background: I'm new to Objective-C and I've never touched C before. I'm trying to include a C library in my iPhone/iPod Touch project and I could not successfully compile the library's source code using the included instructions, so I've resorted to including the .h and .c files in Xcode. The library is for Hebrew Dates and corresponding Jewish Holidays. It can be found here: http://sourceforge.net/projects/libhdate/ I cannot seem to import the .c files into my implementation files. I can import the .h files though. When I try to use #import "file.c", where file.c is a file that is in XCode, it doesn't work. Why not? I've considered just writing the functions over in Objective-C, albeit only my needed functions and not the whole library. How can I make the following C function work in Objective-C? Are there other things that need to be included/re-coded/compiled? How so? I am almost certain something is missing, but I'm not sure what. Code: int hdate_get_omer_day(hdate_struct const * h) { int omer_day; hdate_struct sixteen_nissan; hdate_set_hdate(&sixteen_nissan, 16, 7, h->hd_year); omer_day = h->hd_jd - sixteen_nissan.hd_jd + 1; if ((omer_day > 49) || (omer_day < 0)) omer_day = 0; return omer_day; } So... should I be converting it, or trying somehow to compile to an appropriate format and how so? (I don't know what format a static library should be in, by the way, or if it should be static... - I'm so lost here....) I appreciate the help!

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• Any utility to test expand C/C++ #define macros?

  - by Randy

  It seems I often spend way too much time trying to get a #define macro to do exactly what i want. I'll post my current delemia below and any help is appreciated. But really the bigger question is whether there is any utility someone could reccomend, to quickly display what a macro is actually doing? It seems like even the slow trial and error process would go much faster if I could see what is wrong. Currently, I'm dynamically loading a long list of functions from a DLL I made. The way I've set things up, the function pointers have the same nanes as the exported functions, and the typedef(s) used to prototyp them have the same names, but with a prepended underscor. So I want to use a define to simplfy assignments of a long long list of function pointers. For example, In the code statement below, 'hexdump' is the name of a typdef'd function point, and is also the name of the function, while _hexdump is the name of the typedef. If GetProcAddress() fails, a failure counter in incremented. if (!(hexdump = (_hexdump)GetProcAddress(h, "hexdump"))) --iFail; So lets say I'd like to rplace each line like the above with a macro, like this... GETADDR_FOR(hexdump ) Well this is the best I've come up with so far. It doesn't work (my // comment is just to prevent text formatting in the message)... // #define GETADDR_FOR(a) if (!(a = (#_#a)GetProcAddress(h, "/""#a"/""))) --iFail; And again, while I'd APPRECIATE an insight into what silly mistake I've made, it would make my day to have a utility that would show me the error of my ways, by simply plugging in my macro

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• What is the rationale to not allow overloading of C++ conversions operator with non-member function

  - by Vicente Botet Escriba

  C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From > operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration> operator boost::posix_time::ptime( const boost::chrono::time_point<Clock, Duration>& from) { using namespace boost; typedef chrono::time_point<Clock, Duration> time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast<duration_t>( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast<long>(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. For a more complete description of the problem, see here or on my Boost.Conversion library.. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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• Low Level Console Input

  - by Soulseekah

  I'm trying to send commands to to the input of a cmd.exe application using the low level read/write console functions. I have no trouble reading the text (scraping) using the ReadConsole...() and WriteConsole() functions after having attached to the process console, but I've not figured out how to write for example "dir" and have the console interpret it as a sent command. Here's a bit of my code: CreateProcess(NULL, "cmd.exe", NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi); AttachConsole(pi.dwProcessId); strcpy(buffer, "dir"); WriteConsole(GetStdHandle(STD_INPUT_HANDLE), buffer, strlen(buffer), &charRead, NULL); STARTUPINFO attributes of the process are all set to zero, except, of course, the .cb attribute. Nothing changes on the screen, however I'm getting an Error 6: Invalid Handle returned from WriteConsole to STD_INPUT_HANDLE. If I write to (STD_OUTPUT_HANDLE) I do get my dir written on the screen, but nothing of course happens. I'm guessing SetConsoleMode() might be of help, but I've tried many mode combinations, nothing helped. I've also created a quick console application that waits for input (scanf()) and echoes back whatever goes in, didn't work. I've also tried typing into the scanf() promp and then peek into the input buffer using PeekConsoleInput(), returns 0, but the INPUT_RECORD array is empty. I'm aware that there is another way around this using WriteConsoleInput() to directly inject INPUT_RECORD structured events into the console, but this would be way too long, I'll have to send each keypress into it. I hope the question is clear. Please let me know if you need any further information. Thanks for your help.

