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• DataSet binding problem

  - by Shaine

  I've got in-memory dataset with some table defined and I populate this table in a following way: for(...) ds.Fields.AddFieldsRow(++j, 0, heading, "Char", "", "", "Input", 0, "","",""); On the GUI I've got DataGridView bound to that table inside TabControl (bound through BindingSource). Very strange thing is happening: if I open tab pane with this grid and populate table with some data then I see changes in grid. On the other side if I'm at other tab, populate table, and then switch to tab with grid I've got following exception: "DataMember property 'Fields' cannot be found on the DataSource". In similar way I've got 2 tab panes with grid in each that are bound to the same datatable using different datasources and I open one of them, populate, see the changes, then switch to second tab and get crash. What am I missing?

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• How to call operator<< on "this" in a descendant of std::stringstream?

  - by romkyns

  class mystream : public std::stringstream { public: void write_something() { this << "something"; } }; This results in the following two compile errors on VC++10: error C2297: '<<' : illegal, right operand has type 'const char [10]' error C2296: '<<' : illegal, left operand has type 'mystream *const ' Judging from the second one, this is because what this points at can't be changed, but the << operator does (or at least is declared as if it does). Correct? Is there some other way I can still use the << and >> operators on this?

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• C++: Vector of objects vs. vector of pointers to new objects?

  - by metamemetics

  Hello, I am seeking to improve my C++ skills by writing a sample software renderer. It takes objects consisting of points in a 3d space and maps them to a 2d viewport and draws circles of varying size for each point in view. Which is better: class World{ vector<ObjectBaseClass> object_list; public: void generate(){ object_list.clear(); object_list.push_back(DerivedClass1()); object_list.push_back(DerivedClass2()); or... class World{ vector<ObjectBaseClass*> object_list; public: void generate(){ object_list.clear(); object_list.push_back(new DerivedClass1()); object_list.push_back(new DerivedClass2()); ?? Would be using pointers in the 2nd example to create new objects defeat the point of using vectors, because vectors automatically call the DerivedClass destructors in the first example but not in the 2nd? Are pointers to new objects necessary when using vectors because they handle memory management themselves as long as you use their access methods? Now let's say I have another method in world: void drawfrom(Viewport& view){ for (unsigned int i=0;i<object_list.size();++i){ object_list.at(i).draw(view); } } When called this will run the draw method for every object in the world list. Let's say I want derived classes to be able to have their own versions of draw(). Would the list need to be of pointers then in order to use the method selector (-) ?

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• [C] Read line from file without knowing the line length.

  - by ryyst

  Hi, I want to read in a file line by line, without knowing the line length before. Here's what I got so far: int ch = getc(file); int length = 0; char buffer[4095]; while (ch != '\n' && ch != EOF) { ch = getc(file); buffer[length] = ch; length++; } printf("Line length: %d characters.", length); I can now figure out the line length, but only for lines that are shorter than 4095 characters. Is there a better way to do this (I already used fgets() but got told it wasn't the best way)? --Ry

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• Reading in data from a file into an array

  - by Sam

  If I have an options file along the lines of this: size = 4 data = 1100010100110010 And I have a 2d size * size array that I want to populate the values in data into, what's the best way of doing it? To clarify, for the example I have I'd want an array like this: int[4][4] array = {{1,1,0,0}, {0,1,0,1}, {0,0,1,1}, {0,0,1,0}}. (Not real code but you get the idea). Size can be really be any number though. I'm thinking I'd have to read in the size, maloc an array and then maybe read in a string full of data then loop through each char in the data, cast it to an int and stick it in the appropriate index? But I really have no idea how to go about it, have been searching for a while with no luck. Any help would be cool! :)

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• character_set_filesystem not present in show variables

  - by Diego

  I'm a little worried about the absence of this variable when I execute the show variables command. This is what I get when I execute show variables like 'char%': character_set_client utf8 character_set_connection utf8 character_set_database utf8 character_set_results utf8 character_set_server utf8 character_set_system utf8 character_sets_dir /usr/share/mysql/charsets/ I wonder why this is happening. What does it mean? can I just add it to the my.cnf file? Thank you... Edit: Sorry, I recently noted that I didn't specify which variable we're talking about (though I said it in the title). The variable is character_set_filesystem. Thanks.

