C++ :: Having Struct As A Key For A Map

Oct 24, 2014

So why does this not work? As an example:

struct example {
int x; int y;
};
int main() {
example variable;
variable.x = 1;
variable.y = 2;
map<example, int> something;
something[variable] = 3;
return 0;
}

And I get a very long error message from the compiler. I tried using an enum as the key as well and that worked just fine, but I guess that's just the same as having an integer as the key. But anyway, what's the problem with this? Is there any way to make it work?

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C/C++ :: Sizeof (struct) Returns 6 More Bytes Than Actual Struct Size?

Sep 14, 2014

#include <stdio.h>
#define MAX_USERS 20
struct {
char ID[10];
char Name[40];
int Pos;

[Code] .....

I was attempting something weired with address to move data around when I discovered that the size of the array is not what I expected. I am passing this structure as &Users to a function that declares it as a void *, then I can deal with chunks of data (memmove) and not have to worry about index or things like that. However...sizeof is returning something I do not understand.

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C++ :: Creating A Struct Within Struct Node?

Feb 28, 2015

Im having trouble creating a struct within a struct node. the program suppose to hold students firstname, lastname, and gpa in a node therefore creating my linked list. Line 26 keeps saying that cannot convert parameter 2 from 'studentType to std::string

#include <iostream>
#include <string>
using namespace std;
struct studentType{
string firstname;
string lastname;
double gpa;

[code].....

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C++ :: Accessing Inside Structure Via Struct Pointer To Struct Pointer

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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C++ :: Struct Inheriting From A Class Or A Class Inherit From A Struct?

Mar 9, 2012

I just read and have known for a while that classes are private (members and inheritance) by default and structs are public. But my question then comes what if.. a struct inheriting from a class or a class inheriting from a struct?

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C :: How To Use Pointer To Struct

Mar 6, 2015

how can I call and print the Pointer:

ptr->address
Code: #include<stdio.h>
struct account {
int address;
int value;

[code]....

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C :: How To Do Search In Struct

Jul 9, 2014

So i create a simple structure,that has a firstname, lastname, age, dateofbirth.I would like it if i type what I am searching for print out there is one or not.But i have some trouble with equals(in array).. i type in the same "keresettnev" as "tanulok[i].Firstname" but it thinks not the same. (it works with age..)

Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct student {
char *Firstname[40];
char *Lastname[40];
int age;

[Code] ....

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C :: Why Zero Out Rest Of The Struct

Jun 19, 2014

I am using Beej's Guide to Network Programming Using Internet Sockets. I'm just curious why I need to zero out the rest of the struct?

Code:

int main(){
int sockfd;
struct sockaddr_in my_addr;
sockfd = socket(AF_INET, SOCK_STREAM, 0);

[Code].....

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C :: How To Printf A Struct

Apr 22, 2014

Code:

#include <stdio.h>
struct database {
int id_number;
int age;
float salary;

[Code] ....

When I compile, I get an error:
test.c|18|error: incompatible type for argument 1 of 'printf'|
note: expected 'const char *' but argument is of type 'float'|

I thought employee.salary is a float but the compiler expected 'const char'. How do I make this work?

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C++ :: How To Alias Struct

May 7, 2013

I am working on a program which uses external hardware to acquire data. we have the option to use hardware from two different companies, each with it's own driver. However both do the same job. My program is meant to read data packets which are structured as:

typedef struct _data {
DWORD ID;
BYTE bf;
BYTE bd;
BYTE bData[8];
DWORD bt;
} data;

Now both the companis use the same data structure, but the first has defined the structure, let's say, as:

typedef struct _dataX {
DWORD ID_X;
BYTE bf_X;
BYTE bd_X_;
BYTE bData_X[8];
DWORD bt_X;
} dataX;

[code].....

I am programming my software so as t allow the customer to use the hardware of their choice. Simply select the card they are using and our program should be able to take care of the rest of stuff. I am using #ifdef directives to include the header for the corresponding hardware dll. Now I want to define my own data struct of the type:

typedef struct _dataMY
{
DWORD ID_MY;
BYTE bf_MY;
BYTE bd_MY_;
BYTE bData_MY[8];
DWORD bt_MY;
}

[code]....

and when I use _dataMY.ID_MY .. it should directly be able to see if it is _dataX.ID_X or _dataY.ID_Y, based upon the directive I have used earlier.