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• Finding What You Need in R: function arguments/parameters from outside the function's package

  - by doug

  Often in R, there are a dozen functions scattered across as many packages--all of which have the same purpose but of course differ in accuracy, performance, theoretical rigor, and so on. How do you gather all of these in one place before you start your task? So for instance: the generic plot function. Setting secondary ticks is much easier (IMHO) using a function outside of the base package, minor.tick(nx=n, ny=n, tick.ratio=n), found in Hmisc. Of course, that doesn't show up in plot's docstring. Likewise, the data-input arguments to 'plot' can be supplied by an object returned from the function 'hexbin', again, from a library outside of the base installation (where 'plot' resides). What would be great obviously is a programmatic way to gather these function arguments from the various libraries and put them in a single namespace. edit: (trying to re-state my example just above more clearly:) the arguments to plot supplied in the base package for, e.g., setting the axis tick frequency are xaxp/yaxp; however, one can also set a/t/f via a function outside of the base package, again, as in the minor.tick function from the Hmisc package--but you wouldn't know that just from looking at the plot method signature. Is there a meta function in R for this? So far, as i come across them, i've been manually gathering them in a TextMate 'snippet' (along with the attendant library imports). This isn't that difficult or time consuming, but i can only update my snippet as i find out about these additional arguments/parameters. Is there a canonical R way to do this, or at least an easier way? Just in case that wasn't clear, i am not talking about the case where multiple packages provide functions directed to the same statistic or view (e.g., 'boxplot' in the base package; 'boxplot.matrix' in gplots; and 'bplots' in Rlab). What i am talking is the case in which the function name is the same across two or more packages.

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• Different programming languages possibilities

  - by b-gen-jack-o-neill

  Hello. This should be very simple question. There are many programming languages out there, compiled into machine code or managed code. I first started with ASM back in high school. Assembler is very nice, since you know what exactly CPU does. Next, (as you can see from my other questions here) I decided to learn C and C++. I choosed C becouse from what I read it is the language with output most close to assembler-written programs. But, what I want to know is, can any other Windows programming language out there call win32 API? To be exact, like C has its special header and functions for win32 api interactions, is this assumed to be some important part of programming language? Or are there any languages that have no support for calling win32 API, or just use console to IO and some functions for basic file IO? Becouse, for Windows programming with graphic output, it is essential to have acess to win32 API. I know this question might seem silly, but still please, help me, I ask for study porposes. Thanks.

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• Best way to implement plugin framework - are DLLs the only way (C/C++ project)?

  - by Microkernel

  Introduction: I am currently developing a document classifier software in C/C++ and I will be using Naive-Bayesian model for classification. But I wanted the users to use any algorithm that they want(or I want in the future), hence I went to separate the algorithm part in the architecture as a plugin that will be attached to the main app @ app start-up. Hence any user can write his own algorithm as a plugin and use it with my app. Problem Statement: The way I am intending to develop this is to have each of the algorithms that user wants to use to be made into a DLL file and put into a specific directory. And at the start, my app will search for all the DLLs in that directory and load them. My Questions: (1) What if a malicious code is made as a DLL (and that will have same functions mandated by plugin framework) and put into my plugins directory? In that case, my app will think that its a plugin and picks it and calls its functions, so the malicious code can easily bring down my entire app down (In the worst case could make my app as a malicious code launcher!!!). (2) Is using DLLs the only way available to implement plugin design pattern? (Not only for the fear of malicious plugin, but its a generic question out of curiosity :) ) (3) I think a lot of softwares are written with plugin model for extendability, if so, how do they defend against such attacks? (4) In general what do you think about my decision to use plugin model for extendability (do you think I should look at any other alternatives?) Thank you -MicroKernel :)

