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• How well does Scala Perform Comapred to Java?

  - by Teja Kantamneni

  The Question actually says it all. The reason behind this question is I am about to start a small side project and want to do it in Scala. I am learning scala for the past one month and now I am comfortable working with it. The scala compiler itself is pretty slow (unless you use fsc). So how well does it perform on JVM? I previously worked on groovy and I had seen sometimes over performed than java. My Question is how well scala perform on JVM compared to Java. I know scala has some very good features(FP, dynamic lang, statically typed...) but end of the day we need the performance...

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• Are there any C++ tools that detect misuse of static_cast, dynamic_cast, and reinterpret_cast?

  - by chrisp451

  The answers to the following question describe the recommended usage of static_cast, dynamic_cast, and reinterpret_cast in C++: http://stackoverflow.com/questions/332030/when-should-static-cast-dynamic-cast-and-reinterpret-cast-be-used Do you know of any tools that can be used to detect misuse of these kinds of cast? Would a static analysis tool like PC-Lint or Coverity Static Analysis do this? The particular case that prompted this question was the inappropriate use of static_cast to downcast a pointer, which the compiler does not warn about. I'd like to detect this case using a tool, and not assume that developers will never make this mistake.

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• how to create a new variant in bjam

  - by steve jaffe

  I've tried reading the documentation but it is rather impenetrable so I'm hoping someone may have a simple answer. I want to define a new 'variant', based on 'debug', which just adds some macro definitions to the compiler command line, eg "-DSOMEMACRO". I think I may be able to do this as a "sub-variant" of debug, or else just define a new variant copying 'debug', but I'm not even sure where to do this. It looks like feature.jam in $BOOST_BUILD_DIR/build may be the place. Perhaps what I really want is simply a new 'feature' but it's still not clear to me exactly what I need to do and where, and I don't know if a 'feature' allows me to direct the build products to a different directory to the 'debug' build. Any suggestions will be appreciated. (In case you're wondering, I have to use bjam since it has been adopted as our corporate standard.)

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• About enumerations in Delphi and c++ in 64-bit environments

  - by sum1stolemyname

  I recently had to work around the different default sizes used for enumerations in Delphi and c++ since i have to use a c++ dll from a delphi application. On function call returns an array of structs (or records in delphi), the first element of which is an enum. To make this work, I use packed records (or aligned(1)-structs). However, since delphi selects the size of an enum-variable dynamically by default and uses the smallest datatype possible (it was a byte in my case), but C++ uses an int for enums, my data was not interpreted correctly. Delphi offers a compiler switch to work around this, so the declaration of the enum becomes {$Z4} TTypeofLight = ( V3d_AMBIENT, V3d_DIRECTIONAL, V3d_POSITIONAL, V3d_SPOT ); {$Z1} My Questions are: What will become of my structs when they are compiled on/for a 64-bit environment? Does the default c++ integer grow to 8 Bytes? Are there other memory alignment / data type size modifications (other than pointers)?

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• Which format does static library (*.lib) files use? Where can I find "Official" specifications of *.

  - by claws

  Just now I found that static libraries in *nix systems, in other words *.a libraries are nothing but archives of relocatables(*.o files) in ar fromat. What about static libraries(*.lib files) in windows? Which format are they in? I found an article: http://www.microsoft.com/msj/0498/hood0498.aspx which explains *.lib file structure. But Where can I find "Official" specifications of *.lib file structure/format? Other than ar.exe of mingw is there any tool from Microsoft which extracts relocatable objects of *.lib & *.a files? EDIT: I wonder why I'm unable to get to this question. If there are no official specifications. Then how does the compiler ('linker' to be more correct) writers work with *.LIB files?

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• Opening Large (24 GB) File In C

  - by zacaj

  I'm trying to read in a 24 GB XML file in C, but it won't work. I'm printing out the current position using ftell() as I read it in, but once it gets to a big enough number, it goes back to a small number and starts over, never even getting 20% through the file. I assume this is a problem with the range of the variable that's used to store the position (long), which can go up to about 4,000,000,000 according to http://msdn.microsoft.com/en-us/library/s3f49ktz%28VS.80%29.aspx, while my file is 25,000,000,000 bytes in size. A long long should work, but how would I change what my compiler(Cygwin/mingw32) uses or get it to have fopen64?

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• Visual C++ 2010 solution-wide macros with parameters

  - by OregonGhost

  I'm trying to compile some source code with Visual C++ 2010 Express. The code was written for GCC, and contains attributes like this: struct something { ... } __attribute__((packed)); Since this is not standard C++ syntax, Visual C++ doesn't recognize it. With this macro prior to the struct declaration, it works fine: #define __attribute__(p) But I don't want to alter the files. I created a new property sheet (GccCompat), and went to Preprocessor Definitions, and added the macro, like this: __attribute__(p) or like this: __attribute__(p)= But it doesn't work. It's simply not called. If I define just __attribute__ (without parameters) in the same location, the macro is correctly defined. Note that the command line that is generated looks fine (the macros with parameters are passed exactly the same as the ones without), but the compiler seems to ignore it. So, how can I globally define my macro with a parameter?

