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• Fix DB duplicate entries (MySQL bug)

  - by Silence

  I'm using MySQL 4.1. Some tables have duplicates entries that go against the constraints. When I try to group rows, MySQL doesn't recognise the rows as being similar. Example: Table A has a column "Name" with the Unique proprety. The table contains one row with the name 'Hach?' and one row with the same name but a square at the end instead of the '?' (which I can't reproduce in this textfield) A "Group by" on these 2 rows return 2 separate rows This cause several problems including the fact that I can't export and reimport the database. On reimporting an error mentions that a Insert has failed because it violates a constraint. In theory I could try to import, wait for the first error, fix the import script and the original DB, and repeat. In pratice, that would take forever. Is there a way to list all the anomalies or force the database to recheck constraints (and list all the values/rows that go against them) ? I can supply the .MYD file if it can be helpful.

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• How can I force the text go to the button of the panel?

  - by Roman

  At the moment I have the following code which works fine. label = new JLabel(panelLabel,SwingConstants.CENTER); outputPanel.add(label,BorderLayout.CENTER); I get the text in the center of the panel (in terms of the left-right position as well as in terms of the top-bottom). Now I want to set the position to the bottom (and center in terms of "left-right"). I tried to use SOUTH instead of the CENTER in the first line. Compiler does not complains but during the execution i get IllegalArgumentException: HorizontalAlignment. What is that?

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• How can I do these operations in C?

  - by Juan Antonio

  Hello, I'm converting some assembly code to C to be able to use it with the current compiler environment I have to work with. I've reached 2 operations I don't know how to translate to C. Anyone know how to do it? In both, offset is an unsigned 32-bit integer and shift is a signed integer value. C_FLAG is a bool. OP1: __asm { __asm mov ecx, shift __asm ror offset, cl } OP2: __asm { __asm bt dword ptr C_FLAG, 0 __asm rcr offset, 1 } Thank you very much for your expertise. P.S.: I'm not the original developer, nor I have seen many x86 assembly code...

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• C++: namespace conflicht between extern "C" and class member

  - by plaisthos

  Hi, I stumbled upon a rather exotic c++ namespace problem: condensed example: extern "C" { void solve(lprec * lp); } class A { public: lprec * lp; void solve(int foo); } void A::solve(int foo) { solve(lp); } I want to call the c funcition solve in my C++ member function A::solve. The compiler is not happy with my intents: error C2664: 'lp_solve_ilp::solve' : cannot convert parameter 1 from 'lprec *' to 'int' Is there something I can prefix the solve function? C::solve does not work

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• Problem with basic program using Boost Threads in c++

  - by Eternal Learner

  I have a simple program which creates and executes as thread using boost threads in c++. #include<boost/thread/thread.hpp> #include<iostream> void hello() { std::cout<<"Hello, i am a thread"<<std::endl; } int main() { boost::thread th1(&hello); th1.join(); } The compiler throws an error against the th1.join() line. It says " Multiple markers at this line - undefined reference to `boost::thread::join()' - undefined reference to `boost::thread::~thread()' "

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• When will YOU adopt C++0x?

  - by HighCommander4

  I'm particularly looking for input from managers of ongoing C++ projects: Have you already adopted C++0x? If so, what has your experience been like? If you haven't adopted C++0x yet, are you planning to? If so, what is your timeline (in rough terms)? Are there any obstacles that are holding you back from adopting C++0x? Perhaps you are waiting for your favourite compiler or IDE to catch up? For managers of open source projects: are you afraid that adopting C++0x will mean less developers who are willing/able to contribute because they don't know the new features? Or, on the other hand, do you think most developers have been eagerly awaiting C++0x, and and will jump at the opportunity to use it? Do you think C++0x is stable enough to be adopted by a large project?

