C :: Passing Structure Pointer To A Function
Aug 24, 2014
I am trying to wright a program that takes student grade data from a command line file, calculates a final grade, and copies the final grades to an output file. So far I have two functions, one that creates a student structure by allocating memory for it and returning its address, and one that should take that address and fill it with data from a line from the input file. My ultimate goal is to use a linked list to connect all the structs, but for now I just want to get the functions working. When I run what I have so far, I get an error C2440 (using visual 2010) that says "cannot convert from 'cStudent *', to 'cStudent', and points to the line where I call my fill function. How should structure pointers be passed?
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct student // Declaring student structure globally.
[Code] .....
Also, here is a sample of what a line from the input file would look like:
Bill Gates, 60, 54, 38, 62, 65, 60, 50
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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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Jun 22, 2013
Is there a way of passing values gotten from a function into a fields of a struct?
Lets say you got a function that returns sum and square of some numbers. How can I assign those values to the new made struct?
struct Struct
{
int sum_from_func;
int square_from_func;
};
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Feb 27, 2014
I've been able to write the program completing all requirements except for one... creating a function that accepts a nested structure array. Here's the program:
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
struct PayInfo {
double hours; // Hours worked
double payRate; // Hourly payRate
[Code]...
I don't even know where to begin. Specifically, concerning all the aspects of the function.
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Jan 3, 2015
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].....
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Sep 7, 2013
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_CMD_LINE 500
void tokenize(char *cmd_ln, char *fun_tknzd[], int *argument_cnt);
[Code] ....
I am trying to pass the value of fun_tknzd to str_tknzd
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Oct 14, 2014
I'm trying to pass the pointer of a dynamic array into a template function, but it keeps telling me there is no matching function to call because the parameters I'm passing in are wrong. how to make the function accept the pointer.
//main
int main()
{
srand(unsigned(time(NULL)));
int size;
int *list;
int *listCopy;
[code].....
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Apr 24, 2014
I can clearly understand how to pass a dynamic array to a function and modified within the function..
My aim is to get back the array initialized as I am trying on the next sample of code..
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <iostream>
#include <fstream>
using namespace std;
#define N3//number of bodies
void initialise( double *M[], double *X[], double *y[])
[code]....
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May 20, 2014
I have a Qt classes as follow:
Code:
class Vehicle {
public:
void AddData(QString str, Data* data) {
_myDataMap.insert(str,data);
} virtual void Init();
[code].....
My questions are:
After the main function called d1->Modify; the data stored in _myDataMap will get modified too.
What is the more appropriate way of passing the Data through AddData in such case?
If i do AddData(const Data & data), i will not be able to use inheritance of Data, i.e passing a subclass of Data to AddData.
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Mar 7, 2014
Is there such thing as passing a winforms label by reference? For example, can I create a pointer label and pass the address to a function? I've looked online but couldn't find anything. Perhaps that's a sign?
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Dec 4, 2013
I have this code:
#include "stdafx.h"
#include <iostream>
using namespace std;
void square_cube(float *x,float *y) {
[Code] .....
The function should pass the square of the first input parameter and the cube of the second input parameter back to the calling routine. I thought I could use a recursion but its not going to work.
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Sep 14, 2013
I am getting a few compile errors for what might be a simple thing to do. I am opening a file in main, passing that pointer to a function and checking the contents of that file with a regex before I pass it on to build a BST. I am getting the following compile errors, what is wrong. Here are the errors:
Code:
gcc main.c fileCheck.c -o tree
main.c: In function `fileCheck':
main.c:19: error: syntax error before "FILE"
fileCheck.c: In function `fileCheck':
[Code] .....
Fatal error: Command failed for target `tree' Here is the two files and header that seem to be causing me the problems.
main.c
Code:
#include "main.h"
//#include "node.h"
int main(int argc, char *argv[])
FILE *fp;
if (argc > 2)
[Code] ....
And the header file.
main.h
Code:
#ifndef MAIN_H
#define MAIN_H
#ifdef __cplusplus
extern "C" {
#endif
[Code] .....
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Aug 15, 2012
I have in the past written code for templated functions where one function argument can be either a function pointer or a Functor. Works pretty straightforward.
Now I am in a situation where I am actually trying to pass a function pointer as template argument to a class. Unfortunately this does not work, I can pass the Functor class but not the function pointer. Below code illustrates the issue:
Code:
#include <string>
#include <iostream>
#include <sstream>
#include <cstdlib>
// For demonstration
const char * external_library_call() {
return "FFFF";
[Code] .....
The idea is to have the definition of the Record class simple and readable and have a maintainable way to add auto-conversion functions to the class. So the lines I commented out are the desirable way how I want my code to look. Unfortunately I could not come up with any way that was close to readable for solving this.
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Oct 27, 2013
I am working on a project and decided to try something simple before I start adding items. I am calling a function from main and that function has a file pointer.
Here is my main.cpp
Code: #include <cstdio>
#include <string>
#include <iostream>
#include "main.h"
extern FILE *fp;
using namespace std;
int main(int argc, char *argv[])
[code]....
