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• Converting C source to C++

  - by Barry Kelly

  How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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• Supporting multiple instances of a plugin DLL with global data

  - by Bruno De Fraine

  Context: I converted a legacy standalone engine into a plugin component for a composition tool. Technically, this means that I compiled the engine code base to a C DLL which I invoke from a .NET wrapper using P/Invoke; the wrapper implements an interface defined by the composition tool. This works quite well, but now I receive the request to load multiple instances of the engine, for different projects. Since the engine keeps the project data in a set of global variables, and since the DLL with the engine code base is loaded only once, loading multiple projects means that the project data is overwritten. I can see a number of solutions, but they all have some disadvantages: You can create multiple DLLs with the same code, which are seen as different DLLs by Windows, so their code is not shared. Probably this already works if you have multiple copies of the engine DLL with different names. However, the engine is invoked from the wrapper using DllImport attributes and I think the name of the engine DLL needs to be known when compiling the wrapper. Obviously, if I have to compile different versions of the wrapper for each project, this is quite cumbersome. The engine could run as a separate process. This means that the wrapper would launch a separate process for the engine when it loads a project, and it would use some form of IPC to communicate with this process. While this is a relatively clean solution, it requires some effort to get working, I don't now which IPC technology would be best to set-up this kind of construction. There may also be a significant overhead of the communication: the engine needs to frequently exchange arrays of floating-point numbers. The engine could be adapted to support multiple projects. This means that the global variables should be put into a project structure, and every reference to the globals should be converted to a corresponding reference that is relative to a particular project. There are about 20-30 global variables, but as you can imagine, these global variables are referenced from all over the code base, so this conversion would need to be done in some automatic manner. A related problem is that you should be able to reference the "current" project structure in all places, but passing this along as an extra argument in each and every function signature is also cumbersome. Does there exist a technique (in C) to consider the current call stack and find the nearest enclosing instance of a relevant data value there? Can the stackoverflow community give some advice on these (or other) solutions?

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• OpenCv Error ( unhandeld exeption) after execute

  - by hamza

  Hi , i m using VS2010 i m trting to make a gray image more bright , the code did compile normaly but no change in the seconde picture , and an error message ( undhadled exeception .. .. ) showed up after that the execute is done showed up here is a peace of my code : int main(int argc, _TCHAR* argv[]) { IplImage *img = cvLoadImage("mra.jpg"); if (!img) { printf("Error: Couldn't open the image file.\n"); return 1; } //IplImage* new_image = getlargersize(img); double Min , Max ; Min = Max = 0 ; Max_Min (img , &Min , &Max); cout<<"the max value in the picture is :"<<Min<<" and the minimum value is :"<<Max<<endl ; IplImage* img2 = eclaircir(Min ,Max ,img); cvNamedWindow("Image:", CV_WINDOW_AUTOSIZE); cvNamedWindow("Image2:", CV_WINDOW_AUTOSIZE); cvShowImage("Image2:", img2); cvShowImage("Image:", img); cvWaitKey(0); cvDestroyWindow("Image2:"); cvDestroyWindow("Image:"); cvReleaseImage(&img2); cvReleaseImage(&img); return 0; } void Max_Min(IplImage* temp , double *min , double *max ){ CvScalar pix ; for (int i = 0 ; i < temp->height ; i++){ for (int j = 0 ; j < temp->width ; j++){ pix = cvGet2D(temp , i , j); if ( pix.val[0] >= *max ){ *max = pix.val[0]; } if ( pix.val[0] <= *min){ *min = pix.val[0]; } } } } IplImage* eclaircir (double min , double max , IplImage* image){ double temp = max - min ; CvScalar pix ; for (int i = 0 ; i < image->height ; i++){ for (int j = 0 ; j < image->width ; j++){ pix = cvGet2D(image , i , j); pix.val[0] = ( pix.val[0] - min)*255 ; pix.val[0] = pix.val[0]/temp ; cvSet2D(image , i , j , pix ); } } return image ; } thanks

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• Endianness conversion and g++ warnings

  - by SuperBloup

  I've got the following C++ code : template <int isBigEndian, typename val> struct EndiannessConv { inline static val fromLittleEndianToHost( val v ) { union { val outVal __attribute__ ((used)); uint8_t bytes[ sizeof( val ) ] __attribute__ ((used)); } ; outVal = v; std::reverse( &bytes[0], &bytes[ sizeof(val) ] ); return outVal; } inline static void convertArray( val v[], uint32_t size ) { // TODO : find a way to map the array for (uint32_t i = 0; i < size; i++) for (uint32_t i = 0; i < size; i++) v[i] = fromLittleEndianToHost( v[i] ); } }; Which work and has been tested (without the used attributes). When compiling I obtain the following errors from g++ (version 4.4.1) || g++ -Wall -Wextra -O3 -o t t.cc || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val)': t.cc|98| warning: 'used' attribute ignored t.cc|99| warning: 'used' attribute ignored || t.cc: In static member function 'static val EndiannessConv<isBigEndian, val>::fromLittleEndianToHost(val) [with int isBigEndian = 1, val = double]': t.cc|148| instantiated from here t.cc|100| warning: unused variable 'outVal' t.cc|100| warning: unused variable 'bytes' I've tried to use the following code : template <int size, typename valType> struct EndianInverser { /* should not compile */ }; template <typename valType> struct EndianInverser<4, valType> { static inline valType reverseEndianness( const valType &val ) { uint32_t castedVal = *reinterpret_cast<const uint32_t*>( &val ); castedVal = (castedVal & 0x000000FF << (3 * 8)) | (castedVal & 0x0000FF00 << (1 * 8)) | (castedVal & 0x00FF0000 >> (1 * 8)) | (castedVal & 0xFF000000 >> (3 * 8)); return *reinterpret_cast<valType*>( &castedVal ); } }; but it break when enabling optimizations due to the type punning. So, why does my used attribute got ignored? Is there a workaround to convert endianness (I rely on the enum to avoid type punning) in templates?

