I get a run time error saying something about memory locations when I run this program.How can I make this program work using pointers?
//this program converst miles to km
#include<iostream>
#include "std_lib_facilities.h"
[Code]....
i really don't know why has a error in my code, that pass a pointer of pointer (name of a matrix with 2 dimensions). Here is the source code of a simple example where appears segmentation fault when execute (but compiles normal):
#include <stdio.h>
#define LINHAS 3
#define COLUNAS 5
float a[LINHAS][COLUNAS];
void zeros(float **p,float m, float n){
int i,j;
for(i=0;i<m;i++)
[Code]...
I have read about it in my book and also on this website but i still have things uncleared....
View 11 Replies View RelatedI'm playing around with GTK+ 2.x and currently I have a button to call a function like so:
Code:
void selectmod(GtkWidget *downloadbutton, GtkComboBox *modlist, gchar *data){
gchar *mod = gtk_combo_box_get_active_text(modlist);
printf("
%s", mod);
}
How can I pass the *mod variable to another function?
How to pass arguments from other functions to main. i want to write a program like nano well not exactly like nano editor. I have a function f_read(char* filename[]), and fopen() get filename[1] as file name and *filename[2] as "r" read mode and rest of the code will read from a file.
I want is this char filename[] to main(int argc , char argv[])
how can i do that??
I need to send same instance of object of a class in two function (Main function and thread function). The class is something like this:
//The class need to have constructor.
Class ABC {
public:
DWORD *IdG;
ABC(int number) {
IdG = new DWORD[number];
}
}obj(32);
The obj(32) is called in following two function. Function F1 is called using thread in main function.
void F1() {
obj.test;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {
obj.test1;
_beginthread(F1,0,(void*)number);
}
The code works well when the object of class ABC is created as shown above. My problem is the value that is passed in the object ('32') is to be read from the file.
If I read the file and create object separately in Main function and function 'F1' then , function 'F1' is not executed.
How to create same instance of object for Main function and function 'F1' with value passed in the object taken from the file.
I have a project for class where I have to create a structure and get user input for 3 structure variable arrays of 10. I am trying to figure out how I can use the same function to fill my different section of variables.
My Structure is an employee file of ID number, name, hours, payrate, and then gross pay. I have to create a function for each input function. I am confused on how to pass the structure variable so that I do not have to write 3 functions for each input. I would like to be able to get all the info for the first structure variable and then recall the same 5 functions for the next before moving along. I hope that I have been able to make this clear. Here is my code:
#include<iostream>
#include<iomanip>
#include<cctype>
#include<string>
#include<cstring>
using namespace std;
struct PayPeeps_CL//Payroll Structure {
[Code] .....
Code:
struct NewPlayer {
int level;
int intelligence;
int damage;
};
int CharacterInfo(NewPlayer MageWizard, int Clevel,int Cint, int Cdam)
[Code] .....
This code is for fun, and have it doing a lot of what I want it to, just not all. I want random generated to write to a txt file. I tried to use an array but that failed. I wanted to use an array because i am only passing one value. Which makes sense since the random generated function is an int.
I made the fprintf as a comment but hopefully soon it will be able to send the values to the txt file. After that I will tackle the function.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define HIGH 49
#define LOW 1
int random_generated()
[Code]...
Why do we not pass the address of the string during printf or scanf functions like we do for Integer or float variable types?
View 2 Replies View RelatedI am returning area from areaCircle(), but do not know how to print it in main. I know this program has lots of errors, two cases that I have listed.
Not sure how to properly list multiple function calls in a switch statement, and how to print one's return from main.
int main() {
char choice;
double area;
showMenu(choice);
switch (choice) // If input is C, use getRadius, areaCircle and count, then print the are
{
case 'C': void getRadius(),double areaCircle(), void count(bool display = false);
[Code]...
//program to form a header file
/* using pass by reference in pointer */
#include <iostream>
#include<math.h>
[Code].....
i need to pass myboard.board (board is in the class Cboard and it is an array of int) to a function in a class called piece however this is troubling . i need to pass it as pointer os that i could change its value here under is my code.
main.cpp Code: #include<iostream>
#include"board.h"
#include "pieces.h"
[Code].....
I'm having a problem understanding something with pointers. I was trying to pass a pointer into a function in MSVC-2013, like
char* charptr;
and then calling
myfunct(charptr);
and then inside the function i would set charptr equal to another char ptr, simply like
charptr = anothercharptr;
But this actually caused a compile failure in MSVC, saying charptr is being used without being initialized. in Code::Blocks it just gives buggy output.
I solved this issue by calling the function like
myfunct(&charptr);
and declaring the function like
myfunct(char**);
and then I had to dereference the charptr in the function when assigning it to another ptr, so
*charptr = anothercharptr;
It seems like you should be able to just pass a ptr into a function and change its address to that of another pointer? My main question is really, what is the value of a pointer? I thought the value of a pointer was just the memory address it contains. But then I had to reference it to pass it into the function.