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• Omit return type in C++0x

  - by Clinton

  I've recently found myself using the following macro with gcc 4.5 in C++0x mode: #define RETURN(x) -> decltype(x) { return x; } And writing functions like this: template <class T> auto f(T&& x) RETURN (( g(h(std::forward<T>(x))) )) I've been doing this to avoid the inconvenience having to effectively write the function body twice, and having keep changes in the body and the return type in sync (which in my opinion is a disaster waiting to happen). The problem is that this technique only works on one line functions. So when I have something like this (convoluted example): template <class T> auto f(T&& x) -> ... { auto y1 = f(x); auto y2 = h(y1, g1(x)); auto y3 = h(y1, g2(x)); if (y1) { ++y3; } return h2(y2, y3); } Then I have to put something horrible in the return type. Furthermore, whenever I update the function, I'll need to change the return type, and if I don't change it correctly, I'll get a compile error if I'm lucky, or a runtime bug in the worse case. Having to copy and paste changes to two locations and keep them in sync I feel is not good practice. And I can't think of a situation where I'd want an implicit cast on return instead of an explicit cast. Surely there is a way to ask the compiler to deduce this information. What is the point of the compiler keeping it a secret? I thought C++0x was designed so such duplication would not be required.

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• Fastest way to clamp a real (fixed/floating point) value?

  - by Niklas

  Hi, Is there a more efficient way to clamp real numbers than using if statements or ternary operators? I want to do this both for doubles and for a 32-bit fixpoint implementation (16.16). I'm not asking for code that can handle both cases; they will be handled in separate functions. Obviously, I can do something like: double clampedA; double a = calculate(); clampedA = a > MY_MAX ? MY_MAX : a; clampedA = a < MY_MIN ? MY_MIN : a; or double a = calculate(); double clampedA = a; if(clampedA > MY_MAX) clampedA = MY_MAX; else if(clampedA < MY_MIN) clampedA = MY_MIN; The fixpoint version would use functions/macros for comparisons. This is done in a performance-critical part of the code, so I'm looking for an as efficient way to do it as possible (which I suspect would involve bit-manipulation) EDIT: It has to be standard/portable C, platform-specific functionality is not of any interest here. Also, MY_MIN and MY_MAX are the same type as the value I want clamped (doubles in the examples above).

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• What is the difference between these two linq implementations?

  - by Mahesh Velaga

  I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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• Creating PHP strings using other variables...works manually, can't figure out how automatically

  - by Matt

  Hello, I'm trying to get a variable to be formed automatically using data pulled from a mysql database. I know the data is being pulled from the database in some form resembling its original form, but that data does not act the same as data that is manually typed and assigned to a string. For example, if a cell in a mysql table says... I said "goodbye" before I left. She also said "goodbye." ...and I manually copy/paste it and add the necessary escapes... $string1 = " I said \"goodbye\" before I left. She also said \"goodbye.\" "; ...that does not equal... $string1 = $mysqlResultArray['specificCellWithQuoteShownAbove'] Interestingly, if I echo both versions of $string1 and view the output, they appear to be exactly the same. But they do not function the same when put through various functions I've created. The functions only work if I do the manual copy/paste method--which is not what I want, obviously. I'm not sure if it has to do with the line breaks or the escapes--or some combination of the two. But while both strings are superficially the same, they are apparently functionally different and I don't know why. So how can I create $string1 without manually copy/pasting the contents from the mysql entry and instead querying for the data and assigning it to $string1 in such a way that it's exactly functionally equivalent as the manual copy/pasted string?