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• functional, bind1st and mem_fun

  - by Neil G

  Why won't this compile? #include <functional> #include <boost/function.hpp> class A { A() { typedef boost::function<void ()> FunctionCall; FunctionCall f = std::bind1st(std::mem_fun(&A::process), this); } void process() {} }; Errors: In file included from /opt/local/include/gcc44/c++/bits/stl_function.h:712, from /opt/local/include/gcc44/c++/functional:50, from a.cc:1: /opt/local/include/gcc44/c++/backward/binders.h: In instantiation of 'std::binder1st<std::mem_fun_t<void, A> >': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:100: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:103: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:106: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:111: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:117: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h: In function 'std::binder1st<_Operation> std::bind1st(const _Operation&, const _Tp&) [with _Operation = std::mem_fun_t<void, A>, _Tp = A*]': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:126: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' In file included from /opt/local/include/boost/function/detail/maybe_include.hpp:13, from /opt/local/include/boost/function/detail/function_iterate.hpp:14, from /opt/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:47, from /opt/local/include/boost/function.hpp:64, from a.cc:2: /opt/local/include/boost/function/function_template.hpp: In static member function 'static void boost::detail::function::void_function_obj_invoker0<FunctionObj, R>::invoke(boost::detail::function::function_buffer&) [with FunctionObj = std::binder1st<std::mem_fun_t<void, A> >, R = void]': /opt/local/include/boost/function/function_template.hpp:913: instantiated from 'void boost::function0<R>::assign_to(Functor) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:722: instantiated from 'boost::function0<R>::function0(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:1064: instantiated from 'boost::function<R()>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' a.cc:7: instantiated from here /opt/local/include/boost/function/function_template.hpp:153: error: no match for call to '(std::binder1st<std::mem_fun_t<void, A> >) ()'

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• c++ templates: problem with member specialization

  - by ChAoS

  I am attempting to create a template "AutoClass" that create an arbitrary class with an arbitrary set of members, such as: AutoClass<int,int,double,double> a; a.set(1,1); a.set(0,2); a.set(3,99.7); std::cout << "Hello world! " << a.get(0) << " " << a.get(1) << " " << a.get(3) << std::endl; By now I have an AutoClass with a working "set" member: class nothing {}; template < typename T1 = nothing, typename T2 = nothing, typename T3 = nothing, typename T4 = nothing, typename T5 = nothing, typename T6 = nothing> class AutoClass; template <> class AutoClass<nothing, nothing, nothing, nothing, nothing, nothing> { public: template <typename U> void set(int n,U v){} }; template < typename T1, typename T2, typename T3, typename T4, typename T5, typename T6> class AutoClass: AutoClass<T2,T3,T4,T5,T6> { public: T1 V; template <typename U> void set(int n,U v) { if (n <= 0) V = v; else AutoClass<T2,T3,T4,T5,T6>::set(n-1,v); } }; and I started to have problems implementing the corresponding "get". This approach doesn't compile: template < typename T1, typename T2, typename T3, typename T4, typename T5, typename T6> class AutoClass: AutoClass<T2,T3,T4,T5,T6> { public: T1 V; template <typename U> void set(int n,U v) { if (n <= 0) V = v; else AutoClass<T2,T3,T4,T5,T6>::set(n-1,v); } template <typename W> W get(int n) { if (n <= 0) return V; else return AutoClass<T2,T3,T4,T5,T6>::get(n-1); } template <> T1 get(int n) { if (n <= 0) return V; else return AutoClass<T2,T3,T4,T5,T6>::get(n-1); } }; Besides, it seems I need to implement get for the <nothing, nothing, nothing, nothing, nothing, nothing> specialization. Any Idea on how to solve this?

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• help me to choose the best soulotion for my purpose to build my software.

  - by rima

  before answer me plz thinking about the futures of these kind of program and answer me plz. I wanna get some data from oracle server like: 1-get all the function,package,procedure and etc for showing them or drop them & etc... 2-compile my *.sql files,get the result if they have problem & etc... becuz I was beginner in oracle first of all I for solve the second problem I try to connect to sqlPlus by RUN sqlplus and trace the output(I mean,I change the output stream of shell and trace what happend and handle the assigned message to customer. NOW THIS PART SUCCEED. just a little bit I have problem with get all result because the output is asynchronous.any way... [in this case I log in to oracle Server by send argument to the sqlplus by make a process in c#] after that I try to get all function,package or procedure name,but I have problem in speed!so I try to use oracle.DataAccess.dll to connect the database. now I m so confusing about: which way is correct way to build a program that work like Oracle Developer! I do not have any experience for like these program how work. If Your answer is I must use the second way follow this part plz: I search a little bit the Golden,PLedit (Benthic software),I have little bit problem how I must create the connection string?because I thinking about how I can find the host name or port number that oracle work on them?? am I need read the TNSNames.Ora file? IF your answer is I must use the first way follow this part plz: do u have any Idea for how I parse the output?because for example the result of a table is so confusing...[i can handle & program it but I really need someone experience,because the important things to me learn how such software work so nice and with quick response?] All of the has different style in output... If you are not sure Can u help me which book can help me in this way i become expert? becuz for example all the C# write just about how u can connect to DB and the DB books write how u can use this DB program,I looking for a book that give me some Idea how develop an interface for do transaction between these two.not simple send and receive data,for example how write a compiler for them. the language of book is not different for me i know C#,java,VB,sql,Oracle Thanks.

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• Is it correct or incorrect for a Java JAR to contain its own dependencies?