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• Understanding c++ block of code

  - by kotoko

  I was given a c++ main and have to code it so it works. I am having some trouble understanding the code as I am a bit new to cpp. Here is the code int main(int argc, char *argv[]) { Class::setAtribute("string"); Class(Class::CONSTANT) << "starting up..."; } Some questions: How can the first line work with no variables? Is it static? The second line is really strange for me, what I can make out is a Constructor that takes in a class constante and then prints it out somehow? If someone could explain me this bit of code it would be great! Thanks in advance.

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• c++ file bad bit

  - by user230911

  Hi, when I run this code, the open and seekg and tellg operation all success. but when I read it, it fails, the eof,bad,fail bit are 0 1 1. What can cause a file bad? thanks int readriblock(int blockid, char* buffer) { ifstream rifile("./ri/reverseindex.bin", ios::in|ios::binary); rifile.seekg(blockid * RI_BLOCK_SIZE, ios::beg); if(!rifile.good()){ cout<<"block not exsit"<<endl; return -1;} cout<<rifile.tellg()<<endl; rifile.read(buffer, RI_BLOCK_SIZE); **cout<<rifile.eof()<<rifile.bad()<<rifile.fail()<<endl;** if(!rifile.good()){ cout<<"error reading block "<<blockid<<endl; return -1;} rifile.close(); return 0; }

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• C++, Get text from a website, part 3

  - by pure841

  So, thanks for all the help guys, I am just have one last problem, I am putting the website source in a char var, and then reading the product title (I have gotten that), however it only works if I take part of the source, or only the html from one of the featured products on neweggs page. I think the program is crashing, because it doesnt know which title to pick when I need to get all three titles and put them into an array. Any ideas? Thanks. Here is the parser code: http://paste2.org/p/809045 Any solution is greatly appreciated.

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• Remove newline character while XML parsing

  - by Prashant

  Hi, I am facing a problem while XML parsing. I have an NSMutablestring currentElementValue that has newlines into it. It has been received as an XMl from a web source. Even when i am trying to remove newline charactersets of substring the first 3 char there is no effect on the string. What can be done here? Regards PC Code is (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if(!currentElementValue) currentElementValue = [[NSMutableString alloc] initWithString:string]; else { [currentElementValue substringFromIndex:3]; [currentElementValue stringByTrimmingCharactersInSet:[NSCharacterSet newlineCharacterSet]]; NSLog(@"Processing Value : %@ with length %d", currentElementValue,[currentElementValue length] ); }

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• Copy Constructor in C++

  - by user265260

  i have this code #include <iostream> using namespace std; class Test{ public: int a; Test(int i=0):a(i){} ~Test(){ cout << a << endl; } Test(const Test &){ cout << "copy" << endl; } void operator=(const Test &){ cout << "=" << endl; } Test operator+(Test& p){ Test res(a+p.a); return res; } }; int main (int argc, char const *argv[]){ Test t1(10), t2(20); Test t3=t1+t2; return 0; } Output: 30 20 10 Why isnt the copy constructor called here?

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• How to execute unknown functions from dynamic load libraries?

  - by activenightly

  It's easy to load functions from dynamic libraries when you know this function in design time. just do something like this: int (*fn)(int); l0 = dlopen("./libfoo.so", RTLD_LAZY); if (!l0) { fprintf(stderr, "l0 %s\n", dlerror()); return 1; } fn = (int (*)(int))dlsym(l0, "foo"); if ((error = dlerror()) != NULL) { fprintf(stderr, "fn:%s\n", error); return 1; } x=(*fn)(y); ... How to execute library function when it's unknown in design time? In runtime you have a function name and array of arguments pointers and array of arguments sizes: char* fn_name="foo"; int foo_argc; void* foo_argv[]; int foo_argv_size[]; In scripting language it's a piece a cake task, but how to implement this nicely in c++?

