C :: Returning Pointer From Function

Nov 21, 2014

As the title says, i'm using a function which returns a pointer to a struct:

the struct is the following:

Code:
typedef struct POINT
{
uint16_t x;
uint16_t y;
}

Coordinate; the function i'm using:

Code:
Coordinate * Read_XTP2046(void)
{static Coordinate screen;
//calculations to determine the coordinates
screen.x=(temp[1]+temp[2])/2;
screen.y=(temp[0]+temp[2])/2;
// and so on...
return &screen;}

The question is: how do i catch this pointer and make it into a Coordinate struct in which i can read the x and y.

In my main program i would do the following:

Code:
Coordinate cor;
cor = Read_XTP2046();

This does not work, as the function returns a pointer, but how to transform this pointer into a Coordinate struct.

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Dec 10, 2014

I know how to pass a 2-D array to a function. The prototype for that is void f(int (*p)[2]) assuming the array is of integers and there are 2 columns in it.

However, if I wanted the same function to return a pointer to a 2-D array, what would be the prototype?

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Apr 24, 2013

I hear all the time about the rule of not returning a local pointer, but I'm not exactly sure what that insinuates. Would this example be classified as violating that rule?

class Foo {
public:
Bar* ReturnBar() {
Bar* temp = &bars.at(0);
return temp;
}

private:
vector<Bar> bars;
};

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Mar 24, 2015

I am trying to return a char pointer so that i can re use it again. I am writing a vigenere function that takes a message, a key and an initialization vector where it performs the encryption, prints out the encrypted message and returns the encrypted message. I print out the process step by step and everything works, however i pass the answer and print it out again and only the first letter gets changed. I put my code below and my output right after that.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
void decrypt(char *to_encrypt, char *key, char* pct);
enum flag{encryption = 1, decryption = 0};

[code].....

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C++ :: Returning QSharedPointer Or Raw Pointer

May 29, 2014

I have a class which looks like the following:

Code:

class Gadgets {
public:
Data* GetData() const {
return _data.data();
}
const Data * GetDataConst() const {
return _data.data();
}

private:
QSharedPointer<Data> _data;
}

You may ask why i have the second GetData() method that return a pointer to my private member, which will then expose my private member externally. I provide this function just for the case where user can do the following

Code:
Gadgets * myGadgets = new Gadgets();
myGadgets->GetData()->ModifyData(.....);

My question pertains to the use of QSharedPointer of data(), where in the doc, it says

T * QSharedPointer::data () const

Returns the value of the pointer referenced by this object.

Note: do not delete the pointer returned by this function or pass it to another function that could delete it, including creating QSharedPointer or QWeakPointer objects.

Whereas, if i were to use

Code:
Data* data as my private member class instead of QSharedPointer;

I will not need to worry if the caller do as follow

Code:
Data * data = new Data();
Data *data2 = myGadgets.GetData();
data2 = data;
delete data;

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Aug 18, 2014

Should i never return a pointer to a local variable. i have seen the following code in the standard text book.

Code:

struct node *add_to_list(struct node *list, int n)
{
struct node *new_node;
new_node = malloc(sizeof(struct node));
// some code here
return new_node;
}

new_node is a local pointer then why is he returning the new_node? Is it wrong or am i failing to understand something?

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Mar 5, 2013

I have a program that is trying to find all factors of an integer given. It needs to be done in a recursion function. Right now i have code similar to just getting the prime factors of a integer.

unsigned int * find_factors_using_recursion(unsigned int x ) {
unsigned int * factor = new unsigned int[];//do i put x in here ?
for(unsigned int i = 2; i < x; ++i) {
if(x % i == 0) {
find_factors_using_recursion(x / i);
*factor = (factor[i] = i);
} }
return factor;
delete [] factor;
}

When i cout the *factor = (factor[i] = i) it gives me the prime numbers of the integer passed into the function but when I return the pointer it only returns one of the prime numbers. I'm new to c++, how to return pointers from functions that would be great with an example to go with it.