  - by 4herpsand7derpsago

  I guess this is a two-part question. I am trying to write my own Ant task (MyFirstTask) that can be used in other project's build.xml buildfiles. To do this, I need to compile and package my Ant task inside its own JAR. Because this Ant task that I have written is fairly complicated, it has about 20 dependencies (other JAR files), such as using XStream for OX-mapping, Guice for DI, etc. I am currently writing the package task in the build.xml file inside the MyFirstTask project (the buildfile that will package myfirsttask.jar, which is the reusable Ant task). I am suddenly realizing that I don't fully understand the intention of a Java JAR. Is it that a JAR should not contain dependencies, and leave it to the runtime configuration (the app container, the runtime environment, etc.) to supply it with the dependencies it needs? I would assume if this is the case, an executable JAR is an exception to the rule, yes? Or, is it the intention for Java JARs to also include their dependencies? Either way, I don't want to be forcing my users to be copying-n-pasting 25+ JARs into their Ant libs; that's just cruel. I like the way WAR files are set up, where the classpath for dependencies is defined under the classes/ directory. I guess, ultimately, I'd like my JAR structure to look like: myfirsttask.jar/ com/ --> the root package of my compiled binaries config/ --> config files, XML, XSD, etc. classes/ --> all dependencies, guice-3.0.jar, xstream-1.4.3.jar, etc. META-INF/ MANIFEST.MF I assume that in order to accomplish this (and get the runtime classpath to also look into the classes/ directory), I'll need to modify the MANIFEST.MF somehow (I know there's a manifest attribute called ClassPath, I believe?). I'm just having a tough time putting everything together, and have a looming/lingering question about the very intent of JARs to begin with. Can someone please confirm whether Oracle intends for JARs to contain their dependencies or not? And, either way, what I would have to do in the manifest (or anywhere else) to make sure that, at runtime, the classpath can find the dependencies stored under the classes/ directory? Thanks in advance!

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• What are some things you'd like fresh college grads to know?

  - by bradhe

  So I proposed this to the Reddit community and I'd like to get SO's perspective on this. This is pretty much the copypasta of what I put there. I was thinking about this last night and thought it would be neat to compile a list. I'm still a pretty fresh college grad -- been in industry for 2 years -- but I think that I might have a few interesting things to lend. You don't know as much as you think you do. Somehow, college students think they know a lot more than they do (or maybe that was just me). Likewise, they think they can do more than they actually can. You should fairly assess your skills. QA people are not out to get you. Humans introduce bugs to code. It's not (nescessarily) a personal reflection on you and your skills if your code has a bug and it's caught by the QA/testing team. Listen to your senior (developers). They are not actually fuddy duddies who don't know about the new L337 hax in Ruby (okay, sometimes they are, but still...). They have a wealth of knowledge that you can learn from and it's in your best interest to do so. You will most likely not be doing what you want to for a while. This is mostly true in the corporate world -- startups are a different matter. Also, this is due to more than just the economy, man! Junior devs need to earn their keep, so to speak. Everyone wants to be lead dev on the next project and there are a lot of people in line ahead of you! For every elite developer there are 100 average developers. Joel Spolsky, I'm looking at you. Somehow this concept of ninja coders has really ingrained itself in our culture. While I encourage you to be the best you can be don't be disappointed if people aren't writing blog posts about you in the near future. Anyone else have anything they would see added to this list?

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• Having problems creating an array from XML data in Acrobat Javascript, please help if you can

  - by Kevin Minke

  I have a manually created array that already works example below: var PartsData = { 179: { ref:"", partNum: "201-2007-C00-00", descript: "System Monitor Card (Tracewell Only)", cage: "39764", qty: "1", SMR: "XBOZZ", UOC: "A" }}; Now this array above is is just one value in the array and it works fine. Here is the XML that I am trying to use to dynamically change the values. <?xml version="1.0" encoding="utf-8"?> <partsTables> <partsList> <part sheetNum="ta1"> <breakDownIndexNo>-1 </breakDownIndexNo> <referenceDesg/> <indent>20534220P01 </indent> <description/> <cage>TAC RI, GRADE-A SHOCK (TEC RACK), ALT P/N 72304-1</cage> <qtyPerAssy>23991 </qtyPerAssy> <smr>1 </smr> <uoc>ADODD </uoc> <blank/> </part> </partsList> </partsTables> I have this parsing just fine in Acrobat. Now I want to make the array work for me in using these values. if I have the following below it will work. Where part.item(i).indent.value equals the value of the indent node, etc. newArr = { 179: { ref: part.item(i).referenceDesg.value, partNum: part.item(i).indent.value, descript: part.item(i).cage.value, cage: part.item(i).qtyPerAssy.value, qty: part.item(i).smr.value, SMR: part.item(i).uoc.value, UOC: part.item(i).blank.value}}; As soon as I try to make the 179 value, which is in the breakDownIndexNo node, dynamic by using the direct part.item(i).breakDownIndexNo.value it will not compile. Acrobat is using javascript so I'm not sure why I can not get this to parse. I have tried to create a variable out of the breakDownIndexNo node and typed it to both a String and an Integer. this will let it create the array but it will not let me output from the array. newArr[indexNum].partNum gives me "no properties" where newArr[179].partNum if I were to manually set the index number to 179 will print out the value of part.item(i).indent.value. If any of you have an idea or an answer please let me know.

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• Thread sleep and thread join.

