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• Objective C LValue required as unary '&' operand

  - by Bob

  Hello! In my code, I get this error when I try to get a pointer to my class property. (I wrote a small *.OBJ file translator in Python, discarding the normals) CODE: //line: line of text const char *str = [line UTF8String]; Point3D *p1, *p2, *p3; p1 = [Point3D makeX:0 Y:0 Z:0]; p2 = [Point3D makeX:0 Y:0 Z:0]; p3 = [Point3D makeX:0 Y:0 Z:0]; sscanf(str, "t %f,%f,%f %f,%f,%f %f,%f,%f",(&[p1 x]),&([p1 y]),&([p1 z]),&([p2 x]),&([p2 y]),&([p2 z]),&([p3 x]),&([p3 y]),&([p3 z])); Triangle3D *tri = [Triangle3D make:p1 p2:p2 p3:p3];

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• How do I use "this" in a member function?

  - by Peter Stewart

  I've written a member function of class Node to read a tree of Nodes in postfix order. It will be called by the Node instance which is the root node of the tree. So: N.postfix(); these appear to be illeagal: *this->left.postfix(); *this->right.postfix(); What is the proper way to do this? class Node { public: const char *cargo; int depth; Node *left; Node *right void Node::postfix() { if (this==__nullptr) { return; } else { *this->left.postfix(); *this->right.postfix(); out<<*this->cargo<<"\n"; return; } };

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• RSA encrypted data block size

  - by calccrypto

  how do you store an rsa encrypted data block? the output might be significantly greater than the original input data block size, and i dont think people waste memory by padding bucket loads of 0s in front of each data block. besides, how would they be removed? or is each block stored on new lines within the file? if that is the case, how would you tell the difference between legitimate new line and a '\n' char written into the file? what am i missing? im writing the "write to file" part in python, so maybe its one of the differences between: open(file,'w') open(file,'w+b') open(file,'wb') that i dont know. or is it something else?

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• How to count the letters in a text with Javascript?

  - by Doguhanca

  I am currently trying to write a ''web application'' that has a simple text area inside, in which I want the letters of the text written to be pointed out. For example, if I write: ''How old are you? I am 19 years old'' I need a code to tell me how many 'A's and 'Y's and 'D's (and all letters of the alphabet from 0-26) are used in this sentence when I press a button on a HTML/ CSS page. Could you please tell me what I must write into my .JS file and what I should write into my .HTML file to do this with a click of a button when something is written in the ? I hope my explanation was detailed enough. Thanks! Edit (I'm very sorry for the problems I caused) - What I have done so far looks like this: HTML: <link rel="stylesheet" type="text/css" href="theme.css"> <meta charset="utf-8"> <script src="test.js" type="text/javascript"></script> <div class='header'> Al.Fa.Be </div> <div class='yaz'> <textarea></textarea> </div> <div class='description'> <a href='http://www.google.com'>Ara</a> </div> <div class='description2'> <input id="clickMe" type="button" value="Hesapla" onclick="doFunction();" /> </div> CSS: body{ background:white; } selection{ background:#CCC; } #clickMe{ background:#CCC; border:1px solid #333; } .header{ font-size:70px; font-weight:bold; font-family:Arial; color:#333; margin-left:580px; padding-top:200px; } textarea{ width:1210px; height:40px; color:black; margin-top:20px; margin-left:100px; padding-left:10px; padding-top:10px; font-size:18px; font-family:Arial; } .description{ background:#f2f2f2; padding:6px; width:50px; text-align:center; border:1px solid #ddd; font-family:Arial; margin-left:620px; margin-top:20px; font-size:14px; } .description a{ color:#555; text-decoration:none; } .description2{ background:#f2f2f2; padding:6px; width:60px; text-align:center; border:1px solid #ddd; font-family:Arial; margin-left:750px; margin-top:-30px; font-size:14px; } .description2 a{ color:#555; text-decoration:none; } .yaz{ color:white; } Javascript: // Input name. Count number of alphabets a-z class program                                                          {     public static void main(String[] args)     {         String name = args[0];         int count[] = new int[29];         int i,p;         int n = name.length();         name = name.toUpperCase();         char c;         for (i=0; i<29; i++)         {             count[i] = 0;           }         for (i=0; i<n; i++)         {             c = name.charAt(i);             p = (int) c;             count[p-65]++;         }         for (i=0; i<29 ; i++)         {             if (count[i] >0)             {                 System.out.println((char)(i+65) + " occurs " + count[i] + " times");             }         }     } }