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• C pointer initialization and dereferencing, what's wrong here?

  - by randombits

  This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from integer without a cast I just want to print the value that the pointer n references. I'm dereferencing it in the printf() statement and I get a segmentation fault. Compiling this with gcc -o foo foo.c.

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• Excel VBA : Changing string in cells

  - by user1265125

  I have cells with data like these: ABCD123XYZ MPOP345MLU . . . . What I want to do is, to remove the 3rd and 4th character from all these cells, hence giving AB123XYZ MP345MLU How do I do this in VBA? I have no idea about this language, and if someone can guide me in the right direction, it'd be great :) I understand I have to: 1. Declare 2 string variables st1 and st2 2. Store data from cell A1 into the variable st1 3. Copy all but the 2nd and 3rd char into str2 4. Output Str2 into B1 5. Move to A2

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• Authenticating a SOAP service in Java (password security)

  - by user1686448

  I am writing an application, in Java, which needs to log in to a remote SOAP service (JIRA) prior to calling methods on that service. I have looked at examples of how to do this, for example http://www.j-tricks.com/1/post/2010/8/jira-soap-client.html, however I am concerned that I need to put the password in memory at some point. I've read that I should store the password as a char[] but still, I'm concerned about storing the password in the clear at all. How should I store the password used by my client to log into the SOAP service? And how should I read it and pass it to JIRA?

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• Data conversion from accelerometer

  - by mrigendra

  Hi all I am working on an accelerometer bma220 , and its datasheet says that data is in 2's complement form.So what i had to do was getting that 8 bit data in any 8 bit signed char and done. the bma220 have an 8 bit register of which first 6 bits are data and last two are zero. void properdata(int16_t *msgData) { printf("\nin proper data\n"); int16_t temp, i; for(i=0; i<3; i++) { temp = *(msgData + i); printf("temp = %d sense = %d\n", temp, sense); temp = temp >> 2; // only 6 bits data temp = temp / sense; //decimal value * .0625 = value in g printf("temp = %d\n", temp); } } in this program i am taking data in a unsigned variable msgdata and doing all the calculations on a signed variable. I just need to know if this is the correct way to convert data?

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• const keyword in Objective-c

  - by user392412

  int main(int argc, char *argv[]) { @autoreleasepool { const int x = 1; const NSMutableArray *array1 = [NSMutableArray array]; const NSMutableString *str1 = @"1"; NSString * const str2 = @"2"; // x = 2; compile error [array1 addObject:@"2"]; // ok // [str1 appendString:@"2"]; // runtime error // Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attempt to mutate immutable object with appendString:' // str2 = @"3"; compile error } } my Question is Why array1 addObject is legal and why str1 appendString is forbidden?

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• remove versioning on boost xml serialization

  - by cppanda

  hi, i just can't find a way to remove the version tracking from the boost xmlarchives. example <Settings class_id="0" tracking_level="0" version="1"> <px class_id="1" tracking_level="1" version="0" object_id="_0"> <TestInt>3</TestInt> <Resolution class_id="2" tracking_level="0" version="0"> <x>800</x> <y>600</y> </Resolution> <SomeStuff>0</SomeStuff> </px> </Settings> I want to get ride of the class_id="0" tracking_level="0" version="1" stuff, because for in this case i just don't need it and want a simple clean config like file code void serialize(Archive & ar, const unsigned int version) { ar & make_nvp("TestInt", TestInt); ar & make_nvp("Resolution", resolution); ar & make_nvp("SomeStuff", SomeStuff); } i found boost::serialization::track_never, but nowhere to use it

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• MySQLi String comparisons using keys

  - by asdasd

  I have a table with lets say 2 columns. id number, and value. Value is a string (var char). Lets say i have a number x, and a list of numbers a1, a2, a3, a4, a5..... where x is not in the list. All of these numbers correspond to a unique row in the table. I want to know if the string value for x in the table is contained in one of the string values for any table entry for a1, a2, a3, a4... Lets say i have these rows: x, aaa a1, bbb a2, ccc a3, ddd a4, aaabbbcc then i want somehow a confirmation that yes, the value for x is included in one of the values in my list of numbers (a4 contains x). I know i can do this in a couple queries and shove it down some PHP and get my answer. But can i do this with one query?