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Jun 22, 2014

So, I've got this class in SDL Player that has, among other things, an SDL_Texture* to hold an image that represents the player on the screen. I'd assume it's good practice to do get() and set() functions for the class; but because textures are handled via pointers, when I write a get() function I end up returning a pointer to an internal resource; which isn't good practice I hear as it "breaks" encapsulation.

Find my code below:

#ifndef PLAYER_H
#define PLAYER_H
#include "SDL.h"
#include "SDL_image.h"
#include "CTexture.h"
class Player {

[Code] .....

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Apr 25, 2014

I am writing a class Player which has several char arrays as private fields. I am trying to write a method which returns an array as a pointer, but doesn't alter the array in any way, thus the const.

Here is a snippet:

Code: class Player
{
private:
char state[MAX_STATE_CHAR + ONE_VALUE];
int rating;
char last[MAX_NAME_CHAR + ONE_VALUE];
char first[MAX_NAME_CHAR + ONE_VALUE];
int groupNumber = NEG_ONE;
public:
char * GetFirst() const
{
return first;
}

Visual studio is saying that the return type doesn't match.

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Mar 14, 2013

I'm trying to call a function via a function pointer, and this function pointer is inside a structure. The structure is being referenced via a structure pointer.

Code:

position = hash->(*funcHash)(idNmbr);

The function will return an int, which is what position is a type of. When I compile this code,

I get the error: error: expected identifier before ( token.

Is my syntax wrong? I'm not sure what would be throwing this error.

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Feb 20, 2015

I am making a game commonly know as the Hangman using C++.

Now I am trying to add a man in it like this:

0
|/
|
/

Now the problem i am facing is that i am using a check that if a function returns the value 0 "return 0" it means the guess is wrong and it will not update the man but if it returns any value there will be a function called which will update the man.

I just wanna know that how i am going to use the check, the kind of thing that i am trying to use is, in general words "if(function returns a value) then update the man"

int main() {
return match;
}

How are we going to use it in check that if int main is returning 'match' in the check...

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This simple little program is not returning a value. The output is

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However, if I go to the function and cout the length, the cout in the main body displays just fine.

Here's the main portion :

cout << "'" << input << "' contains "; //Output of character count.
charCount(input);
cout << " characters, including any spaces.
"; //Output of character count.

and here's the function.

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//Gets the number of characters contained in *string and puts that number into length.

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Mar 7, 2014

Here's a small portion of my program:

Code:
int choice(void) {
char buffer[BUFSIZ];
char answer;
printf("

[Code] .....

I am wondering which is correct to use

Code: return choice();
or
Code: choice();
return num;

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I need to create a function which will print a list from 100Hz to 1000Hz then 1000Hz to 9000Hz. I have created a function in order to calculate and set up the frequency values from 100Hz to 9000Hz using two for loops as shown below. However I am unsure how to return this to the array at the main.

int main(void) {
double Frequency[18];
system ("PAUSE");
return(0); } double Frequency (void)
{
int count;

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Code:
void ThreadA(void const *argument){
uint32_t status = I2S002_FAIL;

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}
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Shouldn't it show an error because x is created locally on stack and gets destroyed on function return?

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I am writing a function to take two vectors and put them end to end in a third vector. I'm new to working with vectors, and I cannot figure out why my append function is not returning vector C. I had the function print out vector C within it to make sure the logic in the function wasn't the problem, and it worked perfectly. My code is as follows:

#include <iostream>
#include <vector>
using namespace std;
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vector <int> c;

[code]....

and my output is as follows:

Vector A contains: 10 18 123 172
Vector B contains: 283 117 17

The two vectors back to back are:

Obviously, the third vector is not returning from the function to main properly, but why.

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Code:
#include <stdio.h>
#define MAXLINE 10
int fgetline(char line[], int maxline);
void copy(char to[], char from[]);
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short int* StartRecord(int seconds)
this is my array :
short int waveIn[NUMPTS];

I'm trying to get the data into an array :

short int arr [] = StartRecord(3);

getting this error: Error2error C2440: 'initializing' : cannot convert from 'short *' to 'short []'

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