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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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  • C String input confusion

    - by ahref
    C really isn't my strong point and after reading 3 chapters of a book on the subject and spending ages trying to get stuff working it just doesn't: #include <stdio.h> char *a,*b; int main( ) { char input[10]; fgets(input,sizeof input, stdin); a = input; fgets(input,sizeof input, stdin); b = input; printf("%s : %s",a,b); } I've isolated the problem from my main project. This code is meant to read in two strings and then print them however it seems to be setting a and b to point to input. Sample output from this code when A and B are entered is(don't worry about the \n's i can remove them): A B B : B How do i store the value of input in another variable eg. a or b so that in the above case A B A : B Is output? Thanks

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  • Question about C Pointers (just learning)

    - by Mike
    I am curious as to why this is an error and what the error message means. Here is some code. int *x[] = {"foo", "bar", "baz"}; int *y[] = {"foo", "bar", "baz"}; x = y; I try to compile and I get this: error: incompatible types when assigning to type ‘char [3]’ from type ‘char *’ Question #1 why is this an error? and Question #2 why are the types different? Thanks for you help.

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  • c: memory allocation (what's going on)

    - by facha
    Hi, everyone Please take a look at this piece of code. I'm allocating one byte for the first variable and another byte for the second one. However, it seems like the compiler allocates more (or I'm missing something). The program outputs both strings, even though their length is more the one byte. void main() { char* some1 = malloc(1); sprintf(some1,"cool"); char* some2 = malloc(1); sprintf(some2,"face"); printf("%s ",some1); printf("%s\n",some2); } Please, could anyone spot some light on what's going on when memory is being allocated.

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  • Scala, make my loop more functional

    - by Pengin
    I'm trying to reduce the extent to which I write Scala (2.8) like Java. Here's a simplification of a problem I came across. Can you suggest improvements on my solutions that are "more functional"? Transform the map val inputMap = mutable.LinkedHashMap(1->'a',2->'a',3->'b',4->'z',5->'c') by discarding any entries with value 'z' and indexing the characters as they are encountered First try var outputMap = new mutable.HashMap[Char,Int]() var counter = 0 for(kvp <- inputMap){ val character = kvp._2 if(character !='z' && !outputMap.contains(character)){ outputMap += (character -> counter) counter += 1 } } Second try (not much better, but uses an immutable map and a 'foreach') var outputMap = new immutable.HashMap[Char,Int]() var counter = 0 inputMap.foreach{ case(number,character) => { if(character !='z' && !outputMap.contains(character)){ outputMap2 += (character -> counter) counter += 1 } } }

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  • Casting a Calculated Column in a MySQL view.

    - by Chris Brent
    I have a view that contains a calculated column. Is there are a way to cast it as a CHAR or VARCHAR rather than a VARBINARY ? Obviously, I have tried using CAST(... as CHAR) but it gives an error. Here is a simple replicable example. CREATE VIEW view_example AS SELECT concat_ws('_', lpad(9, 3,'0'), lpad(1,3,'0'), date_format(now(),'%Y%m%d%H%i%S')) AS calculated_field_id; This is how my view is created: describe view_example; +---------------------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------------------+---------------+------+-----+---------+-------+ | calculated_field_id | varbinary(27) | YES | | NULL | | +---------------------+---------------+------+-----+---------+-------+ select version(); +-----------------------+ | version() | +-----------------------+ | 5.0.51a-community-log | +-----------------------+

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  • Storing objects in STL vector - minimal set of methods

    - by osgx
    Hello What is "minimal framework" (necessary methods) of object, which I will store in STL <vector>? For my assumptions: #include <vector> #include <cstring> using namespace std; class Doit { private: char *a; public: Doit(){a=(char*)malloc(10);} ~Doit(){free(a);} }; int main(){ vector<Doit> v(10); } gives *** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0804b008 *** Aborted and in valgrind: malloc/free: 2 allocs, 12 frees, 50 bytes allocated.

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  • Freeing a character pointer returns error

    - by Kraffs
    I'm trying to free a character pointer after having used it but it returns a strange error. The error says: "_CrtDbgREport: String too long or IO Error" The debugger itself returns no errors while compiling. The code currently looks like this: void RespondToUser(SOCKET client, SOCKET server) { char buffer[80]; char *temp = malloc(_scprintf("HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME)); sprintf(temp, "HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME); send(client, temp, strlen(temp), 0); closesocket(client); free(temp); ListenToUsers(server); } The problem only occurs when I try to free the temp pointer from the memory and not otherwise. What might be causing this?

