C++ :: Classes Defined With Struct And Union
Mar 12, 2013
Classes defined with struct and union
Classes can be defined not only with keyword class, but also with keywords struct and union.
The concepts of class and data structure are so similar that both keywords (struct and class) can be used in C++ to declare classes (i.e. structs can also have function members in C++, not only data members). The only difference between both is that members of classes declared with the keyword struct have public access by default, while members of classes declared with the keyword class have private access. For all other purposes both keywords are equivalent.
The concept of unions is different from that of classes declared with struct and class, since unions only store one data member at a time, but nevertheless they are also classes and can thus also hold function members. The default access in union classes is public.
The above is a statement taken from a C++ tutorial. So I understand classes a bit better now but the above quote doesnt make too much sense. Is it saying that you can have a class within a class?
View 1 Replies
ADVERTISEMENT
Mar 17, 2013
I am getting a compilation error from the code below. It is when i am naming a variable with my user defined type.
#include<iostream>
#include<cstring>
#include<cstdlib>
using namespace std;
class person {
[Code] .....
C:Dev-CppTRIAL.PASS.!!!.cpp In function `int main()':
66 C:Dev-CppTRIAL.PASS.!!!.cpp expected primary-expression before "p"
66 C:Dev-CppTRIAL.PASS.!!!.cpp expected `;' before "p"
74 C:Dev-CppTRIAL.PASS.!!!.cpp `p' undeclared (first use this function)
(Each undeclared identifier is reported only once for each function it appears in.)
83 C:Dev-CppTRIAL.PASS.!!!.cpp `X' undeclared (first use this function)
View 4 Replies
View Related
Oct 17, 2012
I have a basic vector/point class where I've overloaded a bunch of arithmetical operators:
Code:
#pragma once
class point {
public:
point() {
}
point(float p_x, float p_y, float p_z) : x(p_x), y(p_y), z(p_z)
[Code] ...
I can use it fine like
Code:
point p(50,50,50);
point q(50,50,50);
point t = p * q + q;
However when I put this point type into a struct and try to access the members after passing it through by const reference:
Code:
struct sextic {
point a,b,c,d,e,f,g;
};
inline static sextic sexticDifference(const sextic &p_sextic1, c
[Code] ....
This gives me an "operator not defined" error for compilation.
View 2 Replies
View Related
Apr 16, 2013
I am trying to create a class type structure using struct instead of classes.
Code:
#include <iostream>
#include <stdlib.h>
using namespace std;
struct myclass {
int * array;
int nelements;
[Code] ....
Guess what I am asking is using the pointer in the first code section better or is there another way'. I don't know about making the second code work.
View 3 Replies
View Related
May 27, 2013
I'm trying to use a structure in union in the following format:
Code:
union data
{
unsigned char All[10] ;
struct data_pkt
{
unsigned char ack;
unsigned short status;
unsigned short data_length;
unsigned char Data[5];
}format;
}adb; adb.
All has 10 bytes which is equivalent to the structure bytes. ie 6 bytes if unsigned char and 2 short i.e 4 bytes. Thus total 10 bytes is given to adb.All. When I print the struct size I get 12 bytes. This creates problem in obtaining data in union. According to the program:
adb.format.ack should have the address of adb.All[0]
adb.format.status should have the address of adb.All[1]
adb.format.data_length should have the address of adb.All[3]
adb.format.Data[0] should have the address of adb.All[5]
But in actual case this is how memory is allocated:
adb.format.ack assigned to the address of adb.All[0]
adb.format.status assigned to the address of adb.All[2]
adb.format.data_length assigned to the address of adb.All[4]
adb.format.Data[0] assigned to the address of adb.All[6]
Why this is happening? How can I solve this?
View 9 Replies
View Related
Nov 16, 2013
How I could use unions to combine registers elegantly. For example I have the 8 bit registers B and C & I have opcodes that work on each independent register such as add b, c, which is simple, but then I also have opcodes that work on both of them as if they're one like ld a, bc. I know I could go about that by just masking them together but I've seen it done with unions before & it made everything so much more simple.