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• Creating ostream manipulators for a specific class

  - by petersohn

  I have a class that is derived from ostream: class my_ostream: public std::ostream { // ... } I want to make a manipulator (for example do_something), that works specifically to this class, like this: my_ostream s; s << "some text" << do_something << "some more text"; I did the following: std::ostream &do_something(std::ostream &os) { my_ostream *s = dynamic_cast<my_ostream*>(&os); if (s != NULL) { // do something } return os; } This works, but is rather ugly. I tried the following: my_ostream &do_something(my_ostream &s) { // do something return s; } This doesn't work. I also tried another approach: class my_ostream: public std::ostream { // ... my_ostream &operator<<(const do_something & x) { // do something return *this; } } This still doesn't work.

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• strange results with /fp:fast

  - by martinus

  We have some code that looks like this: inline int calc_something(double x) { if (x > 0.0) { // do something return 1; } else { // do something else return 0; } } Unfortunately, when using the flag /fp:fast, we get calc_something(0)==1 so we are clearly taking the wrong code path. This only happens when we use the method at multiple points in our code with different parameters, so I think there is some fishy optimization going on here from the compiler (Microsoft Visual Studio 2008, SP1). Also, the above problem goes away when we change the interface to inline int calc_something(const double& x) { But I have no idea why this fixes the strange behaviour. Can anyone explane this behaviour? If I cannot understand what's going on we will have to remove the /fp:fastswitch, but this would make our application quite a bit slower.

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• C++0x, How do I expand a tuple into variadic template function arguments?

  - by Gustaf

  Consider the case of a templated function with variadic template arguments: template<typename Tret, typename... T> Tret func(const T&... t); Now, I have a tuple t of values. How do I call func() using the tuple values as arguments? I've read about the bind() function object, with call() function, and also the apply() function in different some now-obsolete documents. The GNU GCC 4.4 implementation seems to have a call() function in the bind() class, but there is very little documentation on the subject. Some people suggest hand-written recursive hacks, but the true value of variadic template arguments is to be able to use them in cases like above. Does anyone have a solution to is, or hint on where to read about it?

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• fgets, sscanf, and writing to arrays

  - by alldavidsluck

  beginner question here, I haven't been able to find examples that relate. I'm working on a C program that will take integer input from stdin using fgets and sscanf, and then write it to an array. However, I'm not sure how to make fgets write to the array. #define MAXINT 512 char input[MAXINT] int main(void) { int i; int j; int count=0; int retval; while (1==1) { fgets(input, MAXINT[count], stdin); retval = sscanf(input, "%d", &i); if (retval == 1) { count = count++; } else if (retval != 1) { break; } } Would I simply put fgets in a for loop? or is it more complicated than that?

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• Usage of atoi in the c language

  - by maddy

  I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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• Multidimensional Array Initialization: Any benefit from Threading?

  - by Alan

  say I have the following code: char[5][5] array; for(int i =0; i < 5; ++i) { for(int j = 0; j < 5; ++i) { array[i][j] = 'X'; } } Would there be a benefit for initializing each row in this array in a separate thread? Imagine instead of a 5 by 5 array, we have a 10 by 10? n x n? Also, this is done once, during application startup.

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• Object to Network serialization - with an existing protocol

  - by cpf

  I'm writing a client for a server program written in C++. As is not unusual, all the networking protocol is in a format where packets can be easily memcopied into/out of a C++ structure (1 byte packet code, then different arrangements per packet type). I could do the same thing in C#, but is there an easier way, especially considering lots of the data is fixed-length char arrays that I want to play with as strings? Or should I just suck it up and convert types as needed? I've looked at using the ISerializable interface, but it doesnt look as low level as is required.