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  • int[] to string c#

    - by Robin Webdev
    Hi I'm developing an client application in C# and the server is written in c++ the server uses: inline void StrToInts(int *pInts, int Num, const char *pStr) { int Index = 0; while(Num) { char aBuf[4] = {0,0,0,0}; for(int c = 0; c < 4 && pStr[Index]; c++, Index++) aBuf[c] = pStr[Index]; *pInts = ((aBuf[0]+128)<<24)|((aBuf[1]+128)<<16)|((aBuf[2]+128)<<8)|(aBuf[3]+128); pInts++; Num--; } // null terminate pInts[-1] &= 0xffffff00; } to convert an string to int[] in my c# client i recieve: int[4] { -14240, -12938, -16988, -8832 } How do I convert the array back to an string? I don't want to use unsafe code (e.g. pointers) Any of my tries resulted in unreadable strings.

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  • Function argument treated as undeclared

    - by Mikulas Dite
    I've prepared this simple example which is not working for me #include <stdio.h> #include <stdlib.h> FILE *fp; char filename[] = "damy.txt"; void echo (char[] text) { fp = fopen(filename, "a"); fwrite(text, 1, strlen(text), fp); fclose(fp); printf(text); } int main () { echo("foo bar"); return 0; } It's supposed to write both to command window and to file. However, this gives compilation error - the text used in echo() is not declared. Does c need another declaration of the variable?

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  • c++: truth assignment warning with arguments?

    - by John
    I use the following to work with arguments in my programs, but it seems to just hand me a warning (just a warning): "warning: suggest parentheses around assignment used as truth value" The beginning of the code is as follows: enum{OPT_DISP_H = 0x2, OPT_DISP_W = 0x1}; int main(int argc, char *argv[]) { int opt = 0x00; char c; while((++argv)[0] && argv[0][0]=='-'){ while(c =* ++argv[0]) switch(c){ case 'h': opt |= OPT_DISP_H; break; //etc.. The while(c =* ++argv[0]) part being where the warning persists. The code works fine, but what does this warning mean opposed to what is used? I think the code is c = *++argv[0], using the pointer. So why does the single = work and what is really recommended to be used?

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  • Function naming: sendCharacter or receiveCharacter?

    - by bobobobo
    I'm trying to name a function that runs when a character is received by the object. For the caller, it should be named sendCharacter, so that it can call: object->sendCharacter( character ) ; That looks nice for the caller.. but for the receiver, it implements a method /// Called when this object is do something /// with a character /// from the caller void sendCharacter( char c ) ; So for the recipient class, it looks like this method will actually send a character out, not receive one. So then, I could call the function receiveCharacter /// Called when this object is do something /// with a character /// from the caller void receiveCharacter( char c ) ; But now the caller does this: object->receiveCharacter( character ) ; Which just looks odd. How can I better name this function?

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  • strenge exception phenomenon in win7

    - by Level 2
    Hello all, I spot some interesting artcles about exception handle in codeproject http://www.codeproject.com/KB/cpp/seexception.aspx after reading, I decided to do some experiment. The first time I try to excute the following code char *p; p[0] = 0; The program died without question. But After serveral time I execute the same problem binary code. It magically did fine. even the following code is doing well. any clue or explain? char *p p[1000] = 'd'; cout<<p[1000]<<endl; my os is windows 7 64bit and compiler is vs2008 rc1.

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  • reading unicode

    - by user121196
    I'm using java io to retrieve text from a server that might output character such as é. then output it using System.err, they turn out to be '?'. I am using UTF8 encoding. what's wrong? int len=0; char[]buffer=new char[1024]; OutputStream os = sock.getOutputStream(); InputStream is = sock.getInputStream(); os.write(query.getBytes("UTF8"));//iso8859_1")); Reader reader = new InputStreamReader(is, Charset.forName("UTF-8")); do{ len = reader.read(buffer); if (len0) { if(outstring==null)outstring=new StringBuffer(); outstring.append(buffer,0,len); } }while(len0); System.err.println(outstring);

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  • strftimedoesnt display year correctly

    - by paultop6
    Hi guys, i have the following code below: const char* timeformat = "%Y-%m-%d %H:%M:%S"; const int timelength = 20; char timecstring[timelength]; strftime(timecstring, timelength, timeformat, currentstruct); cout << "timecstring is: " << timecstring << "\n"; currentstruct is a tm*. The cout is giving me the date in the correct format, but the year is not 2010, but 3910. I know there is something to do with the year cound starting at 1900, but im not sure how to get strftime to recognise this and not add 1900 to the value of 2010 that is there, can anyone help. Regards Paul

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  • Use C function in C++ program; "multiply-defined" error

    - by eom
    I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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  • SQL Query taking too long