Here is the function:
Code:
#include <string>
#include <cstdio>
#include <iostream>
#include "main.h"
[Code] ....
My test file consists of several characters and digits. Nothing special and I at this point in time do not have any type of formatting that needs to be adhered to. I am simply wanting to read the file character by character and print it out. When I run the program, I get this symbol:
Code: If I use a printf statement, such as:
Code: printf("%s
", nextChar);
I get a segmentation fault.
My main.h Code:
#ifndef MAIN_H
#define MAIN_H
void scanner(FILE *);
//char getChar(FILE *);
#endif and lastly my scanner.h Code: #ifndef SCANNER_H
#define SCANNER_H
FILE *fp;
#endif
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Sep 19, 2014
Basically I'm trying to pass an object as a reference to the template function, rather than a copy as it's seeing. I'm needing to do this without editing Obj::Call to accommodate a reference as its first parameter, as it'd break other calls.
You'll notice in the following code the object will be destroyed upon passing, while the object defined is still in-scope due to the infinite end loop.
#include <iostream>
#include <string>
using namespace std;
class Obj {
public:
string name;
Obj(string name): name(name) {cout << "create " << this << endl;}
[code]....
In the past I tried ref(), which appeared to stop this happening, however it created a blank copy of the object instead.
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Dec 7, 2014
Why doesn't this compile?
struct hi(){
void other();
}histructure;
void hi::other(){
std::cout << "Hi!" << std::endl;
[Code] ....
Makes no sense the structure is written before the structure member function is called so why is there compile errors ??...
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Jun 4, 2013
Code:
#include <stdio.h>
#include <stdlib.h>
int size_b_row1;
int size_b_col1;
[Code].....
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Jun 4, 2013
#include <stdio.h>
#include <stdlib.h>
int size_b_row1;
int size_b_col1;
int main(void) {
double C[4][4] = {{1,3,5,2},{7,6,2,2},{1,2,7,3},{2,3,5,3}};
double TC[4][4];
transpose(C, TC);
[Code] ......
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Oct 31, 2013
Description: Use functions and structures to simulate storage in a warehouse
*/
#include <cstdlib>
#include<iostream>
#include<cmath>
#include<iomanip>
#include<string>
using namespace std;
struct Bin {std::string name; int Quantity;}; //create a structure for "Bin"
[code].....
I keep getting a linker error on every function. what am I doing wrong?
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Mar 20, 2014
What this is, is a more recent assignment and my question is if my errors are directly related to passing structure addresses to functions. I've tried several syntax variations at the beginning of my loops such as this one:
while (choice != "Q" || "q")
But the loops will not run since I introduce polar to rectangular and the choice element. My last working code was rectangular to polar and all of it worked fine.
#include<iostream>
#include<cmath>
using namespace std;
//structure declarations
struct polar
{
double distance; //distance from origin
double angle; //direction from origin
[Code] ....
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Nov 28, 2013
Program to create client server interaction for store data into map using structure and pointer(without memory leak).
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Jun 5, 2012
"
#include <stdio.h>
struct datastructure {
char character;
};
void function(struct datastructure** ptr);
[Code] ....
These codes give these errors:
error: request for member 'character' in '* ptr', which is of non-class type 'datastructure*'
error: request for member 'character' in '* ptr', which is of non-class type 'datastructure*'
These errors are related to
"
*ptr->character='a';
printf("Ptr: %c",*ptr->character);
"
I want to access "character" data inside the structure "trial" by a pointer to pointer "ptr" inside function "function",but I couldn't find a way to do this.
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Sep 2, 2014
Is there way to find the size of structure pointer size? When we tried to get the size of structure pointer will get size of address(@ location) which would be 4 bytes long. But I want to get the size of all structure members size using structure pointer.
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Sep 16, 2014
const free_throws & clone(free_throws & ft) {
free_throws * pt;
*pt = ft; // Copy info
return *pt; // return reference to copy
}
This is a code snippet extracted from C++ Primer Plus book. However, it is really confusing. I don't really understand the free_throws * pt;
as far as I know, a pointer has to point to a memory address, and it is best to initialize it when it is declared. However, according to the code snippet above, the pt isn't initialized to any address. Isn't it dangerous when we declare a pointer without initializing it before we use it?
I thought it is supposed to be like this
free_throw * pt = new three_throw;
// or
free_throw * pt = & ft;
BTW, free_throw is a structure.
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Jan 22, 2015
I need to know how to access the nested structure using pointer, i mean i know how to do that when i have simple structure, for example:
Code:
struct person{
char fname[16], lname[16];
int age;
}
for this example i can use
Code: (*pointer).age
or
Code: pointer->age
But if i have structure like this:
Code:
struct date{
int day, month, year;
}
struct person{
char fname[16], lname[16];
struct date birthDate;
}
Then how can i access the birthDate using pointer?
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Aug 5, 2014
I have written this program
Code:
#include <stdio.h>
#include <string.h>
int main(void) {
struct point {
[Code] ....
error: request for member is not a structure or union
printf("%d
,%d
",p1->i,p1->j);
I was just trying to typecast a integer pointer to structure pointer, but throws error as shown.
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