View 4 Replies
View Related
Jul 2, 2013
In the current code,We are using pointer of union and assigning value.
class sample {
union {
short *two_int;
int *four_int;
double *eight_real;
char *one_ascii;
// void *v;
}; }
Than we assign value in following way.
sample.four_int[0] = (x + xoff); ( x and xoff and y and yoff all are integer)
sample.four_int[1] = (y + yoff);
Than we write data into file. it was working fine into 32 bit machine but it is not working 64bit machine. When I compare data and found that data is divided by 4. For Ex The File generating from 32 bit machine contain 80 than 64 bit . File contain 20.
View 7 Replies
View Related
Sep 1, 2013
I have made VGA emulation with registers and memory in my emulator. But for some reason the writes to the union array with CPU data (register 0-8 of the VGA's Graphics Controller Registers, referenced with <GRAPHREGS>.DATA[index]) don't reflect on the union's data.
typedef union __attribute__((packed)) {
byte DATA[9]; //9 registers present!
struct //Contains the registers itself! {
//Set/Reset Register (index 00h)
union {
[code]...
what's going wrong? Have I made an error in the registers?
(In this case I write to register <GRAPHREGS>.DATA[8] (which should be the <GRAPHREGS>.REGISTERS.BITMASKREGISTER)), but the BITMASKREGISTER stays 0, while DATA[8] gets the correct value.
View 4 Replies
View Related
Sep 10, 2012
I have the following C++ code
typedef union UUID {
unsigned char byte[16]; /**< Array of 16 bytes. */
unsigned int ll[2]; /**< Array of two 64-bit words. */
} UUID;
[Code] ......
The compiler complains thus
$ g++ union.cpp
union.cpp: In function "int main()":
union.cpp:15:17: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x
union.cpp:15:17: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x
union.cpp:15:17: error: no match for "operator=" in "entry.EntryHeader::uuid = {0, 0, 0, 2}"
union.cpp:1:20: note: candidate is: UUID& UUID:perator=(const UUID&)
How do I go about assigning values to this union in C++.
View 3 Replies
View Related
Oct 5, 2013
I have an array of (Student)classes created in Manager.h, which contains a new instance of class Name (name),(in Student.h)How would I go about accessing the SetFirstName method in Name.cpp if I was in a class Manager.cpp? I have tried using Students[i].name.SetFirstName("name");
// In Manager.h
#include"Student.h"
class Manager
{
[Code]....
View 2 Replies
View Related
Mar 6, 2015
What i'm interested in is the behavour of a struct/union constructed like this:
Code:
typedef struct {
uint64_t num1;
uint64_t num2;
} st_a;
typedef struct {
uint64_t num1;
uint32_t num2;
[Code] .....
What kind of behavour could I expect from object, in the following cases:
1. newsomestruct(0)->u.a.num1 = 2;
2. newsomestruct(1)->u.b.num1 = 2;
3. newsomestruct(0)->u.a.num2 = 2;
4. newsomestruct(1)->u.b.num2 = 2;
5. newsomestruct(0)->u.b.num1 = 2;
6. newsomestruct(1)->u.a.num1 = 2;
7. newsomestruct(0)->u.b.num2 = 2;
8. newsomestruct(1)->u.a.num2 = 2;
9. Code:
somestruct* ss1 = newsomestruct(0);
somestruct* ss2 = newsomestruct(1);
* ss1 = * ss2; 10. Code: somestruct* ss1 = newsomestruct(0);
somestruct* ss2 = newsomestruct(1);
* ss2 = * ss1;
This is what I'd expect, but I can't find any evidence online in C standards or elsewhere:
1. Works as expected, sets the value of a.num1 to 2.
2. Works as expected, sets the value of b.num1 to 2.
3. Works as expected, sets the value of a.num2 to 2.
4. Works as expected, sets the value of b.num2 to 2.
5. Works as expected, sets the value of b.num1 to 2.
6. Works as expected, sets the value of a.num1 to 2.
7. Works as expected, sets the value of b.num1 to 2.
8. Crashes/Memory Corruption, attempted to alter memory outside struct.
9. Works as expected, * ss1 == * ss2
10. Crashes/Memory Corruption, attempted to alter memory outside struct.
I've tested simular code on my machine (Xubuntu 14.04LTS compiled with gcc on -O3) and it appears to be reliable, given that you stick with acessing the type tagged in the struct or the common initial union struct members (in this case num1).