What is the difference between the value of the char* charptr written as either charptr and &charptr?
What is the difference in pass by pointer and pass by reference? As per my understanding, there is no difference much.If a function accepts pointer, then NULL check can be performed.other than this i'm not able to see any big difference..
View 3 Replies View RelatedI have a struct which has an array inside of it:
struct someStruct{
int structArray[999];}
Now when I want to access that array, I have the following:
ptrSomeStruct->structArray[someIndex];
But now I want to pass structArray to this function by reference so that it can adjust the array as needed and I can continue to use the array back in my caller function:
void adjustArray(void *& someArray){}
How do I accomplish this?
#include <iostream>
using namespace std;
void myfunc(int* ); // what do i put in these parameters to accept a mem loc of a pointer
int main () {
int x = 5;
[Code] .....
SOLUTION:
#include <iostream>
using namespace std;
//Purpose to create a function that returns a pointer to a pointer
int** myfunc(int**);
int main () {
int x = 5;
[Code] ....
I just want to know if there is any real difference between the two below, if yes, when would i use one over the other? I would thought the "&" is pointless in below function, as far as the data is concerned.., the only things is with "&", if the pointer address value is changed in Test function, it will affect the caller's copy of data. Both function should behave the same if data is changed.
Code:
Between
void Test(QSharedPointer<Data> data)
{
}
and
void Test(QSharedPointer<Data> & data)
{
}
I don't understand how my code not run.
#include "stdafx.h"
#include<iostream>
using namespace std;
struct student{
char name[30];
char birthday[20];
char homeness[50];
float math;
[Code] ....
void extf(int a) { }
template<typename P>
struct A {
// 1
template< void (*F)(P) >
static void call(P arg) {
[Code]...
Why it is not working? What would be a proper way to pass function pointer as a template parameter?
I am trying to create a callback system for input events in my game engine.
Here is a cut down version of the EventManager.h file
#include "Controls.h"
#include "Object.h"
enum MouseEventType{PRESSED, POINTER_AT_POSITION, PRESSED_AT_POSITION };
[Code].....
This works if the function pointer being passed to the event manager is not a member function.
I have two other classes Scene and Object that could potentially use this EventManager to create callback events. Scene and Object are both pure virtual objects. How can I pass a pointer to a member function of the child classes of both Scene and Object? I am fine with just having two separate watchEvent functions for Scene and Object but how do I pass the type of the Object or the type of the Scene? The child classes are unknown as they are being created by someone using this game engine.
For example, if I want to make a player object it would be something like
class PlayerObject : public Object{...};
Now that PlayerObject type has to find its way to PlayerObject::functionToCall(). I think I need templates to do this but, since I never used them before
This is how I intend to use this
class OtherScene : public Scene{
void p_pressed(void){
//pause
}
[Code].....
I am trying use a print function to print out data in a struct. My questions are:
1. I have to use pass by reference. For the print function, I am passing the struct pointer as a reference, however, I don't want the print function to accidentally change anything. How can I make it use const to ensure that?
2. The deleteprt function doesn't look right to me. I feel like it should just be delete ptr not delete [] ptr.
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <string>
using namespace std;
struct Inventory {
[Code] .....
Why do most C examples pass a double pointer when manipulating linkedlists? Why can not we just pass a single pointer to the struct?I think using an external reference accessor for a linked list would be a more appropriate solution, yes or no?
View 1 Replies View Relatedclass A (abstract)
class B : A
class C {
void add ( A(&*?) a )
std::vector<std::unique_ptr<A>> data; //unique_ptr<A> because A is abstract and therefore vector<A> isn't possible
}
upper situation. What is the best way to pass add an object of class B to C?
with C::add(A* a){ vector.push_back( unique_ptr<A>(a) ); }
and
int main() {
C c;
c.add( new B() );
}
This works, but i don't think it's very nice, because you could delete the pointer in main. What happens then with the unique_ptr? I could probably make C::add( std::unique_ptr<A> u_p ); but maybe it can be avoided that the "user" (in main() ) has to create the unique_ptr itself.
The following code compiles and runs fine till it reaches line 16 and gets a sigsev violation which I'm not sure about as to why. I have no problem passing the object of type node** into the constructor of base and storing it into the double pointer node** copy;; but when I call the function void pass(node** temp) it crashes.
#include <iostream>
class base;
class node {
private:
node** data;
public:
[Code] .....
I made this example code to illustrate my question:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int Right(char* In, char* Out, int Position){
Out=&In[strlen(In)-Position];
[Code] ....
Well, I guess the code explains it all. I want b to be the last three characters of a using a function called "Right".
Doing exactly the same thing without the function involved works fine. I just let b point to the third last character of a.
Why does the function not work?