  - by Dhruv Gairola

  hi guys, if i put a thread to sleep in a loop, netbeans gives me a caution saying Invoking Thread.sleep in loop can cause performance problems. However, if i were to replace the sleep with join, no such caution is given. Both versions compile and work fine tho. My code is below (check the last few lines for "Thread.sleep() vs t.join()"). public class Test{ //Display a message, preceded by the name of the current thread static void threadMessage(String message) { String threadName = Thread.currentThread().getName(); System.out.format("%s: %s%n", threadName, message); } private static class MessageLoop implements Runnable { public void run() { String importantInfo[] = { "Mares eat oats", "Does eat oats", "Little lambs eat ivy", "A kid will eat ivy too" }; try { for (int i = 0; i < importantInfo.length; i++) { //Pause for 4 seconds Thread.sleep(4000); //Print a message threadMessage(importantInfo[i]); } } catch (InterruptedException e) { threadMessage("I wasn't done!"); } } } public static void main(String args[]) throws InterruptedException { //Delay, in milliseconds before we interrupt MessageLoop //thread (default one hour). long patience = 1000 * 60 * 60; //If command line argument present, gives patience in seconds. if (args.length > 0) { try { patience = Long.parseLong(args[0]) * 1000; } catch (NumberFormatException e) { System.err.println("Argument must be an integer."); System.exit(1); } } threadMessage("Starting MessageLoop thread"); long startTime = System.currentTimeMillis(); Thread t = new Thread(new MessageLoop()); t.start(); threadMessage("Waiting for MessageLoop thread to finish"); //loop until MessageLoop thread exits while (t.isAlive()) { threadMessage("Still waiting..."); //Wait maximum of 1 second for MessageLoop thread to //finish. /*******LOOK HERE**********************/ Thread.sleep(1000);//issues caution unlike t.join(1000) /**************************************/ if (((System.currentTimeMillis() - startTime) > patience) && t.isAlive()) { threadMessage("Tired of waiting!"); t.interrupt(); //Shouldn't be long now -- wait indefinitely t.join(); } } threadMessage("Finally!"); } } As i understand it, join waits for the other thread to complete, but in this case, arent both sleep and join doing the same thing? Then why does netbeans throw the caution?

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• C++ DLL creation for C# project - No functions exported

  - by Yeti

  I am working on a project that requires some image processing. The front end of the program is C# (cause the guys thought it is a lot simpler to make the UI in it). However, as the image processing part needs a lot of CPU juice I am making this part in C++. The idea is to link it to the C# project and just call a function from a DLL to make the image processing part and allow to the C# environment to process the data afterwards. Now the only problem is that it seems I am not able to make the DLL. Simply put the compiler refuses to put any function into the DLL that I compile. Because the project requires some development time testing I have created two projects into a C++ solution. One is for the Dll and another console application. The console project holds all the files and I just include the corresponding header into my DLL project file. I thought the compiler should take out the functions that I marked as to be exported and make the DLL from them. Nevertheless this does not happens. Here it is how I defined the function in the header: extern "C" __declspec(dllexport) void _stdcall RobotData(BYTE* buf, int** pToNewBackgroundImage, int* pToBackgroundImage, bool InitFlag, ObjectInformation* robot1, ObjectInformation* robot2, ObjectInformation* robot3, ObjectInformation* robot4, ObjectInformation* puck); extern "C" __declspec(dllexport) CvPoint _stdcall RefPointFinder(IplImage* imgInput, CvRect &imgROI, CvScalar &refHSVColorLow, CvScalar &refHSVColorHi ); Followed by the implementation in the cpp file: extern "C" __declspec(dllexport) CvPoint _stdcall RefPointFinder(IplImage* imgInput, CvRect &imgROI,&refHSVColorLow, CvScalar &refHSVColorHi ) { \\... return cvPoint((int)( M10/M00) + imgROI.x, (int)( M01/M00 ) + imgROI.y) ;} extern "C" __declspec(dllexport) void _stdcall RobotData(BYTE* buf, int** pToNewBackgroundImage, int* pToBackgroundImage, bool InitFlag, ObjectInformation* robot1, ObjectInformation* robot2, ObjectInformation* robot3, ObjectInformation* robot4, ObjectInformation* puck) { \\ ...}; And my main file for the DLL project looks like: #ifdef _MANAGED #pragma managed(push, off) #endif /// <summary> Include files. </summary> #include "..\ImageProcessingDebug\ImageProcessingTest.h" #include "..\ImageProcessingDebug\ImageProcessing.h" BOOL APIENTRY DllMain( HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) { return TRUE; } #ifdef _MANAGED #pragma managed(pop) #endif Needless to say it does not work. A quick look with DLL export viewer 1.36 reveals that no function is inside the library. I don't get it. What I am doing wrong ? As side not I am using the C++ objects (and here it is the C++ DLL part) such as the vector. However, only for internal usage. These will not appear in the headers of either function as you can observe from the previous code snippets. Any ideas? Thx, Bernat

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• How to use sound and images in a Java applet?

  - by Click Upvote

  Question 1: How should I structure my project so the sound and images files can be loaded most easily? Right now, I have the folder: C:\java\pacman with the sub-directory C:\java\pacman\src containing all the code, and C:\java\pacman\assets containing the images and .wav files. Is this the best structure or should I put the assets somewhere else? Question 2: What's the best way to refer to the images/sounds without using the full path e.g C:\java\pacman\assets\something.png to them? If I use the getCodeBase() function it seems to refer to the C:\java\pacman\bin instead of C:\java\pacman\. I want to use such a function/class which would work automatically when i compile the applet in a jar as well as right now when I test the applet through eclipse. Question 3: How should I load the images/sounds? This is what I'm using now: 1) For general images: import java.awt.Image; public Image getImg(String file) { //imgDir in this case is a hardcoded string containing //"C:\\java\\pacman\\assets\\" file=imgDir + file; return new ImageIcon(file).getImage(); } The images returned from this function are used in the drawImage method of the Graphics class in the paint method of the applet. 2) For a buffered image, which is used to get subImages and load sprites from a sprite sheet: public BufferedImage getSheet() throws IOException { return ImageIO.read(new File(img.getPath("pacman-sprites.png"))); } Later: public void loadSprites() { BufferedImage sheet; try { sheet=getSheet(); redGhost.setNormalImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setUpImg(sheet.getSubimage(0, 60, 20, 20)); redGhost.setDownImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setLeftImg(sheet.getSubimage(30, 60, 20, 20)); redGhost.setRightImg(sheet.getSubimage(60, 60, 20, 20)); } catch (IOException e) { System.out.println("Couldnt open file!"); System.out.println(e.getLocalizedMessage()); } } 3) For sound files: import sun.audio.*; import java.io.*; public synchronized void play() { try { InputStream in = new FileInputStream(filename); AudioStream as = new AudioStream(in); AudioPlayer.player.start(as); } catch (IOException e) { e.printStackTrace(); } }

