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  • (gcc) Multi-Dim Array or Double Pointer for Warning-free Compile

    - by paul simmons
    Hi, I have a function, which is called sometimes with regular, sometimes dynamic arrays. If I define the function as function_name(int[10][10] a) and send int** as a parameter, I get a warning. Opposite, if I declare function_name(int** a) and send int[][] as a parameter (after casting) I cannot access to array elements inside function. What is the correctest way?

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  • c++ protected pointer member to the same class and access privileges

    - by aajmakin
    Hi, Example code is included at the bottom of the message. I'm puzzled about the protected access specifier in a class. I have define a class node which has a protected string member name string name; and a vector of node pointers vector args; Before I thought that a member function of node could not do args[0]-name but a program that does just this does compile and run. However, now I would like to inherit this class and access the name field in one of the args array pointers from this derived class args[0]-name but this does not compile. When I compile the example code below with the commented sections uncommented, the compiler reports: Compiler output: g++ test.cc -o test test.cc: In member function 'void foo::newnode::print_args2()': test.cc:22: error: 'std::string foo::node::name' is protected test.cc:61: error: within this context Compilation exited abnormally with code 1 at Thu Jun 17 12:40:12 Questions: Why can I access the name field of the node pointers in args in class node, because this is what I would excpect from a similarly defined private field in Java. How can I access those fields from the derived class. Example code: #include <iostream> #include <vector> using namespace std; namespace foo { class node; typedef std::vector<node*> nodes; class node { public: node (string _name); void print_args (); void add_node (node* a); protected: nodes args; string name; }; } foo::node::node (string _name) : args(0) { name = _name; } void foo::node::add_node (node* a) { args.push_back(a); } void foo::node::print_args () { for (int i = 0; i < args.size(); i++) { cout << "node " << i << ": " << args[i]->name << endl; } } // namespace foo // { // class newnode : public node // { // public: // newnode (string _name) : node(_name) {} // void print_args2 (); // protected: // }; // } // void foo::newnode::print_args2 () // { // for (int i = 0; i < args.size(); i++) // { // cout << "node " << i << ": " << args[i]->name << endl; // } // } int main (int argc, char** argv) { foo::node a ("a"); foo::node b ("b"); foo::node c ("c"); a.add_node (&b); a.add_node (&c); a.print_args (); // foo::newnode newa ("newa"); // foo::newnode newb ("newb"); // foo::newnode newc ("newc"); // newa.add_node (&newb); // newa.add_node (&newc); // newa.print_args2 (); return 0; }

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  • Jquery multiple events to trigger the same function

    - by dweebsonduty
    Is there a way to have keyup, keypress, blur, and change events call the same function in one line or do I have to do them separately? The problem I have is that I need to validate some data with a db lookup and would like to make sure that there is no way that the validation is missed weather it is typed or pasted into the box.

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  • Typcast a null pointer to char*

    - by user326253
    Suppose I have a char* elem that is supposed to hold a char*, s.t. elem[0] = char*, elem[1...m]= more chars. Is there a way I can put a null ptr within char* elem? When I try to set elem = NULL, it gives me a type error because NULL is an int. Any help would be greatly appreciated!

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  • Cryptic C++ "thing" (function pointer)

    - by m00st
    What is this syntax for in C++? Can someone point me to the technical term so I can see if I find anything in my text? At first I thought it was a prototype but then the = and (*fn) threw me off... Here is my example: void (*fn) (int&,int&) = x;

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  • C++ print value of a pointer

    - by user69514
    I have an array of double pointers, but every time I try do print one of the values the address gets printed. How do I print the actual value? cout << arr[i] ? cout << &arr[i] ? they both print the address Does anyone know?

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  • Pointer and malloc issue

    - by Andy
    I am fairly new to C and am getting stuck with arrays and pointers when they refer to strings. I can ask for input of 2 numbers (ints) and then return the one I want (first number or second number) without any issues. But when I request names and try to return them, the program crashes after I enter the first name and not sure why. In theory I am looking to reserve memory for the first name, and then expand it to include a second name. Can anyone explain why this breaks? Thanks! #include <stdio.h> #include <stdlib.h> void main () { int NumItems = 0; NumItems += 1; char* NameList = malloc(sizeof(char[10])*NumItems); printf("Please enter name #1: \n"); scanf("%9s", NameList[0]); fpurge(stdin); NumItems += 1; NameList = realloc(NameList,sizeof(char[10])*NumItems); printf("Please enter name #2: \n"); scanf("%9s", NameList[1]); fpurge(stdin); printf("The first name is: %s",NameList[0]); printf("The second name is: %s",NameList[1]); return 0; }