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• C++ linker unresolved external symbol (again;) from other source file *.obj file. (VC++ express)

  - by bua

  Hi there, I'm back to C/C++ after some break. I've a following problem: I've a solution where I've several projects (compilable and linkable). Now I need to add another project to this solution which depends on some sources from other projects. My new project compiles without any problems (I've added "existing sources" to my project). the error: 1>Linking... 1>LicenceManager.obj : error LNK2019: unresolved external symbol "int __cdecl saveLic(char *,struct Auth *)" (?saveLic@@YAHPADPAUAuth@@@Z) referenced in function "public: void __thiscall LicenceManager::generateLicence(int,char *)" (?generateLicence@LicenceManager@@QAEXHPAD@Z) 1>LicenceManager.obj : error LNK2019: unresolved external symbol "void __cdecl getSysInfo(struct Auth *)" (?getSysInfo@@YAXPAUAuth@@@Z) referenced in function "public: void __thiscall LicenceManager::generateLicence(int,char *)" (?generateLicence@LicenceManager@@QAEXHPAD@Z) Functions saveLic, and getSysInfo are defined in files which I've added to my new project from existing ones. There is object file created during compilation with those functions in target dir, but my LicenceManager class doesn't want to link. I use some extern "C" , and #pragma pack somewhere, but no more fancy stuff. I think every directory, lib and other necessary dependencies are visible in settings for this project. Thanks for any advice.

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• Organising UI code in .NET forms

  - by sb3700

  Hi I'm someone who has taught myself programming, and haven't had any formal training in .NET programming. A while back, I started C# in order to develop a GUI program to control sensors, and the project has blossomed. I was just wondering how best to organise the code, particularly UI code, in my forms. My forms currently are a mess, or at least seem a mess to me. I have a constructor which initialises all the parameters and creates events. I have a giant State property, which updates the Enabled state of all my form control as users progress through the application (ie: disconnected, connected, setup, scanning) controlled by a States enum. I have 3-10 private variables accessed through properties, some of which have side-effects in changing the values of form elements. I have a lot of "UpdateXXX" functions to handle UI elements that depend on other UI elements - ie: if a sensor is changed, then change the baud rate drop down list. They are separated into regions I have a lot of events calling these Update functions I have a background worker which does all the scanning and analysis. My problem is this seems like a mess, particularly the State property, and is getting unmaintainable. Also, my application logic code and UI code are in the same file and to some degree, intermingled which seems wrong and means I need to do a lot of scrolling to find what I need. How do you structure your .net forms? Thanks

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• memcmp,strcmp,strncmp in C

  - by el10780

  I wrote this small piece of code in C to test memcmp() strncmp() strcmp() functions in C. Here is the code that I wrote: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char** argv) { char *word1="apple",*word2="atoms"; if (strncmp(word1,word2,5)==0) printf("strncmp result.\n"); if (memcmp(word1,word2,5)==0) printf("memcmp result.\n"); if (strcmp(word1,word2)==0) printf("strcmp result.\n"); } Can somebody explain me the differences because I am confused with these three functions?My main problem is that I have a file in which I tokenize its line of it,the problem is that when I tokenize the word "atoms" in the file I have to stop the process of tokenizing.I first tried strcmp() but unfortunately when it reached to the point where the word "atoms" were placed in the file it didn't stop and it continued,but when I used either the memcmp() or the strncmp() it stopped and I was happy.But then I thought,what if there will be a case in which there is one string in which the first 5 letters are a,t,o,m,s and these are being followed by other letters.Unfortunately,my thoughts were right as I tested it using the above code by initializing word1 to "atomsaaaaa" and word2 to atoms and memcmp() and strncmp() in the if statements returned 0.On the other hand strcmp() it didn't.It seems that I must use strcmp(). I have done google searches but I got more confused as I have seen sites and other forums to define these three differently.If it is possible for someone to give me correct explanations/definitions so I can use them correctly in my source code,I would be really grateful.

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