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C++ :: Going From Struct To Class

Jun 21, 2014

I've been working on a path-tracer for some time, and all along I've used structs instead of classes for vectors and matrices. Today I changed all of them to classes instead, changing none of the actual function bodies themselves, and the results were miserable to say the least.

Here's a render form before the change: [URL] ....

And here's the same render after: [URL] ....

Why this is happening, considering that none of the actual function-bodies have been changed, except for what little is needed to make the change from class to struct.

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C++ :: Iterating Through Struct Members?

Apr 4, 2013

Suppose I have a struct with 20 members. I want to assign each of those structs with values. Instead of accesing by explicit convention, i.e.:

Code: struct.member1 = 1;
struct.member2 = 2;
...
...
...
struct.member20 = 6;

Is there any way to encapsulate it in a for loop and use an iterator variable to indicate the member? i.e.:

Code: for (int i = 0; i < 20; i++)
struct.i = i;

The above is pseudocode but Im sure you get what Im trying to do?

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C++ :: Outputting Associated Data In Struct

May 2, 2013

So this is the last part of a program I've been working on for four weeks now. This question may be a tough one considering the amount of files included in the program.

The program is to read in a file of requests between two cities, read in a file of flights and cities that occur between the cities. It then checks to see if there is a path between the flights and output an itinerary. I have the correct itinerary outputting, but when attempting to output the associated flight number and price according to the city, I am getting odd data. How can I output the correct flight number and price associated with each flight on the itinerary.

I'll post out the output I am currently getting and the section where I am outputting the data. I'm sure I'll need to post more files so the program can be understood.

Don't want the code done for me, just a point in the right direction! I don't want to let this program defeat me!

Output: Code: Request is to fly from Atlanta to San-Diego.The flight itinerary is:
Flight # From To Cost
10 Atlanta Chicago $134529069
10 Chicago Miami $134529069
10 Miami Dallas $134529069
10 Dallas San-Francisco $134529069
10 San-Francisco San-Diego $134529069
This function finds a path between cities. Code: bool flightMap::IsPath(string originCity, string destinationCity){
StackClass aStack, bStack;
flightStruct flightRec;
string topCity, nextCity;
bool success;
int index = 0;

[Code].....

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C :: Array Of Pointers To A Struct?

May 10, 2013

I 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:

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C :: Copy Of Struct Not Working

May 14, 2013

Code:
#include <stdio.h>
#include <stdlib.h>
typedef struct BOOK
{
int* price;
} Book;

[Code] ....

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C :: Integer In Struct Equals Zero Later

May 15, 2013

Code:
/*
* Instruction_t - stores a specific instruction
*/
typedef struct
{
[code]....

I have a problem. When I run my program (which contains this), through gdb, I can see that burstTime does have a value ( such as 1, 3, 15, etc).But when I dequeue from my list, instruction->burstTime suddenly equals zero!

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C# :: Package Methods In Struct

Oct 20, 2012

Is it common practice to package methods with other elements(string-s, int-s, float-s, array-s...) of struct?

Than struct acts as a class or is acting similar to class and that have no sense to me? I am new to OOP .

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C :: Writing A Struct To A File

Sep 28, 2013

I am trying to write a structure to a file. Example say the structure has two variables x and y . I want to write a function which modifies these variables and stores the modified version on a file. Such that next time I call the function . it has the values from the previous write. Here's an example of my code .

Code:
// initialize the structure struct->x = 0, struct->y = 0
File *fp = fopen("filename", "r+");
struct MYSTRUCT mystruct = (struct MYSTRUCT*)malloc(sizeof(MYSTRUCT))

//check
fread (mystruct, sizeof(MYSTRUCT), 1, fp);

// do some calculations.
fwrite(mystruct, sizeof(MYSTRUCT), 1, fp);
fclose(fp)

//return some value
}

The problem is that each time I run the program it shows the initialized value of the variables and not the value from last write. I guess the write isn't successful because when I open in w+ mode. i get the error file could not be opened and then i have to delete the file and re create it....