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  • Changing pointer of self

    - by rob5408
    I have an object that I alloc/init like normal just to get a instance. Later in my application I want to load state from disk for that object. I figure I could unarchive my class (which conforms to NSCoding) and just swap where my instance points to. To this end I use this code... NSString* pathForDataFile = [self pathForDataFile]; if([[NSFileManager defaultManager] fileExistsAtPath:pathForDataFile] == YES) { NSLog(@"Save file exists"); NSData *data = [[NSMutableData alloc] initWithContentsOfFile:pathForDataFile]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; [data release]; Person *tempPerson = [unarchiver decodeObjectForKey:@"Person"]; [unarchiver finishDecoding]; [unarchiver release]; if (tempPerson) { [self release]; self = [tempPerson retain]; } } Now when I sprinkled some NSLogs throughout my application I noticed self.person: <Person: 0x3d01a10> (After I create the object with alloc/init) self: <Person: 0x3d01a10> (At the start of this method) tempPerson: <Person: 0x3b1b880> (When I create the tempPerson) self: <Person: 0x3b1b880> (after i point self to the location of the tempPerson) self.person: <Person: 0x3d01a10> (After the method back in the main program) What am I missing?

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  • Magento order status change events

    - by Christian
    Hi people, I want to change via web service a remote inventory, I know that via Event Observer Method can triger my code, but I don't know which event is useful to complete my task, like on_order_complete, is there an updated list of events or more documentation?

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  • "assignment makes integer from pointer without a cast " warning in c

    - by mekasperasky
    #include<stdio.h> /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i=0,j; char a,b[20],c[30]; FILE *fp1,*fp2; c[0]='"if"; c[1]="then"; c[2]="else"; c[3]="switch"; c[4]="printf"; c[5]="scanf"; c[6]="NULL"; c[7]="int"; c[8]="char"; c[9]="float"; c[10]="long"; c[11]="double"; c[12]="char"; c[13]="const"; c[14]="continue"; c[15]="break"; c[16]="for"; c[17]="size of"; c[18]="register"; c[19]="short"; c[20]="auto"; c[21]="while"; c[22]="do"; c[23]="case"; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer fp2=fopen("lext.txt","w"); //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; while(!feof(fp1)) { a=fgetc(fp1); if(a!=' ') { b[i]=a; } else { for (j=0;j<23;j++) { if(c[j]==b) { fprintf(fp2, "%.20s\n", c[j]); continue ; } b[i]='\0'; fprintf(fp2, "%.20s\n", b); i=0; continue; } //else if //{ i=i+1; /*Switch(a) { case EOF :return eof; case '+':sym=sym+1; case '-':sym=sym+1; case '*':sym=sym+1; case '/':sym=sym+1; case '%':sym=sym+1; case ' */ } fclose(fp1); fclose(fp2); return 0; } This is my c code for lexical analysis .. its giving warnings and also not writing anything into the lext file ..

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  • Lots of pointer casts in QGraphicsView framework and performance

    - by kleimola
    Since most of the convenience functions of QGraphicsScene and QGraphicsItem (such as items(), collidingItems(), childItems() etc.) return a QList you're forced to do lots of qgraphicsitem_cast or static_cast and QGraphicsItem::Type() checks to get hold of the actual items when you have lots of different type of items in the scene. I thought doing lots of subclass casts were not a desirable coding style, but I guess in this case there are no other viable way, or is there? QList<QGraphicsItem *> itemsHit = someItem->collidingItems(Qt::IntersectsItemShape); foreach (QGraphicsItem *item, itemsHit) { if (item->type() == QGraphicsEllipseItem::type()) { QGraphicsEllipseItem *ellipse = qgraphicsitem_cast<QGraphicsEllipseItem *>(item); // do something } else if (item->type() == MyItemSubclass::type()) { MyItemSubClass *myItem = qgraphicsitem_cast<MyItemSubClass *>(item); // do something } // etc } The above qgraphicsitem_cast could be replaced by static_cast since correct type is already verified. When doing lots of these all the time (very dynamic scene), will the numerous casting affect performance beyond the normal if-else evaluation?