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• Injecting a dependancy into a base class

  - by Jamie Dixon

  Hey everyone, I'm on a roll today with questions. I'm starting out with Dependency Injection and am having some trouble injecting a dependency into a base class. I have a BaseController controller which my other controllers inherit from. Inside of this base controller I do a number of checks such as determining if the user has the right privileges to view the current page, checking for the existence of some session variables etc. I have a dependency inside of this base controller that I'd like to inject using Ninject however when I set this up as I would for my other dependencies I'm told by the compiler that: Error 1 'MyProject.Controllers.BaseController' does not contain a constructor that takes 0 argument This makes sense but I'm just not sure how to inject this dependency. Should I be using this pattern of using a base controller at all or should I be doing this in a more efficient/correct way?

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• Using typedefs (or #defines) on built in types - any sensible reason?

  - by jb

  Well I'm doing some Java - C integration, and throught C library werid type mappings are used (theres more of them;)): #define CHAR char /* 8 bit signed int */ #define SHORT short /* 16 bit signed int */ #define INT int /* "natural" length signed int */ #define LONG long /* 32 bit signed int */ typedef unsigned char BYTE; /* 8 bit unsigned int */ typedef unsigned char UCHAR; /* 8 bit unsigned int */ typedef unsigned short USHORT; /* 16 bit unsigned int */ typedef unsigned int UINT; /* "natural" length unsigned int*/ Is there any legitimate reason not to use them? It's not like char is going to be redefined anytime soon. I can think of: Writing platform/compiler portable code (size of type is underspecified in C/C++) Saving space and time on embedded systems - if you loop over array shorter than 255 on 8bit microprocessor writing: for(uint8_t ii = 0; ii < len; ii++) will give meaureable speedup.

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• Masking a bit in C returning unexpected result

  - by Eamorr

  0x7F000000 is 0111 1111 0000 0000 0000 0000 0000 0000 in 32 bit binary. 0x01000058 is 0000 0001 0000 0000 0000 0000 0101 1000. When I AND the two numbers together I expect 0000 0001 0000 0000 0000 0000 0000 0000, but for some reason I get 0. Here is my code: #define MASK_binop 0x80000000 #define MASK_operation 0x7F000000 int instruction=atoi(line); if((MASK_binop & instruction)>0) printf("binop\n"); else if((MASK_operation & instruction)>0) printf("operation\n"); Each of the above comparisons keeps returning zero. Is it something to do with 32/64 bits? I'm using 64-bit compiler.

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• What's the best way to build software that doesn't require the newest glibc?

  - by ZorbaTHut

  I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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• Memory management for "id<ProtocolName> variableName" type properties

  - by Malakim

  Hi, I'm having a problem with properties of the following type: id<ProtocolName> variableName; ..... ..... @property (nonatomic, retain) id<ProtocolName> variableName; I can access and use them just fine, but when I try to call [variableName release]; I get compiler warnings: '-release' not found in protocol(s) Do I need to define a release method in the interface, or how do I release the memory reserved for the variable? Thanks!

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• C++: How to use types that have not been defined?

  - by Jen

  C++ requires all types to be defined before they can be used, which makes it important to include header files in the right order. Fine. But what about my situation: Bunny.h: class Bunny { ... private: Reference<Bunny> parent; } The compiler complains, because technically Bunny has not been completely defined at the point where I use it in its own class definition. This is not sufficient: class Bunny; class Bunny { ... private: Reference<Bunny> parent; } Apart from re-writing my template class Reference so it takes a pointer type (in which case I can use the forward declaration of Bunny), I don't know how to solve this. Any suggestions?

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• C/C++ usage of special CPU fetures

  - by b-gen-jack-o-neill

  Hi, I am curious, do new compilers use some extra features built into new CPUs such as MMX SSE,3DNow! and so? I mean, in original 8086 there was even no FPU, so compiler that old cannot even use it, but new compilers can, since FPU is part of every new CPU. So, does new compilers use new features of CPU? Or, it should be more right to ask, does new C/C++ standart library functions use new features? Thanks for answer.