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• c++ global operator not playing well with template class

  - by John

  ok, i found some similar posts on stackoverflow, but I couldn't find any that pertained to my exact situation and I was confused with some of the answers given. Ok, so here is my problem: I have a template matrix class as follows: template <typename T, size_t ROWS, size_t COLS> class Matrix { public: template<typename, size_t, size_t> friend class Matrix; Matrix( T init = T() ) : _matrix(ROWS, vector<T>(COLS, init)) { /*for( int i = 0; i < ROWS; i++ ) { _matrix[i] = new vector<T>( COLS, init ); }*/ } Matrix<T, ROWS, COLS> & operator+=( const T & value ) { for( vector<T>::size_type i = 0; i < this->_matrix.size(); i++ ) { for( vector<T>::size_type j = 0; j < this->_matrix[i].size(); j++ ) { this->_matrix[i][j] += value; } } return *this; } private: vector< vector<T> > _matrix; }; and I have the following global function template: template<typename T, size_t ROWS, size_t COLS> Matrix<T, ROWS, COLS> operator+( const Matrix<T, ROWS, COLS> & lhs, const Matrix<T, ROWS, COLS> & rhs ) { Matrix<T, ROWS, COLS> returnValue = lhs; return returnValue += lhs; } To me, this seems to be right. However, when I try to compile the code, I get the following error (thrown from the operator+ function): binary '+=' : no operator found which takes a right-hand operand of type 'const matrix::Matrix<T,ROWS,COLS>' (or there is no acceptable conversion) I can't figure out what to make of this. Any help if greatly appreciated!

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• Linux, GNU GCC, ld, version scripts and the ELF binary format -- How does it work??

  - by themoondothshine

  Hey all, I'm trying to learn more about library versioning in Linux and how to put it all to work. Here's the context: -- I have two versions of a dynamic library which expose the same set of interfaces, say libsome1.so and libsome2.so. -- An application is linked against libsome1.so. -- This application uses libdl.so to dynamically load another module, say libmagic.so. -- Now libmagic.so is linked against libsome2.so. Obviously, without using linker scripts to hide symbols in libmagic.so, at run-time all calls to interfaces in libsome2.so are resolved to libsome1.so. This can be confirmed by checking the value returned by libVersion() against the value of the macro LIB_VERSION. -- So I try next to compile and link libmagic.so with a linker script which hides all symbols except 3 which are defined in libmagic.so and are exported by it. This works... Or at least libVersion() and LIB_VERSION values match (and it reports version 2 not 1). -- However, when some data structures are serialized to disk, I noticed some corruption. In the application's directory if I delete libsome1.so and create a soft link in its place to point to libsome2.so, everything works as expected and the same corruption does not happen. I can't help but think that this may be caused due to some conflict in the run-time linker's resolution of symbols. I've tried many things, like trying to link libsome2.so so that all symbols are alised to symbol@@VER_2 (which I am still confused about because the command nm -CD libsome2.so still lists symbols as symbol and not symbol@@VER_2)... Nothing seems to work!!! Help!!!!!! Edit: I should have mentioned it earlier, but the app in question is Firefox, and libsome1.so is libsqlite3.so shipped with it. I don't quite have the option of recompiling them. Also, using version scripts to hide symbols seems to be the only solution right now. So what really happens when symbols are hidden? Do they become 'local' to the SO? Does rtld have no knowledge of their existence? What happens when an exported function refers to a hidden symbol?

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• creating an array of objects in c++

  - by tim22

  I'm trying to create an array of objects in c++. I'm creating a employee object, from my constructor in my company class here: employee obj(int tempIdNum, double tempBase, double tempSales, double tempRate); emp[tempcount]=obj; (this doesn't work?) Emp is the name of the array which is defined here, located in my company h file. Employee emp[4]; more code: Company::Company(string name, string fileName){ string str; int tempcount; int tempIdnum; double tempBase; double tempSales; double tempRate; double num; double arr[16]; this->name=name; //Commission temp; ifstream readFile; readFile.open("fileName"); int inc=0; while(tempcount<4){ for(int i=0+inc; i<4+inc; i++){ readFile>>num; arr[i-inc]=num; } tempIdnum=(int)(arr[0]); tempBase=arr[1]; tempSales=arr[2]; tempRate=arr[3]; Employee obj(int tempIdNum, double tempBase, double tempSales, double tempRate); emp[tempcount]=obj; inc+=4; tempcount++; } readFile.close(); } Here is some more from my h file #include <string> include "Commission.h" using namespace std; ifndef Company_H define Company_H class Company{ private: string name; //name of company Employee emp[4]; //array of payrool info about 4 commission employees int numEmp; //number of employees public: Company(); Company(string name, string fileName); ~Company(); string getName(); Commission getEmployee(int element); int getNumEmp(); }; endif enter code here Does not compile: 46 E:\exercise2\Company.cpp no match for 'operator=' in '((Company*)this)-Company::emp[tempcount] = obj'