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• Why calling ISet<dynamic>.Contains() compiles, but throws an exception at runtime?

  - by Andrey Breslav

  Please, help me to explain the following behavior: dynamic d = 1; ISet<dynamic> s = new HashSet<dynamic>(); s.Contains(d); The code compiles with no errors/warnings, but at the last line I get the following exception: Unhandled Exception: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'System.Collections.Generic.ISet<object>' does not contain a definition for 'Contains' at CallSite.Target(Closure , CallSite , ISet`1 , Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1) at FormulaToSimulation.Program.Main(String[] args) in As far as I can tell, this is related to dynamic overload resolution, but the strange things are (1) If the type of s is HashSet<dynamic>, no exception occurs. (2) If I use a non-generic interface with a method accepting a dynamic argument, no exception occurs. Thus, it looks like this problem is related particularly with generic interfaces, but I could not find out what exactly causes the problem. Is it a bug in the compiler/typesystem, or legitimate behavior?

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• c99 goto past initialization

  - by R Samuel Klatchko

  While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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• Extract Generic types from extended Generic

  - by Brigham

  I'm trying to refactor a class and set of subclasses where the M type does extend anything, even though we know it has to be a subclass of a certain type. That type is parametrized and I would like its parametrized types to be available to subclasses that already have values for M. Is there any way to define this class without having to include the redundant K and V generic types in the parameter list. I'd like to be able to have the compiler infer them from whatever M is mapped to by subclasses. public abstract class NewParametrized<K, V, M extends SomeParametrized<K, V>> { public void someMethodThatTakesKAndV(K k1, V v1) { } } In other words, I'd like the class declaration to look something like: public class NewParametrized<M extends SomeParametrized<K, V>> { And K and V's types would be inferred from the definition of M.

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• Problem with array of elements of a structure type

  - by kobac

  I'm writing an app in Visual Studio C++ and I have problem with assigning values to the elements of the array, which is array of elements of structure type. Compiler is reporting syntax error for the assigning part of the code. Is it possible in anyway to assign elements of array which are of structure type? typedef struct { CString x; double y; } Point; Point p[3]; p[0] = {"first", 10.0}; p[1] = {"second", 20.0}; p[2] = {"third", 30.0};

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• How to insert an integer into a database through command prompt

  - by jpavlov

  I am trying to insert a integer into a database in C# using the code below, but everytime I run the compiler informs me that my integer is not a valid column "Invalid Column Name UserID" Does anyone have any insight on this? Thanks. Console.WriteLine("Please enter a new User Id"); string line = Console.ReadLine(); int UserID; if (int.TryParse(line, out UserID)) { Console.WriteLine(UserID); Console.ReadLine(); } //Prepare the command string string insertString = @"INSERT INTO tb_User(ID,f_Name, l_Name) VALUES (UserID,'Ted','Turner')";

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• How does compilation work with AOP?

  - by alee

  I need quick answer to a simple thing in AOP. If i have a code deployed at client side and i have written new aspects, which i want in the client side software. do i have to "recompile" complete software with "original" code and new "AOP" code? (with aop compiler)? i.e. do i need the source code of original program with source code of new AOP and compile 'em boht? P.S: I am asking in general, not being specific to any language.

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• Looking for marg_setValue fix in iPhoneOS

  - by John Smith

  I am trying to compile a library originally written for Cocoa. Things are good until it looks for the function marg_setValue(). It says there is a syntax error before char in marg_setValue(argumentList,argumentOffset,char,(char)lua_toboolean(state,luaArgument)); (it's talking about the third argument, not (char) ) I am trying to port LuaObjectiveCBridge to the iPhone. It has two choices, either using Runtime or Foundation. I have discovered there are some problems with foundation so I am trying runtime. But the compiler is not co-operating.

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• What should I do if a IOException is thrown?

  - by Roman

  I have the following 3 lines of the code: ServerSocket listeningSocket = new ServerSocket(earPort); Socket serverSideSocket = listeningSocket.accept(); BufferedReader in = new BufferedReader(new InputStreamReader(serverSideSocket.getInputStream())); The compiler complains about all of these 3 lines and its complain is the same for all 3 lines: unreported exception java.io.IOException; In more details, these exception are thrown by new ServerSocket, accept() and getInputStream(). I know I need to use try ... catch .... But for that I need to know what this exceptions mean in every particular case (how should I interpret them). When they happen? I mean, not in general, but in these 3 particular cases.

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• How to learn to program C the right way

  - by sfactor

  i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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• Using sys/socket.h functions on windows

  - by BSchlinker

  Hello, I'm attempting to utilize the socket.h functions within Windows. Essentially, I'm currently looking at the sample code at http://beej.us/guide/bgnet/output/html/multipage/clientserver.html#datagram. I understand that socket.h is a Unix function -- is there anyway I can easily emulate that environment while compiling this sample code? Does a different IDE / compiler change anything? Otherwise, I imagine that I need to utilize a virtualized Linux environment, which may be best anyways as the code will most likely be running in a UNIX environment. Thanks.