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C :: Aligning Struct To A Page

Nov 22, 2014

I am a bit unsure about what this piece of code aligning a struct to a page is trying to achieve.

Code:
#define PAGESIZE 1 << 12

typedef struct __attribute__((aligned(PAGESIZE))) x86_pagetable {
x86_pageentry_t entry[PAGETABLE_NENTRIES];
} x86_pagetable; It is an piece of code from an educational operating system WeenyOS.

What is the essence of aligning a struct to a page?

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C :: Passing Struct Through Array

Apr 2, 2013

I am trying to pass a struct through an array to another array from one microprocessor to another microprocessor and then dereference that array to update the same exact struct on the other microprocessor.My goal is to always have values inside of both structs while sending any updates to the struct on the other microprocessor in the mean time but I seem to be looping through the data and the members of the struct seem to be cleared out after every clock cycle. I can verify this by the flashing of my leds which the struct controls.

FIRST MICROPROCESSOR

Code:

extern struct i2c_data * TX_Data;
extern struct i2c_data TX_Data_1;
extern struct i2c_data TX_Data_2;
}

[code]....

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C :: How To Print Struct From Another Function

Oct 31, 2013

how to print struct from another function? let's say I have code this way

Code:

struct student{
int id // simple example
};
main(){
modify_data(); // calls the function.
}

[code]....

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C++ :: How To Tell Function Which Part Of Struct To Use

Jul 4, 2013

Say I have a structure defined as such:

struct data{
char c;
int x;
};

And I want to create a function to print either c or x. However, I don't want to just use a switch or something to figure this out, I want to reference which part I'm outputting.

Now here's the twist

vector<data> dataList;

I need to access element x or c in the vector, but all I pass is the vector and which element, so that I might have something like:

void (vector<data> x, DataType i){
cout << x[0].i;
}

So now, if I pass either x or c (someway), I can output one of them.

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C++ :: Stack Implementation With Struct

Apr 7, 2014

I am trying to implement a stack class which has struct data type as its private member. I am getiing the following error ,

bash-3.2$ g++ stack_str_arr.cpp
stack_str_arr.cpp: In member function ‘void stack::push(int)’:
stack_str_arr.cpp:39: error: ‘top’ was not declared in this scope
stack_str_arr.cpp: At global scope:
stack_str_arr.cpp:43: error: no ‘void stack::display()’ member function declared in class ‘stack’

Code:

#include<iostream>
using namespace std;
#define MAX 5
class stack {
public :
stack();

[Code] ....

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C++ :: Array Of Struct Initialization

Apr 4, 2014

In a book I'm reading, the author has the following struct:

struct VertexPos {
XMFLOAT3 pos;
};

Where XMFLOAT3 is a structure with x,y,z floating point values within. He declares and initializes an array as the following.

VertexPos vertices[] =
{
XMFLOAT3(0.5f, 0.5f, 0.5f),
XMFLOAT3(3.3f, 5.6f, 3.6f),
XMFLOAT3(-4.5f, 2.2f, 6.4f)
};

It doesn't make sense to me why this is working. The way my mind is thinking about this is that vertices is an array of type VertexPos, so then why can it be initialized with objects of type XMFLOAT3?

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C++ :: Size Of Struct Program

Dec 14, 2014

I'm having trouble figuring out how to find the size of an array program that involves "struct."

#include <iostream>
using namespace std;
struct d{
char* a;
float b;
int c;

[code].....

When I run this program, the output is 80(for my compiler). That would mean that each element in the array is 16 bytes but I don't understand how struct d is 16 bytes.

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C++ :: Size Of Result With Struct Var

Apr 20, 2013

typedef struct Element Element;
struct Element {
char x;
double* y;

[Code] .....

This one with y pointer gives 8

typedef struct Element Element;
struct Element {
char x;
double y;

[Code] ....

This one with a normal y variable gives 12

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