C++ :: When To Use Pointers
Apr 4, 2013give me a few solid examples for when one should use pointers.
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C :: Create Array Of Pointers To Pointers Which Will Point To Array Of Pointers
Feb 28, 2014I'm trying to create an array of pointers to pointers which will point to array of pointers (to strings) I tried
Code:
int i;
char *string[]={
"my name is dave",
"we like to dance together",
"sunny day",
"hello",
[code]...
the app keeps crashing , I don't know how to make the array-elements to point to another array-elements..
C++ :: Comparing Char Pointers To Integer Pointers
May 21, 2013I am a little confused while comparing char pointers to integer pointers. Here is the problem:
Consider the following statement;
char *ptr = "Hello";
char cArr[] = "Hello";
When I do cout << ptr; it prints Hello, same is the case with the statement
cout << cArr;
As ptr and cArr are pointers, they should print addresses rather than contents, but if I have an interger array i.e.
int iArr[] = {1, 2, 3};
If I cout << iArr; it displays the expected result(i.e. prints address) but pointers to character array while outputting doesn't show the address but shows the contents, Why??
C++ :: Dynamic Creation Of Arrays Of Pointers To Arrays Of Pointers
Apr 15, 2013I'm trying to write a function that takes a 32bit address and a data to store at this address.
I'm wanting to take the 32 bit memory address eg 0x12345678 and split it
into 4 x 2 bytes
12, 34, 56, 78
then each of the 4 entries is at most a 256 entry array.eg
FF, FF, FF, FF
So in this example, 0x12 points to 0x34 in the second array, which points to 0x56 in the third array, which finally points to 0x78 in the last array. This last array holds the actual data.
After successfully doing 0x12345678, say I might get a read for 0x1234AABB. So, the first and second pointers already exist, but I then have to create and write to dynamically created arrays.
The arrays need to have all entries set to NULL so that i know whether to follow the pointers to overwrite a previously entered value or create new arrays and pointers.
It all looks good and simple in the pseudo code I've written up but I'm having trouble coding it. I'm currently trying to deal with the first entry case, ie all array elements are NULL, but I'm getting confused with the pointers and creation of new arrays.
void cpu::store(unsigned int mem_add,unsigned int mem_val) {
int first = (mem_address&4278190080)>>24;
int second = (mem_address&16711680)>>16;
int third = (mem_address&65280)>>8;
int fourth= (mem_address&255);
[Code] .....
A1 has been declared as
int* A1[256] ;
C :: Gcc Compiler And Pointers
Mar 3, 2013The first sample program that I am reading on the book has the following code:
Code:
* Demonstrates basic pointer use. */
#include <stdio.h>
/* Declare and initialize an int variable */
int var = 1;
}
[code]....
Is this a compiler error or is there a proper syntax for pointers using the gcc compiler?
C++ :: Use Different Pointers For Arrays?
Dec 24, 2013So when if you want to change the values themselves for example in an array (just for example) this is valid;
void test(int* test)
{
test[0] += 10;
}
int bob[] {1, 3, 5};
If you did that bob[0] would not equal 11. All well and good right?
Now if you do this?
int sally = 33;
test(sallay);
This wouldn't work at all you actually have to use
void test(int& test)
{
test += 10;
}
how the memory addresses etc. are working here? I don't understand why you need to use & the reference operator if it's not an array? Why wouldn't that still work?
C++ :: Payroll Net Pay With Pointers
May 15, 2014Alright, after what seems like forever I'm on the last stage of modifying my Payroll Program. This time I have to sort using pointers and I only have to sort the Net Pay category.
Using one of my earlier programs I've removed content from it until it's in a state where it runs but contains no sorting functions.
So now I've to a working program that lacks any kind of sorting and looks like this.
#include <iostream>
#include <fstream>//file input output stream
#include <iomanip>
#include <string>
using namespace std;
//function prototypes
int readalldata(long int id[], string fname[], string lname[], int hoursworked[], float hourlyrate[], int n);
[Code] .....
My hints for how to add pointers to the program are...
int *np,tmp;
for (i=0,i<n; i++) np=&netpay[i]; //associating the netpay to np;
temp=np[i];//storing the pointer to a temp
I've been fooling around trying to sort the Net Pay by pointers using these hints for a bit now and I'm still not getting it.