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• reading a file that doesn't exist

  - by John

  Hi, I have got a small program that prints the contents of files using the system call - read. unsigned char buffer[8]; size_t offset=0; size_t bytes_read; int i; int fd = open(argv[1], O_RDONLY); do{ bytes_read = read(fd, buffer, sizeof(buffer)); printf("0x%06x : ", offset); for(i=0; i<bytes_read; ++i) { printf("%c ", buffer[i]); } printf("\n"); offset = offset + bytes_read; }while(bytes_read == sizeof(buffer)); Now while running I give a file name that doesn't exist. It prints some kind of data mixed with environment variables and a segmentation fault at the end. How is this possible? What is the program printing? Thanks, John

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• C++ conditional compilation

  - by Shaown

  I have the following code snippet #ifdef DO_LOG #define log(p) record(p) #else #define log(p) #endif void record(char *data){ ..... ..... } Now if I call log("hello world") in my code and DO_LOG isn't defined, will the line be compiled, in other words will it eat up the memory for the string "hello world"? P.S. There are a lot of record calls in the program and it is memory sensitive, so is there any other way to conditionally compile so that it only depends on the #define DO_LOG? Thanks in advance.

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• assignment vs std::swap and merging and keeping duplicates in seperate object

  - by rubenvb

  Say I have two std::set<std::string>s. The first one, old_options, needs to be merged with additional options, contained in new_options. I can't just use std::merge (well, I do, but not only that) because I also check for doubles and warn the user about this accordingly. To this effect, I have void merge_options( set<string> &old_options, const set<string> &new_options ) { // find duplicates and create merged_options, a stringset containing the merged options // handle duplicated the way I want to // ... old_options = merged_options; } Is it better to use std::swap( merged_options, old_options ); or the assignment I have? Is there a better way to filter duplicates and return the merged set than consecutive calls to std::set_intersection and std::set_union to detect dupes and merge the sets? I know it's slower than one traversal and doing both at once, but these sets are small (performance is not critical) and I trust the Standard more than I trust myself.

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• incorrect variable value outside main()

  - by cru3l

  i have this code #import <Foundation/Foundation.h> int testint; NSString *teststring; int Test() { NSLog(@"%d",testint); NSLog(@"%@",teststring); } int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; testint = 5; NSString *teststring = [[NSString alloc] initWithString:@"test string"]; Test(); [pool drain]; return 0; } in output i have: 5 (null) why Test function doesn't see correct teststring value? What should I do, to have correct "test string" in output?

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• What system does before launching iPhone app's main() function?

  - by Eonil

  My app takes too much time to loading. So I put a NSLog in main() function like this to measure loading time from first: int main(int argc, char *argv[]) { NSLog(@"main"); NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, nil); [pool release]; return retVal; } But, the log displayed at really later time. Default.png displayed about 5 seconds, all loading process completed in 1~2 seconds after log appeared. What's happening before executing main() function on iPhone app?

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• <function> referenced from; symbol(s) not found.

  - by jfm429

  I have a piece of C code that is used from a C++ function. At the top of my C++ file I have the line: #include "prediction.h" In prediction.h I have this: #ifndef prediction #define prediction #include "structs.h" typedef struct { double estimation; double variance; } response; response runPrediction(int obs, location* positions, double* observations, int targets, location* targetPositions); #endif I also have prediction.c, which has: #include "prediction.h" response runPrediction(int obs, location* positions, double* observations, int targets, location* targetPositions) { // code here } Now, in my C++ file (which as I said includes prediction.h) I call that function, then compile (through Xcode) I get this error: "runPrediction(int, location*, double*, int, location*)", referenced from: mainFrame::respondTo(char*, int)in mainFrame.o ld: symbol(s) not found collect2: ld returned 1 exit status prediction.c is marked for compilation for the current target. I don't have any problems with other .cpp files not being compiled. Any thoughts here?