    - by user345426
    I am trying to optimize the SQL query listed below. It is basically a search engine code that retrieves products based on the products name. It also checks products model number and whether or not it is enabled. This executes in about 1.6 seconds when I run it directly through the phpMyAdmin tool but takes about 3 seconds in total to load in conjunction with the PHP file it is placed in. I need to add a category search functionality and now that is crashing the MySQL server, HELP! SELECT DISTINCT p.products_id , p.products_image , p.products_price , s.specials_new_products_price, p.products_weight , p.products_unit_quantity , pd.products_name , pd.products_img_alt , pd.products_affiliate_url FROM products AS p LEFT JOIN vendors v ON v.vendors_id = p.vendors_id LEFT JOIN specials AS s ON s.products_id = p.products_id AND s.status = 1, categories AS c , products_description AS pd , products_to_categories AS p2c WHERE ( ( pd.products_name LIKE '%cleaning%' AND pd.products_name LIKE '%supplies%' ) OR ( p.products_model LIKE '%cleaning%' AND p.products_model LIKE '%supplies%' ) OR p.products_id = 'cleaning supplies' OR v.vendors_prefix = 'cleaning supplies' OR CONCAT( CAST(v.vendors_prefix AS CHAR), '-', CAST(p.products_id AS CHAR) ) = 'cleaning supplies' ) AND p.products_status = '1' AND c.categories_status = '1' AND p.products_id = pd.products_id AND p2c.products_id = pd.products_id AND p2c.categories_id = c.categories_id ORDER BY pd.products_name

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • Sort an array via x86 Assembly (embedded in C++)?? Possible??

    - by Mark V.
    I am playing around with x86 assembly for the first time and I can't figure out how to sort an array (via insertion sort).. I understand the algorithm, but assembly is confusing me as I primarily use Java & C++. Heres all I have so far int ascending_sort( char arrayOfLetters[], int arraySize ) { char temp; __asm{ push eax push ebx push ecx push edx push esi push edi //// ??? pop edi pop esi pop edx pop ecx pop ebx pop eax } } Basically nothing :( Any ideas?? Thanks in advance.

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  • Removing first two elements of a string array in C

    - by sandeep p
    How can I remove first two elements of a string array? I have a code which is something like this. char *x[10]; .............. .............. .............. char *event[20]; event[0]=strtok(x[i]," "); event[1]=strtok(NULL," "); event[2]=strtok(NULL," "); event[3]=strtok(NULL," "); event[4]=strtok(NULL," "); event[5]=strtok(NULL," "); for(i=2;i<length;i++) { strcpy(event[i-2],event[i]); } I observed that only event[0] has proper values. I printed the contents of event[][] before for loop and it displays correctly. Could you please tell me why this is wrong? and a possible solution?

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  • Class Members Over Exports

    - by VirusEcks
    When Using DLLs or Code-injecting to be Specific this is an example class only intended for explaining class test { int newint1; char newchararray[512]; void (*newfunction1)( int newarg1 ); int newfunction2( bool newarg1, char newarg2 ) { return newint1; } } mynewclass1; that covers most common elements that's included in classes now when exporting this function to another DLL or application and missed an element of those, either data member or function member, private or public what happens or changed their order ? and if each function is assigned it's value when Code-Injecting like mynewclass1.newfunction1 = (void *)(newexportedfunction); what's the happens in this case, if members of the class are pointers that are assigned after class construction and then missed one member or changed their order ?

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  • What is wrong with this c strdup code?

    - by bstullkid
    Consider this code: char *strs[] = { "string1", "string2", NULL }; char *ptr1 = NULL, *ptr2 = NULL, *tmp; short iter = 0; tmp = ptr1; while (iter < 2) { tmp = strdup(strs[iter]); tmp = ptr2; iter++; } printf("1: %s\n2: %s\n", ptr1, ptr2); I want this to output "string1\nstring2\n" however str1 and str2 remain null. What am I doing wrong?

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  • function in c language

    - by sandy101
    Hello, I am practice the function in c and come across to the program .... include int main() { float a=15.5; char ch ='C'; printit(a,ch); return 0; } printit(a,ch) { printf("%f\n%c",a,ch); } I want to know that why the above program compile and not give the error as i understood so for is ... 1) The function in c must be declared with the specific prototype (but this program does not contain the prototype ) 2)why the program give the output 'x'for the char variable 3)can the function in c are capable of accepting the value without being declared about type in parameters like what has done in the function declaration .... plz.... help

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  • How can I remove the head of a main function?

    - by Nathan McDavitt-Van Fleet
    I am trying to move some code from a seperate binary and have it inside my main program. Unfortunately I can't mimic the initialization variables for the main function. How can I create argc and argv by hand? Can someone give me some example assignments. since it looks like this: int main(int argc, char *argv[]) I figured I could assign them like this: int argc=1; char *argv[0]="Example"; But it doesn't work. Can anyone tell me how this might be done?

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