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• C++ SQLDriverConnect API

  - by harshalkreddy

  Hi, I am using visual studio 2008 and sql server 2008 for developing application(SQL server is in my system). I need to fetch some fields from the database. I am using the SQLDriverConnect API to connect to the database. If I use the "SQL_DRIVER_PROMPT" I will get pop window to select the data source. I don't want this window to appear. As per my understanding this window will appear if we provide insufficient information in the connection string. I think I have provided all the information. I am trying to connect with windows authentication. I tried different options but still no luck. Please help me in solving this problem. Below is the code that I am using: //******************************************************************************** // SQLDriverConnect_ref.cpp // compile with: odbc32.lib user32.lib #include <windows.h> #include <sqlext.h> int main() { SQLHENV henv; SQLHDBC hdbc; SQLHSTMT hstmt; SQLRETURN retcode; SQLWCHAR OutConnStr[255]; SQLSMALLINT OutConnStrLen; SQLCHAR ConnStrIn[255] = "DRIVER={SQL Server};SERVER=(local);DSN=MyDSN;DATABASE=MyDatabase;Trusted_Connection=yes;"; //SQLWCHAR *ConntStr =(SQLWCHAR *) "DRIVER={SQL Server};DSN=MyDSN;"; HWND desktopHandle = GetDesktopWindow(); // desktop's window handle // Allocate environment handle retcode = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv); // Set the ODBC version environment attribute if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) { retcode = SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER*)SQL_OV_ODBC3, 0); // Allocate connection handle if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) { retcode = SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc); // Set login timeout to 5 seconds if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) { SQLSetConnectAttr(hdbc, SQL_LOGIN_TIMEOUT, (SQLPOINTER)5, 0); retcode = SQLDriverConnect( // SQL_NULL_HDBC hdbc, desktopHandle, (SQLWCHAR *)ConnStrIn, SQL_NTS, OutConnStr, 255, &OutConnStrLen, SQL_DRIVER_NOPROMPT); // Allocate statement handle if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) { retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt); // Process data if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) { SQLFreeHandle(SQL_HANDLE_STMT, hstmt); } SQLDisconnect(hdbc); } SQLFreeHandle(SQL_HANDLE_DBC, hdbc); } } SQLFreeHandle(SQL_HANDLE_ENV, henv); } } //******************************************************************************** Thanks in advance, Harsha

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• CultureManager issue

  - by Serge

  I have a bug I don't understand. While the following works fine: Resources.Classes.AFieldFormula.DirectFieldFormula this one throws an exception: new ResourceManager(typeof(Resources.Classes.AFieldFormula)).GetString("DirectFieldFormula"); Could not find any resources appropriate for the specified culture or the neutral culture. Make sure \"Resources.Classes.AFieldFormula.resources\" was correctly embedded or linked into assembly \"MygLogWeb\" at compile time, or that all the satellite assemblies required are loadable and fully signed. How comes? Resource designer.cs file: //------------------------------------------------------------------------------ // <auto-generated> // This code was generated by a tool. // Runtime Version:4.0.30319.18408 // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------ namespace Resources.Classes { using System; /// <summary> /// A strongly-typed resource class, for looking up localized strings, etc. /// </summary> // This class was auto-generated by the StronglyTypedResourceBuilder // class via a tool like ResGen or Visual Studio. // To add or remove a member, edit your .ResX file then rerun ResGen // with the /str option, or rebuild your VS project. [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "4.0.0.0")] [global::System.Diagnostics.DebuggerNonUserCodeAttribute()] [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()] public class AFieldFormula { private static global::System.Resources.ResourceManager resourceMan; private static global::System.Globalization.CultureInfo resourceCulture; [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")] internal AFieldFormula() { } /// <summary> /// Returns the cached ResourceManager instance used by this class. /// </summary> [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)] public static global::System.Resources.ResourceManager ResourceManager { get { if (object.ReferenceEquals(resourceMan, null)) { global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("MygLogWeb.Classes.AFieldFormula", typeof(AFieldFormula).Assembly); resourceMan = temp; } return resourceMan; } } /// <summary> /// Overrides the current thread's CurrentUICulture property for all /// resource lookups using this strongly typed resource class. /// </summary> [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)] public static global::System.Globalization.CultureInfo Culture { get { return resourceCulture; } set { resourceCulture = value; } } /// <summary> /// Looks up a localized string similar to Direct field. /// </summary> public static string DirectFieldFormula { get { return ResourceManager.GetString("DirectFieldFormula", resourceCulture); } } } }

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• Multi-threaded random_r is slower than single threaded version.

  - by Nixuz

  The following program is essentially the same the one described here. When I run and compile the program using two threads (NTHREADS == 2), I get the following run times: real 0m14.120s user 0m25.570s sys 0m0.050s When it is run with just one thread (NTHREADS == 1), I get run times significantly better even though it is only using one core. real 0m4.705s user 0m4.660s sys 0m0.010s My system is dual core, and I know random_r is thread safe and I am pretty sure it is non-blocking. When the same program is run without random_r and a calculation of cosines and sines is used as a replacement, the dual-threaded version runs in about 1/2 the time as expected. #include <pthread.h> #include <stdlib.h> #include <stdio.h> #define NTHREADS 2 #define PRNG_BUFSZ 8 #define ITERATIONS 1000000000 void* thread_run(void* arg) { int r1, i, totalIterations = ITERATIONS / NTHREADS; for (i = 0; i < totalIterations; i++){ random_r((struct random_data*)arg, &r1); } printf("%i\n", r1); } int main(int argc, char** argv) { struct random_data* rand_states = (struct random_data*)calloc(NTHREADS, sizeof(struct random_data)); char* rand_statebufs = (char*)calloc(NTHREADS, PRNG_BUFSZ); pthread_t* thread_ids; int t = 0; thread_ids = (pthread_t*)calloc(NTHREADS, sizeof(pthread_t)); /* create threads */ for (t = 0; t < NTHREADS; t++) { initstate_r(random(), &rand_statebufs[t], PRNG_BUFSZ, &rand_states[t]); pthread_create(&thread_ids[t], NULL, &thread_run, &rand_states[t]); } for (t = 0; t < NTHREADS; t++) { pthread_join(thread_ids[t], NULL); } free(thread_ids); free(rand_states); free(rand_statebufs); } I am confused why when generating random numbers the two threaded version performs much worse than the single threaded version, considering random_r is meant to be used in multi-threaded applications.