C++ :: Set Pointers To Default Value For Both 32 Bit And 64 Bit
Sep 6, 2013I have a problem. I want to set pointers to a default value for both 32 bit and 64 bit compiles. The 32-bit version works as:
enum constants { UNDEFINED = 0xDeadBeef }
if ((unsigned long)ptr == UNDEFINED)
but I can't seem to extend this to 64-bits. I've tried
#if __SIZEOF_POINTER__ == 4
enum constants { UNDEFDATA = 0xDeadBeef };
}; // enum constants
#elif __SIZEOF_POINTER__ == 8
enum constants { UNDEFDATA = 0xDeadBeefDeadBeef };
#endif
with:
if (ptr == UNDEFINED)
but get a message saying the '==' is undefined (I understand this)
Is there any way to setup so that I can change the size of my constants so that the comparisons will always work correctly? I've tried a 'typedef' but the compiler complains at
'typedef unsigned long long ADDR' // won't accept, and
static const SlipCellBase * const TEMPORARY = (SlipCellBase&)0xFFFFFFFFFFFFFFFF; // illegal conversion
enum doesn't work (because it's an int?)
C/C++ :: Pointers And Structs
Dec 14, 2014What the second print statement prints
main() {
struct s1{
char *str;
int i;
struct s1 *ptr;
[Code] .....
I executed the code and the output was some number(for second printf) but it should print a string.
C++ :: Use The Void Pointers?
Nov 25, 2013how can i use the void pointers? i understand that can recive an adress variable(&). but can recive a value?
Code:
int a=5;
void *d;
b=&a;
b=100;//???
why i can't do these?
Visual C++ :: Value Of Pointers
Feb 5, 2013I'm trying to figure out the value of pointers after the following code snippet
Code:
int s[8] ;
int *iptr1, *iptr2 ;
int **iptr3 ;
for (int i = 0 ; i < 8 ; i++)
s[i] = 7 - i ;
[Code] ....
I need to find what the value of iptr1, iptr2, and iptr3 are after the code is executed.
C++ :: What Are Function Pointers
May 21, 2012What are Function pointers , what are the benefits of using it?
View 4 Replies View RelatedC++ :: Using Pointers To Change Some Value On The Fly?
May 13, 2015I've got an interface that provides the methods that are to be implemented
Code:
class A {
virtual void A() = 0;
}
class B : public A {
std::string operator<<(const std::string& lhs);
[Code] ....
I don't know why the << operator in B is never called..
C++ :: Matrix Multiplication Using Pointers
Feb 15, 2014Code:
#include<stdio.h>
#include<conio.h>
void main()
[Code] .....
This program on running returns an error of "ILLEGAL USE OF POINTER".
C :: How To Use Character Pointers Instead Of Arrays
Apr 14, 2013Here is my program to look up words. How do I use character pointers instead of using arrays?
Code:
#include <stdio.h>
struct entry
{
[Code].....
C :: Passing Pointers Into Function?
Dec 3, 2013I want to scan numbers in from within a function, but have access to them in main, so I tried using pointers to do so:
Code:
// Path Of Exile socket colours simulation
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
[Code].....
C :: Dynamic Arrays And Pointers
Feb 11, 2013I am having troubles with dynamic arrays and pointers. All the errors are of that kind. I think when I am assigning malloc to an array we assign to its address.
Code:
/*Create an array of genes of the large matrix*/
gene_t gene,gene1,gene2;
gene=malloc(INITIAL*sizeof(gene2)); Code:
while(...) {
if (gene_num==current_size){
[Code] .....
C :: Memcpy Between Void Pointers
Feb 13, 2014I am trying to add data to a queue with the following simplified code:
Code:
typedef struct Queue {
void * data;
int head;
int tail;
int elementSize;
My question is, how do I move the queue->data pointer to the correct memory location in order to copy given data to head? The code above inside memcpy gives med the error: "expression must be a pointer to a complete object type".
Do I need an extra pointer to be able to navigate between the queue's head and tail, and keep queue->data as a reference to the first byte of the allocated memory, or is it possible with only queue->data?
Edit. Just noticed I have mixed up head and tail. The enqueued data should probably go to the Queue's tail and not the head. However, the problem is still the same.
C :: Setting Values To Pointers
Apr 5, 2014This function below takes a pointer as an argument. What I expect to happen is, since expr++ has higher precedence than *expr, that is, the primary expression operators have higher precedence than the unary operators, pointer arithmetic should occur where we increment to the second address pointed to by dbuf, and then we should dereference the value at that address. Given that logiv, when i print dbuf[3] it should print the value pointed to at the 4th address in dbuf. However, the value it returns is 0x0 not 0x3. Why doesn't it dereference the value 0x3?
