I have the following situation:
Code:
void myFun(float *pfMyPtr) {
float Val[] = {0.234, 0,432, 0.322, 0762, 0.984};
pfMyPtr = Val;
}
int main() {
float *pfPtr;
pfPtr = (float*) calloc (5,sizeof(float));
myFun(pfPtr);
}
I would like pfPtr to contain the values of array Val. What am I missing here?
I declared a pointer in main with value 0, so I want to change its value so that it points to other variable from a function, I guess the function creates a copy of my pointer that's why whatever I do within function doesn't change the real direction of the pointer in main. I've been trying something like this:
#include <stdio.h>
void redirectionate(char *str, char *ptrCopy);
int main()
{
[Code]....
Trying to get code to look like
Row 1: ^^^
Row 2: ^^^
Row 3: ^^^
const int siz = 3;
for (int t=0; t<siz;t++) {
cout << "Row" << t+1 << ":";
cout << endl;
[Code] ....
Also was wondering if i wanted to separately ask the user to choose a location to add a char who would i do that ?
( im thinking * cin << arry[][]; ? not sure but ask for them separately
array []1
array []2
= array [][]
Lets say i have an array with the values 1, 5, 9, and 3. is there anyway to make this so i can have an int with the value 1593 based on those numbers in the array?
View 8 Replies View RelatedI'm trying to set all the elements of my array to 0 but nothing seems to be working.
.h
#ifndef ServerGroup_h
#define ServerGroup_h
class ServerGroup {
public:
ServerGroup(const int&);
[Code] .....
I want to set each element of the array in servers to 0 based on what is passed into size by numArray.
How do I set all of these string and double value(s) to 0?
Code:
#define MAXcharacters 12
#define MAXaccounts 100
struct Records {
char userid[MAXcharacters + 1];
char password[MAXcharacters + 1];
double balance;
};
[code]...
Okay so I've declared an array like this.
Foo *Blocks[100][100][10000] = {0};
And as far as my understanding goes This creates an array with every member set to NULL.
And then later on in my code some of these get given values using:
Blocks[a][b][c] = new Foo;
And then when I want to unload I would think that I could just go
Blocks = {0};
But obviously this doesn't work.
So I was wondering if there was a way of doing This, with out creating a loop and changing every one to NULL manually.
I am attempting to change a character in a character array.In the code below, there are three attempts to do this. Only the first one will succeed. The last two both segfaults. If I understand correctly, str_one is declared in the heap, and could therefore be manipulated; and in contrast, str_two is declared in the stack and is therefore immutable, thus the segfault, when update it is attempted. However, I understand that using malloc, one is able to assign a pointer and allocate space in heap memory. Thus, I should be able to manipulate the assigned variable str_three. Doing so, however, results in a segfault.
Code:
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char const* argv[])
{
char str_one[4092] = "This is string number one";
char * str_two = "This is string number two";
[Code]...
i have been fiddling with pointers but I don't understand how the proper syntax is written when I want to acces an element of an array through a pointer to a pointer...The code is all mostly just random bs for learning purposes. I marked the problem "// THIS LINE"
Code:
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#define MAX_DATA 100
int find_average(char *iden, ...) {
[Code]...
This is a sample program that declares a Matrix as a structure with an array as a pointer to a pointer. The following program is supposed to store a matrix in the structure "_Matrix" and later print the matrix just entered but it fails giving me a "segmentation fault". The sample code is given below
Code:
#include <stdio.h>
#include <stdlib.h>
struct _Matrix {
int row_size;
int col_size;
int **mat;
[Code] ......
I have the following code :
Code:
#ifndef TDYNAMICARRAY_H
#define TDYNAMICARRAY_H
namespace Massive {
template<class T>
T **AllocateDynamic2DArray(int nRows,int nCols)
[Code] .....
I wish to know how to traverse or loop through a dynamic 2D array using pointer to pointer as returned by the code above. Like I would in a static T[20][20] 2D array.
I want to set limit on cin for example
int i;
cout<<"Please enter 4 digits id: ";
cin>>i
If user enter more then 4 digits it must give an error
In my refference book I have got a example with a part saying to access the a[4][0] element of the array (named a) with pointer this can be written:
*((int*)a+4)
I wonder if the cast is really required. The book says it is required so that the pointer arithmetic can be done properly. However I am not sure about it. When I work with pointers defined by myself I don't use casts similar to this one. Is there a difference between a self defined pointer and array name?
I have written this code, and at first glance it does what I want, however I am worried that
a) I am overwriting the array that is apssed from chord.getPattern()
b) Im getting a memory leak that I want to get rid of, and
c) is there generally a /what is the neater way to do it:
Code:
uint8_t* ChordBuilder::invert(uint8_t count, Chord chord) {
temp = chord.getPattern();
chord.invert(true);
//TODO count is how many times to invert. Moves root aswell however
for (uint8_t i = 0; i < count; i++){
[Code] ....
temp is a member variable of ChordBuilder - and is expressed as: Code: uint8_t* temp; I dont want the pattern that chord stores, and passes with getPattern() to change - I fear it is at the moment?