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• Why does the Ternary\Conditional operator seem significantly faster

  - by Jodrell

  Following on from this question, which I have partially answered. I compile this console app in x64 Release Mode, with optimizations on, and run it from the command line without a debugger attached. using System; using System.Diagnostics; class Program { static void Main() { var stopwatch = new Stopwatch(); var ternary = Looper(10, Ternary); var normal = Looper(10, Normal); if (ternary != normal) { throw new Exception(); } stopwatch.Start(); ternary = Looper(10000000, Ternary); stopWatch.Stop(); Console.WriteLine( "Ternary took {0}ms", stopwatch.ElapsedMilliseconds); stopwatch.Start(); normal = Looper(10000000, Normal); stopWatch.Stop(); Console.WriteLine( "Normal took {0}ms", stopwatch.ElapsedMilliseconds); if (ternary != normal) { throw new Exception(); } Console.ReadKey(); } static int Looper(int iterations, Func<bool, int, int> operation) { var result = 0; for (int i = 0; i < iterations; i++) { var condition = result % 11 == 4; var value = ((i * 11) / 3) % 5; result = operation(condition, value); } return result; } static int Ternary(bool condition, in value) { return value + (condition ? 2 : 1); } static int Normal(int iterations) { if (condition) { return = 2 + value; } return = 1 + value; } } I don't get any exceptions and the output to the console is somthing close to, Ternary took 107ms Normal took 230ms When I break down the CIL for the two logical functions I get this, ... Ternary ... { : ldarg.1 // push second arg : ldarg.0 // push first arg : brtrue.s T // if first arg is true jump to T : ldc.i4.1 // push int32(1) : br.s F // jump to F T: ldc.i4.2 // push int32(2) F: add // add either 1 or 2 to second arg : ret // return result } ... Normal ... { : ldarg.0 // push first arg : brfalse.s F // if first arg is false jump to F : ldc.i4.2 // push int32(2) : ldarg.1 // push second arg : add // add second arg to 2 : ret // return result F: ldc.i4.1 // push int32(1) : ldarg.1 // push second arg : add // add second arg to 1 : ret // return result } Whilst the Ternary CIL is a little shorter, it seems to me that the execution path through the CIL for either function takes 3 loads and 1 or 2 jumps and a return. Why does the Ternary function appear to be twice as fast. I underdtand that, in practice, they are both very quick and indeed, quich enough but, I would like to understand the discrepancy.

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• Passing enums to functions in C++

  - by rocknroll

  Hi all, I have a header file with all the enums listed (#ifndef #define #endif construct has been used to avoid multiple inclusion of the file) that I use in multiple cpp files in my application.One of the enums in the files is enum StatusSubsystem {ENABLED,INCORRECT_FRAME,INVALID_DATA,DISABLED}; There are functions in the application delcared as ShowStatus(const StatusSubsystem&); Earlier in the application when I made calls to the above function like ShowStatus(INCORRECT_FRAME); my application used to compile perfectly. But after some code was added The compilation halts giving the following error: File.cpp:71: error: invalid conversion from `int' to `StatusSubsystem' File.cpp:71: error: initializing argument 1 of `void Class::ShowStatus(const StatusSubsystem&) I checked the code for any conflicting enums in the new code and it looked fine. My Question is what is wrong with the function call that compiler shows as erroneous? For your reference the function definition is: void Class::ShowStatus(const StatusSubsystem& eStatus) { QPalette palette; mStatus=eStatus;//store current Communication status of system if(eStatus==DISABLED) { //select red color for label, if it is to be shown disabled palette.setColor(QPalette::Window,QColor(Qt::red)); mLabel->setText("SYSTEM"); } else if(eStatus==ENABLED) { //select green color for label,if it is to be shown enabled palette.setColor(QPalette::Window,QColor(Qt::green)); mLabel->setText("SYSTEM"); } else if(eStatus==INCORRECT_FRAME) { //select yellow color for label,to show that it is sending incorrect frames palette.setColor(QPalette::Window,QColor(Qt::yellow)); mLabel->setText("SYSTEM(I)"); } //Set the color on the Label mLabel->setPalette(palette); } A strange side effect of this situation is it compiles when I cast all the calls to ShowStatus() as ShowStatus((StatusSubsystem)INCORRECT_FRAME); Though this removes any compilation error, but a strange thing happens. Though I make call to INCORRECT_FRAME above but in function definition it matches with ENABLED. How on earth is that possible? Its like while passing INCORRECT_FRAME by reference, it magically converts to ENABLED, which should be impossible. This is driving me nuts. Can you find any flaw in what I am doing? or is it something else? The application is made using C++,Qt-4.2.1 on RHEL4. Thanks.

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• Searching in XML using Xpath

  - by Sathish

  I have an XML file like below , using xpath and xnavigator how can get the Value of the supplied Tag Attribute for example if i supply RangeName i should get AssumptClient <Validations> <FieldInfo id="1"> <Name>OMID</Name> <Mandatory>Yes</Mandatory> <RangeName>AssumptOMID</RangeName> <DataType>int</DataType> <MaxLength>10</MaxLength> </FieldInfo> <FieldInfo id="2"> <Name>ClientName</Name> <Mandatory>Yes</Mandatory> <RangeName>AssumptClient</RangeName> <DataType>string</DataType> <MaxLength>50</MaxLength> </FieldInfo> <FieldInfo id="3"> <Name>OppName</Name> <Mandatory>Yes</Mandatory> <RangeName>AssumptProjectName</RangeName> <DataType>string</DataType> <MaxLength>50</MaxLength> </FieldInfo> <FieldInfo id="4"> <Name>OperatingGroup</Name> <Mandatory>Yes</Mandatory> <RangeName>AssumptOperatingGroup</RangeName> <DataType>string</DataType> <MaxLength>50</MaxLength> </FieldInfo> </Validations> for now i am using the below code XPathDocument doc; XPathNavigator nav; XPathExpression expr; XPathNodeIterator iterator; doc = new XPathDocument(strConfigFile); nav = doc.CreateNavigator(); expr = nav.Compile("/configuration/Validations/FieldInfo[RangeName='AssumptClient']"); iterator = nav.Select(expr); if (iterator.MoveNext()) { XPathNavigator nav2 = iterator.Current.Clone(); textBox1.Text = nav2.GetAttribute("RangeName", ""); }

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• [C++] Multiple inheritance from template class

  - by Tom P.