Code: void dfill(unsigned char *dbuf)
{
dbuf = (unsigned char*)malloc(4);
memset(dbuf, 0, 4);
*dbuf = 0x0;
*dbuf++ = 0x1;
*dbuf++ = 0x2;
*dbuf++ = 0x3;
printf("dbuf val: 0x%x
", dbuf[3]);
}
C :: Size Of Function And Pointers
Apr 6, 2014I have this simple program:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static unsigned char cmd[]={
0x01,0x80,0x00,0x00,0x00
[Code] .....
All is right except the size. Why does it give 80x1 as size instead of the digit 5?
C :: Matrix Multiplication Using Pointers
Feb 17, 2014Code:
#include<stdio.h> Code: #include<conio.h>
void main() {
int *a[2][2],*b[2][2],*c[2][2],i,j,k;
Printf("
ENTER a MATRIX ELEMENTS
[Code] .....
C :: For Loop Controller Using Pointers?
Jan 3, 2015I'm familiar with the concept of int in the for loop. However, I've seen a case where the condition for the for loop is a pointer. How is the pointer used or interpreted in the for loop condition in C or C++.
As an example:
Code:
void printer(char *fmt, ...) {
va_list args;
char *p, *sval;
int ival;
double dval;
va_start(args, fmt);
for(p = fmt; *p; p++) {
if(*p != '%') {
putchar(*p);
continue;
[Code]....
C :: Array Of Pointers To A Struct?
May 10, 2013I am working on an assignment identical to another post from a couple years ago, for reference here is the thread:
array of pointers to structures sorting addresses by zip code
They way it is written on that thread is almost identical to the way the teacher implied to have it done (only wrote part of the input block). But I am having an error:
When it gets to the output section it outputs then next name along with the zip code... I tried strncpy and strxfrm but both cause more problems than they did work.
The last part of the project is to have the output put out in order of least zip code to most zip code (00000<99999), so this is causing me a real problem and I do not see what exactly is making this happen.
Here is my code (we dont HAVE to use gets but professor suggested using it for this assignment, next lab is to rewrite this using files and fgets rather than I/O redirection):
header.h Code: #ifndef lab_6b_7b_Header_h
#define lab_6b_7b_Header_h
//header file intiating other headers
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct{
[code]....
I have not started the sorting code because I cannot get past this, but once I have proper zip codes I am sure I can make a sort function no problem.
I am using xcode with some breaks to read variables as various points and do not notice anything wrong until it makes it to the output functions, although this page briefly pops up between input and output functions when the breaks are up:
C :: Use Pointers Instead Of Global Variables?
Oct 15, 2014I have made an application and I have basically solved everything. But the only problem is that I am using global variables because it felt like the smoothest, so my program is built on it.
But now I've read around and I understand that you should not use these(?). Do you think pointers is the best think to use instead?I have previously declared my board array and some variables as global and I want them in alot of functions.I have read and understand the procedure for the use of pointers so I can use my int's in the other functions by doing like this? Code: #include <stdio.h>
int justprint();
int main()
{
int Row = 2;
int Column = 2;
int *pRow = &Row;
int *pColumn = &Column;
[code]...
But how do I do it with an array like this one? If I declare it in the main function, and then want to use it in other functions.Or are there better, easier solutions?
Code: char game[3][3]={{0,0}};
C :: Arrays And Pointers In A Loop
Jun 27, 2013Set an Array (a[10]) and a Pointer to that array (*pa) and code a loop (for( ; ; loop) that will advance that pointer (*pa) and will set a new content into it with each loop. that means that in the end of the day, my program will automatically set content to each cell of the array by promoting the pointer by 1 and add the sum to that pointer.
When I run the program it prints the address of the cells instead the value of it.
Code:
#include <stdio.h>
void main() {
float a[11], *pa; // Array and ptr set.
int i; // counter for the loop.
pa = a;
for (i=0 ; i<=10 ; i++) // the loop itself.
[Code] .....
C :: Trying To Flip A String Using Pointers
Sep 12, 2013Having some trouble with basic stuff while learning C. My purpose was to flip the pointing order, so it would point to the string from the end to the start. didn't work so well using **str as well.
Code:
#include <stdio.h>
#include <conio.h>
char str_inve(char *ptr);
[Code] .....