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• How to identify multiple identical pairs in two vectors

  - by Sacha Epskamp

  In my graph-package (as in graph theory, nodes connected by edges) I have a vector indicating for each edge the node of origin from, a vector indicating for each edge the node of destination to and a vector indicating the curve of each edge curve. By default I want edges to have a curve of 0 if there is only one edge between two nodes and curve of 0.2 if there are two edges between two nodes. The code that I use now is a for-loop, and it is kinda slow: curve <- rep(0,5) from<-c(1,2,3,3,2) to<-c(2,3,4,2,1) for (i in 1:length(from)) { if (any(from==to[i] & to==from[i])) { curve[i]=0.2 } } So basically I look for each edge (one index in from and one in to) if there is any other pair in from and to that use the same nodes (numbers). What I am looking for are two things: A way to identify if there is any pair of nodes that have two edges between them (so I can omit the loop if not) A way to speed up this loop # EDIT: To make this abit clearer, another example: from <- c(4L, 6L, 7L, 8L, 1L, 9L, 5L, 1L, 2L, 1L, 10L, 2L, 6L, 7L, 10L, 4L, 9L) to <- c(1L, 1L, 1L, 2L, 3L, 3L, 4L, 5L, 6L, 7L, 7L, 8L, 8L, 8L, 8L, 10L, 10L) cbind(from,to) from to [1,] 4 1 [2,] 6 1 [3,] 7 1 [4,] 8 2 [5,] 1 3 [6,] 9 3 [7,] 5 4 [8,] 1 5 [9,] 2 6 [10,] 1 7 [11,] 10 7 [12,] 2 8 [13,] 6 8 [14,] 7 8 [15,] 10 8 [16,] 4 10 [17,] 9 10 In these two vectors, pair 3 is identical to pair 10 (both 1 and 7 in different orders) and pairs 4 and 12 are identical (both 2 and 8). So I would want curve to become: [1,] 0.0 [2,] 0.0 [3,] 0.2 [4,] 0.2 [5,] 0.0 [6,] 0.0 [7,] 0.0 [8,] 0.0 [9,] 0.0 [10,] 0.2 [11,] 0.0 [12,] 0.2 [13,] 0.0 [14,] 0.0 [15,] 0.0 [16,] 0.0 [17,] 0.0 (as I vector, I transposed twice to get row numbers).

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• Determine an object's class returned by a factory method (Error: function does not take 1 arguments

  - by tzippy

  I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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• Is it legal for a C++ reference to be NULL?

  - by BCS

  A while back I ran into a bug the looked something like this: void fn(int &i) { printf(&i == NULL ? "NULL\n" : "!NULL\n"); } int main() { int i; int *ip = NULL; fn(i); // prints !NULL fn(*ip); // prints NULL return 0; } More recently, I ran into this comment about C++ references: [References arguments make] it clear, unlike with pointers, that NULL is not a possible value. But, as show above, NULL is a possible value. So where is the error? In the language spec? (Unlikely.) Is the compiler in error for allowing that? Is that coding guide in error (or a little ambiguous)? Or am I just wandering into the minefield known as undefined behavior?

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• Constructing a function call in C

  - by 0x6adb015

  Given that I have a pointer to a function (provided by dlsym() for example) and a linked list of typed arguments, how can I construct a C function call with those arguments? Example: struct param { enum type { INT32, INT64, STRING, BOOL } type; union { int i32; long long i64; char *str; bool b; } value; struct param *next; }; int call_this(int (*function)(), struct param *args) { int result; /* magic here that calls function(), which has a prototype of f(int, long long, char *, bool); , when args consist of a linked list of INT32, INT64, STRING, BOOL types. */ return result; } The OS is Linux. I would like the solution to be portable across MIPS, PPC and x86 (all 32 bits) architecture, using GCC as the compiler. Thanks!

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• Using a class with const data members in a vector

  - by Max

  Given a class like this: class Foo { const int a; }; Is it possible to put that class in a vector? When I try, my compiler tells me it can't use the default assignment operator. I try to write my own, but googling around tells me that it's impossible to write an assignment operator for a class with const data members. One post I found said that "if you made [the data member] const that means you don't want assignment to happen in the first place." This makes sense. I've written a class with const data members, and I never intended on using assignment on it, but apparently I need assignment to put it in a vector. Is there a way around this that still preserves const-correctness?