I would rather not use the "new" but I cant think how to get rid of it, however Im not sure where I would need to put the "delete"?
What is the correct method of declaring pointer to multidimensional array
Code:
int array[3][4];
int *p = array;
The above code works but it shows warning. Is it an invalid way of using the pointer? the array is an address then why am i getting warning?
int * ptr = new int[5];
p += 2; //p now stores address of 3rd element in array
delete [] p;
what will be deleted??? all 5 elements or just 3rd, 4th and 5th elements of array(in result making a memory leak)
Why would you ever assign a pointer to an existing array?Take this link for example. URL....I understand that pointers use dynamic memory allocation so they are much more flexible then a built in array, but if you already have an existing array, don't you already have static memory allocation for that array? Why bother assigning a pointer? Regardless of the pointer, doesn't the program still allocate static memory to the array anyway?
View 3 Replies View RelatedI'm given a .cpp file (for homework), this file populates an array from a file, that contains only numbers, using the standard method of populating an array but I'm supposed to modify it so that the array gets populated using a pointer, pretty simple right? Not so for me, I think I'm still confused on the concept of pointers. Here's what I have so far...
int main()
{
const int MAX_SIZE = 10;
[Code].....
I like to use a Pointer to char array. And then I would like to do a Pointer Arithmetic by incrementing the Pointer. Finally I would like to see the Addresses of the Pointer to each of the char Array Elements. I had created a program below, but I am not getting any Addresses from my Pointer.
#include <iostream>
using namespace std;
int main () {
int ArraySize;
char ch[]= "This is a Char Pointer";
char* iPtr = ch;
[Code] ....
I'm just trying to get a handle on the uses of pointers here. Though clearly from my errors I'm missing a key concept. Here is my code: (You can assume that the array, "array_size" has values in it, I did this part in another function)
int main() {
bool **ptr_array;
int num;
int *array_size;
cin>>num;
[Code] ....
Once the program reaches the word[num] = false; some unhandled exceptions pop up.
I simplified my code a bit from my actual program and mixed up the loops, now the code should be in its correct form.
How would I go about having a pointer to an array element specificity a character in a c-string.Every thing I try will not even build.An array is already a pointer to the first location of the array right?
char *pHead;
char *pTail;
pHead = sentence[0]; <=== This wont build
pHead = &sentence[0];
pHead = sentence[0]*;
*pHead = sentence[0]; <===== this builds but is not storing anything
int sum(int (*ar2)[4], int size);
// I dont know what the ar2 is going on
int main(){
int data[3][4] = {{1,2,3,4},{5,6,7,8},{9,10,11,12}};
int total = sum(data, 3)
return 0;
}
I was struggling the last 2 days with this C script supposing to open a list of strings (input as fopen(argv[1])and allowing to access to any element of the list. I created an array *gcm[10000] and a pointer *(*gcm_ptr[10000] = &gcm. However, when I try to list whatever n[i], it always gives me the last entry.
View 4 Replies View RelatedThis 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]);
}
I am trying to create the lparam for the WM_KEYDOWN message. I know this is the C programming forum, but my code is standard enough to apply here. According to Microsoft, the lparam must be formatted like this : lParam The repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown following. Bits Meaning 0-15 The repeat count for the current message. The value is the number of times the keystroke is autorepeated as a result of the user holding down the key. If the keystroke is held long enough, multiple messages are sent.
However, the repeat count is not cumulative. 16-23 The scan code. The value depends on the OEM. 24 Indicates whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0. 25-28 Reserved; do not use. 29 The context code. The value is always 0 for a WM_KEYDOWN message. 30 The previous key state.
The value is 1 if the key is down before the message is sent, or it is zero if the key is up. 31 The transition state. The value is always 0 for a WM_KEYDOWN message. ( WM_KEYDOWN message (Windows) )^ I'm troubled by setting it into the 32-bit value, and I get confused about what exactly happens when the logical or and the bitshift operators are used. I tried to use them below in my code by looking at Stack Overflow for setting a bit. I also don't know how to test for the endianess of my system, and how to handle it if it's big endian or little endian. Here is my code so far :
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
[Code].....
I need to set a function to a variable of some kind. Then later in the program it needs to run the function that is set to the variable. The variable doesn't need to change after it is set to a function, it just needs to be able to be set to a function. So maybe I don't need a variable? What do I do? :3 Is this even possible? :o
Example:
if (PosRampYes == 0)
{
SomeVariableOrSomething = FirstFunction();
}
else
{
SomeVariableOrSomething = SecondFunction();
}
//later:
SomeVariableOrSomething; //so if PosRampYes is set to 0 then this line would run FirstFunction()