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• parsing/matching string occurrence in C

  - by David

  I have the following string: const char *str = "\"This is just some random text\" 130 28194 \"Some other string\" \"String 3\"" I would like to get the the integer 28194 of course the integer varies, so I can't do strstr("20194"). So I was wondering what would be a good way to get that part of the string? I was thinking to use #include <regex.h> which I already have a procedure to match regexp's but not sure how the regexp in C will look like using the POSIX style notation. [:alpha:]+[:digit:] and if performance will be an issue. Or will it be better using strchr,strstr? Any ideas will be appreciate it

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• Using .dll methods to load data from file in C# code

  - by Espinas.iss

  I want to use in C# these methods: * int LibRaw::open_datastream(LibRaw_abstract_datastream *stream) * int LibRaw::open_file(const char *rawfile) * int LibRaw::open_buffer(void *buffer, size_t bufsize) * int LibRaw::unpack(void) * int LibRaw::unpack_thumb(void) that are stored in a libraw.dll. These functions one by one load data from file... I've been reading about P/Invoke but i'm not sure how to invoke them. Can anyone show me an example how to use all of these functions together in C# to load file (raw image stored in folder) or just how to PIvoke one of them. Thanx!

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• CryptGenRandom to generate asp.net session id

  - by DoDo

  Hi! does anyone have working example of CryptGenrRandom class to generate session id (need to use in my iis module). HCRYPTPROV hCryptProv; BYTE pbData[16]; if(CryptAcquireContext( &hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { if(CryptGenRandom(hCryptProv, 8, pbData)) { std::string s(( const char *) pbData); printf(s.c_str()); } else { MyHandleError("Error during CryptGenRandom."); } } else { MyHandleError("Error during CryptAcquireContext!\n"); } i tried this code but, its not working quite well (i get it from msdn) and this example don't work for me ( http://www.codeproject.com/KB/security/plaintextsessionkey.aspx ) so if anyone know how to generate sessionid using this class plz let me know tnx anyway!

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• c, pass awk syntax as argument to execl

  - by Skuja

  I want to run following command in c to read systems cpu and memory usage: ps aux|awk 'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}' I am trying to pass it to execl command and after that read its output: execl("/bin/ps", "/bin/ps", "aux|awk", "'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}'",(char *) 0); but in terminal i am getting following error: ERROR: Unsupported option (BSD syntax) I would like to know how to properly pass awk as argument to execl?

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• How to build up a lookup table in microcontroller?

  - by GiGi

  Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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• how to parse from command line arguements in yacc ?

  - by user205688

  how to parse from command line arguements in yacc ? of course i undefined input in both lex & yacc and then wrote int input(void) { printf("in input\n:"); char c; if(target > limit) return 0; if((c = target[0][offset++]) != '\0') return (c); target++; offset =0; return (' '); } where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.

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• File in binary form

  - by Abhi

  Dear All I want to write data into the file in binary form. I was trying using the mentioned below FILE *fp = fopen("binaryoutput.rgb888", "ab+"); for(int m=0; m<height; m++) { for (int n=0; n< width; n++) { temp = (pOutputImg+m*3+n*3); // here temp is a pointer to a unsigned char fprintf(fp,"%u",*temp); } } fclose(fp); I am able to get data which is strored at pOutputImg but not in binary form. Can anyone guide me the correct step.. Thanks in advance

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• Reallocating memory via "new" in C++

  - by BSchlinker

  Quick question regarding memory management in C++ If I do the following operation: pointer = new char [strlen(someinput_input)+1]; And then perform it again, with perhaps a different result being returned from strlen(someinput_input). Does this result in memory being left allocated from the previous "new" statement? IE, is each new statement receiving another block of HEAP memory from the OS, or is it simply reallocating? Assuming I do a final delete pointer[]; will that deallocate any and all memory that I ever allocated via new to that pointer? Thanks

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