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• const member functions can call const member functions only?

  - by Abhi

  Hi all. Do const member functions call only const member functions? class Transmitter{ const static string msg; mutable int size; public: void xmit() const{ size = compute(); cout<<msg; } private: int compute() const{return 5;} }; string const Transmitter::msg = "beep"; int main(){ Transmitter t; t.xmit(); return EXIT_SUCCESS; } If i dont make compute() a const, then the compiler complains. Is it because since a const member function is not allowed to modify members, it wont allow any calls to non-consts since it would mean that the const member function would be 'indirectly' modifying the data members?

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• Why Can't I import a UITableViewCell subclass ? That's weird....

  - by user320064

  It's like this, I created a UITableViewCell subclass called NewsItemCell, then I wanna use it in my FirstViewController.m, then I tried to import it, but the compiler keeps telling me this Below is my code, it is driving me mad, thank you if you can help. import "NewsItemCell.h" import "FirstViewController.h" @implementation FirstViewController @synthesize computers; (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"NewsItemCellIdentifier"; NewsItemcell *cell = (NewsItemcell *)[tableView dequeueReusableCellWithIdentifier: CellIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"NewsItemCell" owner:self options:nil]; for (id oneObject in nib) if ([oneObject isKindOfClass:[NewsItemcell class]]) cell = (NewsItemcell *)oneObject; } NSUInteger row = [indexPath row]; NSDictionary *rowData = [self.computers objectAtIndex:row]; cell.newsTitle.text = [rowData objectForKey:@"Color"]; cell.newsDate.text = [rowData objectForKey:@"Name"]; return cell; } Jason

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• Will Algorithm written in OCaml compiled from C be Faster than Algorithm written in Pure C code?

  - by Ole Jak

  So I have some cool Image Processing algorithm. I have written it in OCaml. It performs well. I now I can compile it as C code with such command ocamlc -output-obj -o foo.c foo.ml (I have a situation where I am not alowed to use OCaml compiler to bild my programm for my arcetecture, I can use only specialy modified gcc. so I will compile that programm with sometyhing like gcc -L/usr/lib/ocaml foo.c -lcamlrun -lm -lncurses and Itll run on my archetecture.) I want to know in general case will my OCaml code compiled into C run faster than algorithm implemented in pure C?

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• Quickly generate junk data of certain size in Javascript

  - by user1357607

  I am writing an upload speed test in Javascript. I am using Jquery (and Ajax) to send chunks of data to a server in order to time how long it takes to get a response. This should, in theory give an estimation, of the upload speed. Of course to cater for different bandwidths of the user I sequentially upload larger and larger amounts of junk data until a threshold duration is reached. Currently I generate the junk data using the following function, however, it is very slow when generation megabytes of data. function generate_random_data(size){ var chars = "abcdefghijklmnopqrstuvwxyz"; var random_data = ""; for (var i = 0; i < size; i++){ var random_num = Math.floor(Math.random() * char.length); random_data = random_data + chars.substring(random_num,random_num+1); } return random_data; Really all I am doing is generating a chunk of bytes to send to the server, however, this is the only way I could find out how in Javascript. Any help would be appreciated.

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• How to pass a class method as an argument for another function in C++ and openGL?

  - by tsubasa

  I know this thing works: void myDisplay() { ... } int main() { ... glutDisplayFunc(myDisplay) ... } so I tried to include myDisplay() function to a class that I made. Because I want to overload it in the future with a different class. However, the compiler complains that argument of type 'void (ClassBlah::)()' does not match 'void(*)()' . Here is the what I try to make: class ClassBlah { .... void myDisplay() .... } ...... int main() { ... ClassBlah blah glutDisplayFunc(blah.myDisplay) ... } Does anybody knows how to fix this problem? Many thanks.

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• How to avoid "incomplete implementation" warning in partial base class

  - by garph0

  I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: Incomplete implementation of class Base Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

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• What could possibly cause this error(when declaring an object inside a class) ? //noobie question

  - by M4design

  I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info' I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. Thanks. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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