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  • dynimically using pointer

    - by gcc
    Input: 3 1 2 n 4 5 d 1 21 30 x Output: 2: 4 5 21 30 Input: 3 j 3 34 6 22 10 51 n 1 2 j 1 3 4 5 n 6 7 x Output: 1: 1 2 3 4 5 2: 6 7 3: 34 6 22 10 51 'j': (Jump to array# command) 'd': (Delete array# command) 'n': (Next array command) 'x': (Exit command) #: (Integer number) int num_arrays; /* maximum number of arrays */ int **arrays; /* array of array pointers */ int *l_arrays; /* actual lengths of arrays */ int *c_arrays; /* actual capacities of arrays */ how can we write that code

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  • Java: Using GSon incorrectly? (null pointer exception)

    - by Rosarch
    I'm trying to get the hits of a google search from a string of the query. public class Utils { public static int googleHits(String query) throws IOException { String googleAjax = "http://ajax.googleapis.com/ajax/services/search/web?v=1.0&q="; String json = stringOfUrl(googleAjax + query); JsonObject hits = new Gson().fromJson(json, JsonObject.class); return hits.get("estimatedResultCount").getAsInt(); } public static String stringOfUrl(String addr) throws IOException { ByteArrayOutputStream output = new ByteArrayOutputStream(); URL url = new URL(addr); IOUtils.copy(url.openStream(), output); return output.toString(); } public static void main(String[] args) throws URISyntaxException, IOException { System.out.println(googleHits("odp")); } } The following exception is thrown: Exception in thread "main" java.lang.NullPointerException at odp.compling.Utils.googleHits(Utils.java:48) at odp.compling.Utils.main(Utils.java:59) What am I doing incorrectly? Should I be defining an entire object for the Json return? That seems excessive, given that all I want to do is get one value. For reference: the returned JSON structure.

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  • c# Wrapper to native c++ code, wrapping a parameter which is a pointer to an array

    - by mb300dturbo
    Hi, I have the following simple DLL in c++ un-managed code; extern "C" __declspec(dllexport) void ArrayMultiplier(float (*pointerArray)[3], int scalar, int length); void ArrayMultiplier(float (*pointerArray)[3], int scalar, int length) { for (int i = 0 ; i < length ; length++) { for (int j = 0; j < 3; j++) { pointerArray[i][j] = pointerArray[i][j] * scalar; } } } I have tried writing the following wrapper function for the above in c#: [DllImport("sample.dll")] public static extern void ArrayMultiplier(ref float elements, int scalar, int length); where elements is a 2 dimentional 3x3 array: public float[][] elements = { new float[] {2,5,3}, new float [] {4,8,6}, new float [] {5,28,3} }; The code given above compiles, but the program crashes when the wrapper function is called: Wrapper.ArrayMultiplier(ref elements, scalar, length); Please help me here, and tell me whats wrong with the code above, or how a wrapper can be written for a simple c++ function: void SimpleFunction(float (*pointerToArray)[3]); Thank you all in advance

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  • Cast A primitive type pointer to A structure pointer - Alignment and Padding?

    - by Seçkin Savasçi
    Just 20 minutes age when I answered a question, I come up with an interesting scenario that I'm not sure of the behavior: Let me have an integer array of size n, pointed by intPtr; int* intPtr; and let me also have a struct like this: typedef struct { int val1; int val2; //and less or more integer declarations goes on like this(not any other type) }intStruct; My question is if I do a cast intStruct* structPtr = (intStruct*) intPtr; Am I sure to get every element correctly if I traverse the elements of the struct? Is there any possibility of miss-alignment(possible because of padding) in any architecture/compiler?

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  • Pointer mysteriously moves

    - by Armen Ablak
    Hi, I have this code for Node rotation and in a line which is marked something happens and I don't really know what and why :). //Test case 30 \ 16 / 29 RotationRight(node->mParent); //call template<class T> void SplayTree<T>::RotationRight(SplayNode<T> *&node) const { SplayNode<T> *left = node->mLeft; SplayNode<T> *parent = node->mParent; node->mLeft = left->mRight; if(left->HasRight()) left->mRight->mParent = node; left->mRight = node; //node in this line points to 0x00445198 {30} left->mParent = node->mParent; //and in this line it points to 0x00444fb8 {16} (node, not node->mParent) node->mParent = left; node = left; } Well, left-mParent points to node also, so I basically do node = node-mParent. The problem is I can't find a work around - how to unpin in from node and change it's pointing address without changing it's.