  Hello, I'm having issues with multiple inheritance from different instantiations of the same template class. Specifically, I'm trying to do this: template <class T> class Base { public: Base() : obj(NULL) { } virtual ~Base() { if( obj != NULL ) delete obj; } template <class T> T* createBase() { obj = new T(); return obj; } protected: T* obj; }; class Something { // ... }; class SomethingElse { // ... }; class Derived : public Base<Something>, public Base<SomethingElse> { }; int main() { Derived* d = new Derived(); Something* smth1 = d->createBase<Something>(); SomethingElse* smth2 = d->createBase<SomethingElse>(); delete d; return 0; } When I try to compile the above code, I get the following errors: 1>[...](41) : error C2440: '=' : cannot convert from 'SomethingElse *' to 'Something *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1> [...](71) : see reference to function template instantiation 'T *Base<Something>::createBase<SomethingElse>(void)' being compiled 1> with 1> [ 1> T=SomethingElse 1> ] 1>[...](43) : error C2440: 'return' : cannot convert from 'Something *' to 'SomethingElse *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast The issue seems to be ambiguity due to member obj being inherited from both Base< Something and Base< SomethingElse , and I can work around it by disambiguating my calls to createBase: Something* smth1 = d->Base<Something>::createBase<Something>(); SomethingElse* smth2 = d->Base<SomethingElse>::createBase<SomethingElse>(); However, this solution is dreadfully impractical, syntactically speaking, and I'd prefer something more elegant. Moreover, I'm puzzled by the first error message. It seems to imply that there is an instantiation createBase< SomethingElse in Base< Something , but how is that even possible? Any information or advice regarding this issue would be much appreciated.

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• Java program grading

  - by pasito15

  I've been working on this program for hours and I can't figure out how to get the program to actually print the grades from the scores Text file public class Assign7{ private double finalScore; private double private_quiz1; private double private_quiz2; private double private_midTerm; private double private_final; private final char grade; public Assign7(double finalScore){ private_quiz1 = 1.25; private_quiz2 = 1.25; private_midTerm = 0.25; private_final = 0.50; if (finalScore >= 90) { grade = 'A'; } else if (finalScore >= 80) { grade = 'B'; } else if (finalScore >= 70) { grade = 'C'; } else if (finalScore>= 60) { grade = 'D'; } else { grade = 'F'; } } public String toString(){ return finalScore+":"+private_quiz1+":"+private_quiz2+":"+private_midTerm+":"+private_final; } } this code compiles as well as this one import java.util.*; import java.io.*; public class Assign7Test{ public static void main(String[] args)throws Exception{ int q1,q2; int m = 0; int f = 0; int Record ; String name; Scanner myIn = new Scanner( new File("scores.txt") ); System.out.println( myIn.nextLine() +" avg "+"letter"); while( myIn.hasNext() ){ name = myIn.next(); q1 = myIn.nextInt(); q2 = myIn.nextInt(); m = myIn.nextInt(); f = myIn.nextInt(); Record myR = new Record( name, q1,q2,m,f); System.out.println(myR); } } public static class Record { public Record() { } public Record(String name, int q1, int q2, int m, int f) { } } } once a compile the code i get this which dosent exactly compute the numbers I have in the scores.txt Name quiz1 quiz2 midterm final avg letter Assign7Test$Record@4bcc946b Assign7Test$Record@642423 Exception in thread "main" java.until.InputMismatchException at java.until.Scanner.throwFor(Unknown Source) at java.until.Scanner.next(Unknown Source) at java.until.Scanner.nextInt(Unknown Source) at java.until.Scanner.nextInt(Unknown Source) at Assign7Test.main(Assign7Test.java:25)

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• Is there some way to make variables like $a and $b in regard to strict?

  - by Axeman

  In light of Michael Carman's comment, I have decided to rewrite the question. Note that 11 comments appear before this edit, and give credence to Michael's observation that I did not write the question in a way that made it clear what I was asking. Question: What is the standard--or cleanest way--to fake the special status that $a and $b have in regard to strict by simply importing a module? First of all some setup. The following works: #!/bin/perl use strict; print "\$a=$a\n"; print "\$b=$b\n"; If I add one more line: print "\$c=$c\n"; I get an error at compile time, which means that none of my dazzling print code gets to run. If I comment out use strict; it runs fine. Outside of strictures, $a and $b are mainly special in that sort passes the two values to be compared with those names. my @reverse_order = sort { $b <=> $a } @unsorted; Thus the main functional difference about $a and $b--even though Perl "knows their names"--is that you'd better know this when you sort, or use some of the functions in List::Util. It's only when you use strict, that $a and $b become special variables in a whole new way. They are the only variables that strict will pass over without complaining that they are not declared. : Now, I like strict, but it strikes me that if TIMTOWTDI (There is more than one way to do it) is Rule #1 in Perl, this is not very TIMTOWDI. It says that $a and $b are special and that's it. If you want to use variables you don't have to declare $a and $b are your guys. If you want to have three variables by adding $c, suddenly there's a whole other way to do it. Nevermind that in manipulating hashes $k and $v might make more sense: my %starts_upper_1_to_25 = skim { $k =~ m/^\p{IsUpper}/ && ( 1 <= $v && $v <= 25 ) } %my_hash ;` Now, I use and I like strict. But I just want $k and $v to be visible to skim for the most compact syntax. And I'd like it to be visible simply by use Hash::Helper qw<skim>; I'm not asking this question to know how to black-magic it. My "answer" below, should let you know that I know enough Perl to be dangerous. I'm asking if there is a way to make strict accept other variables, or what is the cleanest solution. The answer could well be no. If that's the case, it simply does not seem very TIMTOWTDI.

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