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• Why does this code crash?

  - by user146780

  The following code causes a stack overflow but I don't see why... int _tmain(int argc, _TCHAR* argv[]) { cout << "start"; char bmp[1024][768][3]; for (int p = 0; p < 9000; ++p) { for(int i = 0; i < 1024; ++i) { for(int j = 0; j < 768; ++j) { bmp[i][j][0] = 20; } } } cout << "Stop"; return 0; } Thanks

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• c++: how can i read a file line by line to a string type variable?

  - by ufk

  Hiya. I'm trying to read a file line by line to a string type variable using the following code: #include <iostream> #include <fstream> ifstream file(file_name); if (!file) { cout << "unable to open file"; exit(1); } string line; while (!file.eof()) { file.getline(line,256); cout<<line; } file.close(); it won't compile when I try to use String class, only when i use char file[256] instead. how can I get line by line into a string class? thanks!

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• C++ toLowerCase Function won't work - Access violation

  - by misaizdaleka

  Hi, I have a simple function which takes an array of characters as an argument, and converts all the characters to lower case. However, I get a weird access violation error. Here's the code: void toLower(char *rec) { int i=0; while (rec[i]!='\0') { if (rec[i]>='A' && rec[i]<='Z') rec[i]='a'+rec[i]-'A'; //this is where I get an error - assigning the //the value to rec[i] is the problem i++; } } Can you tell me what's my mistake? Thanks

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• Reading long lines from text file

  - by sonofdelphi

  I am using the following code for reading lines from a text-file. What is the best method for handling the case where the line is greater than the limit SIZE_MAX_LINE? void TextFileReader::read(string inFilename) { ifstream xInFile(inFilename.c_str()); if(!xInFile){ return; } char acLine[SIZE_MAX_LINE + 1]; while(xInFile){ xInFile.getline(acLine, SIZE_MAX_LINE); if(xInFile){ m_sStream.append(acLine); //Appending read line to string } } xInFile.close(); }

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• How do I get the size of the boost buffer

  - by Anonymous

  I am trying to make an asynchronised server in visual studio and I use boost::asio::async_read(m_socket, boost::asio::buffer(m_buffer), boost::bind(&tcp_connection::handle_read, shared_from_this(), boost::asio::placeholders::error)); to get the buffer to be put in m_buffer boost::array<char, 256> m_buffer; but how do I get the size of this thing, m_buffer? size() didn't work, end() didn't work.. Any help would be fantastic. Thanks in advance.

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• C# character counter when writing to new line

  - by Mike

  Basically i'm trying to read a really big text file and when the charecters of the line reach X amount write to a new line, but i can't seem to get the charecter count to work. Any help is appricated! using (FileStream fs = new FileStream(betaFilePath,FileMode.Open)) using (StreamReader rdr = new StreamReader(fs)) { while (!rdr.EndOfStream) { string betaFileLine = rdr.ReadLine(); int stringline = 0; if (betaFileLine.Contains("þTEMP")) { //sb.AppendLine(@"C:\chawkster\workfiles\New Folder\GEL_ALL_PRODUCTS_CONCORD2.DAT"); string checkline = betaFileLine.Length.ToString(); foreach (string cl in checkline) { stringline++; File.AppendAllText(@"C:\chawkster\workfiles\New Folder\GEL_ALL_PRODUCTS_CONCORD3.DAT", cl); if(stringline == 1200) { File.AppendAllText(@"C:\chawkster\workfiles\New Folder\GEL_ALL_PRODUCTS_CONCORD3.DAT","\n"); stringline = 0; } } } } foreach (string cl in checkline) Error 1 Cannot convert type 'char' to 'string'

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