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  • Dereferencing possible null pointer in java

    - by Nealio
    I am just starting to get into graphics and when I am trying to get the graphics, I get the error"Exception in thread "Thread-2" java.lang.NullPointerException" and I have no clue on what is going on! Any help is greatly appreciated. //The display class for the game //Crated: 10-30-2013 //Last Modified: 10-30-2013 package gamedev; import gamedev.Graphics.Render; import gamedev.Graphics.Screen; import java.awt.Canvas; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import java.awt.image.DataBufferInt; import javax.swing.JFrame; private void tick() { } private void render() { System.out.println("display.render"); BufferStrategy bs = this.getBufferStrategy(); if (bs == null) { createBufferStrategy(3); } for (int i = 0; i < GAMEWIDTH * GAMEHEIGHT; i++) { pixels[i] = screen.PIXELS[i]; } screen.Render(); //The line of code that is the problem Graphics g = bs.getDrawGraphics(); //end problematic code g.drawImage(img, 0, 0, GAMEWIDTH, GAMEHEIGHT, null); g.dispose(); bs.show(); }

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  • How to use pointers and pointer aritmetic

    - by booby
    : error C2064: term does not evaluate to a function taking 1 arguments : error C2227: left of '-name' must point to class/struct/union/generic type how do i fix this so this error doesn't happen for(int index = 0; index < (numStudents); index++) { if (student(index + 1)->score >= 90 ) student(index + 1)->grade = 'A'; else if (student(index + 1)->score >= 80 ) student(index + 1)->grade = 'B'; else if (student(index + 1)->score >= 70 ) student(index + 1)->grade = 'C'; else if (student(index + 1)->score >= 60 ) student(index + 1)->grade = 'D'; else student(index + 1)->grade = 'F'; }

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  • Indexing with pointer C/C++

    - by Leavenotrace
    Hey I'm trying to write a program to carry out newtons method and find the roots of the equation exp(-x)-(x^2)+3. It works in so far as finding the root, but I also want it to print out the root after each iteration but I can't get it to work, Could anyone point out my mistake I think its something to do with my indexing? Thanks a million :) #include <stdio.h> #include <math.h> #include <malloc.h> //Define Functions: double evalf(double x) { double answer=exp(-x)-(x*x)+3; return(answer); } double evalfprime(double x) { double answer=-exp(-x)-2*x; return(answer); } double *newton(double initialrt,double accuracy,double *data) { double root[102]; data=root; int maxit = 0; root[0] = initialrt; for (int i=1;i<102;i++) { *(data+i)=*(data+i-1)-evalf(*(data+i-1))/evalfprime(*(data+i-1)); if(fabs(*(data+i)-*(data+i-1))<accuracy) { maxit=i; break; } maxit=i; } if((maxit+1==102)&&(fabs(*(data+maxit)-*(data+maxit-1))>accuracy)) { printf("\nMax iteration reached, method terminated"); } else { printf("\nMethod successful"); printf("\nNumber of iterations: %d\nRoot Estimate: %lf\n",maxit+1,*(data+maxit)); } return(data); } int main() { double root,accuracy; double *data=(double*)malloc(sizeof(double)*102); printf("NEWTONS METHOD PROGRAMME:\nEquation: f(x)=exp(-x)-x^2+3=0\nMax No iterations=100\n\nEnter initial root estimate\n>> "); scanf("%lf",&root); _flushall(); printf("\nEnter accuracy required:\n>>"); scanf("%lf",&accuracy); *data= *newton(root,accuracy,data); printf("Iteration Root Error\n "); printf("%d %lf \n", 0,*(data)); for(int i=1;i<102;i++) { printf("%d %5.5lf %5.5lf\n", i,*(data+i),*(data+i)-*(data+i-1)); if(*(data+i*sizeof(double))-*(data+i*sizeof(double)-1)==0) { break; } } getchar(); getchar(); free(data); return(0); }

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  • What does this pointer-heavy C code do?

    - by justRadojko
    Could someone explain to me what should two following lines do: s.httpheaderline[s.httpheaderlineptr] = *(char *)uip_appdata; ++((char *)uip_appdata); This is taken from uIP code for microcontrollers. s - structure httpheaderline - http packet presented as a string httpheadrlineptr - integer value uip_appdata - received ethernet packet (string) If some more info is needed please let me know. BTW. Eclipse is reporting an error on the second line with message Invalid lvalue in increment so i'm trying to figure out how to solve this.

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