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• Optional structural typing possibilty in C++ or anyother language?

  - by ambhai

  In C++ how to tell compiler that Ogre::Vector3 IS_SAME_AS SomeOtherLIB::Vector3 ? I feel that.. in languages like c++ which are not structural typed but there are cases when it makes sense. Normally as game developer when working with 4+ libraries that provide sort or their own Vector3 implementation. The code is littered with ToOgre, ToThis, ToThat conversion function. Thats a lot of Float3 copying around which should not happen on first place. Is in C++ or any other languages where we dont have to convert (copying) from one type to another which is essentially the samething. But any solution in C++ as most of the good gamedevs libs are for c/c++.

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• 2-byte (UCS-2) wide strings under GCC

  - by Seva Alekseyev

  Hi all, when porting my Visual C++ project to GCC, I found out that the wchar_t datatype is 4-byte UTF-32 by default. I could override that with a compiler option, but then the whole wcs* (wcslen, wcscmp, etc.) part of RTL is rendered unusable, since it assumes 4-byte wide strings. For now, I've reimplemented 5-6 of these functions from scratch and #defined my implementations in. But is there a more elegant option - say, a build of GCC RTL with 2-byte wchar-t quietly sitting somewhere, waiting to be linked? The specific flavors of GCC I'm after are Xcode on Mac OS X, Cygwin, and the one that comes with Debian Linux Etch.

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• Should I use C++0x Features Now?

  - by svu2g

  With the official release of VS 2010, is it safe for me to start using the partially-implemented C++0x feature set in my new code? The features that are of interest to me right now are both implemented by VC++ 2010 and recent versions of GCC. These are the only two that I have to support. In terms of the "safety" mentioned in the first sentence: can I start using these features (e.g., lambda functions) and still be guaranteed that my code will compile in 10 years on a compiler that properly conforms to C++0x when it is officially released? I guess I'm asking if there is any chance that VC++ 2010 or GCC will end up like VC++ 6; it was released before the language was officially standardized and consequently allowed grossly ill-formed code to compile. After all, Microsoft does say that "10 is the new 6". ;)

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• Why aren't operator conversions implicitly called for templated functions? (C++)

  - by John Gordon

  I have the following code: template <class T> struct pointer { operator pointer<const T>() const; }; void f(pointer<const float>); template <typename U> void tf(pointer<const float>); void g() { pointer<float> ptr; f(ptr); tf(ptr); } When I compile the code with gcc 4.3.3 I get a message (aaa.cc:17: error: no matching function for call to ‘tf(pointer<float>&)’) indicating that the compiler called 'operator pointer<const T>' for the non-templated function f(), but didn't for the templated function tf(). Why and is there any workaround short of overloading tf() with a const and non-const version? Thanks in advance for any help.

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• Modifying reference member from const member function in C++

  - by Philipp

  I am working on const-correctness of my code and just wondered why this code compiles: class X { int x; int& y; public: X(int& _y):y(_y) { } void f(int& newY) const { //x = 3; would not work, that's fine y = newY; //does compile. Why? } }; int main(int argc, char **argv) { int i1=0, i2=0; X myX(i1); myX.f(i2); ... } As far as I understand, f() is changing the object myX, although it says to be const. How can I ensure my compiler complains when I do assign to y? (Visual C++ 2008) Thank a lot!

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• bridge methods explaination

  - by xdevel2000

  If I do an override of a clone method the compiler create a bridge method to guarantee a correct polymorphism: class Point { Point() { } protected Point clone() throws CloneNotSupportedException { return this; // not good only for example!!! } protected volatile Object clone() throws CloneNotSupportedException { return clone(); } } so when is invoked the clone method the bridge method is invoked and inside it is invoked the correct clone method. But my question is when into the bridge method is called return clone() how do the VM to say that it must invoke Point clone() and not itself again???

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• File IO, Handling CRLF

  - by aCuria

  Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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• How to make Visual C++ 9 not emit code that is actually never called?

  - by sharptooth

  My native C++ COM component uses ATL. In DllRegisterServer() I call CComModule::RegisterServer(): STDAPI DllRegisterServer() { return _Module.RegisterServer(FALSE); // <<< notice FALSE here } FALSE is passed to indicate to not register the type library. ATL is available as sources, so I in fact compile the implementation of CComModule::RegisterServer(). Somewhere down the call stack there's an if statement: if( doRegisterTypeLibrary ) { //<< FALSE goes here // do some stuff, then call RegisterTypeLib() } The compiler sees all of the above code and so it can see that in fact the if condition is always false, yet when I inspect the linker progress messages I see that the reference to RegisterTypeLib() is still there, so the if statement is not eliminated. Can I make Visual C++ 9 perform better static analysis and actually see that some code is never called and not emit that code?

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