View 6 Replies
View Related
Jul 5, 2013
I have union of pointer.
union {
short *two_int;
int *four_int;
double *eight_real;
char *one_ascii;
// void *v;
};
We have write function which write into file.
fwrite (r.one_ascii, 1, i, outstr);
I found one thing,When we write function, we fill only four int in following way.
r.four_int[0] = x + xoff;
r.four_int[1] = y + yoff;
So my question,we fill four_int but write one_ascii only.As is it union of pointer. So it does not matter. I am using 64bit machine and do not have any issue in 32 bit machine.
For more information: [URL] ....
View 7 Replies
View Related
Jan 16, 2015
how to find out which member of union is currently set/active.
exm:
union myunion{
int i;
float f;
}
if i set myunion ob{7}, it set ob.i=7;
my q? is how to find out i is set f is not set/ not acrive
View 2 Replies
View Related
Jun 19, 2014
It involves some discrete mathematics. Any code snippet to get me started?
View 3 Replies
View Related
Feb 17, 2014
The program is to find intersection,union and difference of two sets. The program take the input correctly but after it crashes with the message that some exe is not working...
Code:
#include<iostream>
using namespace std;
void Input(int *A, int*B, int size1, int size2)
//input function {
[Code] ....
View 3 Replies
View Related
Apr 30, 2014
I'm trying to come up with the union of two Vector ADT bags, so I have to overload the '+' operator, but I'm getting a bunch of error messages saying:
VectorBag.cpp: In instantiation of ‘VectorBag<ItemType> VectorBag<ItemType>::operator+(VectorBag<ItemType>) [with ItemType = int]’:
proj2.cpp:161:42: required from here
VectorBag.cpp:81:24: error: no match for ‘operator[]’ (operand types are ‘VectorBag<int>’ and ‘int’)
newBag.add(anotherBag[i]);
^
Here is the function to overload the operator:
template<class ItemType>
VectorBag<ItemType>
VectorBag<ItemType>::operator+(VectorBag<ItemType> anotherBag) {
VectorBag<ItemType> newBag;
for (int i = 0; i < anotherBag.getCurrentSize(); i++)
newBag.add(anotherBag[i]);
}
The add() function is pre-defined by me somewhere else in the code. It basically does push_back().
View 4 Replies
View Related
Jul 15, 2014
I'm trying to union eleven tables to call out data. Parent table is 'Events', child tables are 'SR1Laptimes', 'SR2Laptimes' and so on (there are ten SR... tables). Primary key in all tables is EventName. Parent/Child relationship is Events.EventName/SR1Laptimes.EventName etc All tables that start with SR have the same Schema. I'm trying to call out MIN(Q1) across all table but first need to Union them I believe. Here is my code.
myCommand.CommandText = "SELECT MIN(Q1), MIN(Q2), MIN(Q3), MIN(Q4), MIN(LaptimesMinutes), MIN(LaptimesSeconds) FROM (SELECT * FROM Events UNION ALL SELECT * FROM SR1Laptimes UNION ALL SELECT * FROM SR2Laptimes) WHERE (Events.Track = @track) AND (Events.Number = @number) AND (Events.Rider = @rider)";
myCommand.Parameters.AddWithValue("@track", analysisTrackComboBox.Text);
myCommand.Parameters.AddWithValue("@number", analysisNumberComboBox.Text);
myCommand.Parameters.AddWithValue("@rider", analysisRiderComboBox.Text);
View 4 Replies
View Related
Dec 27, 2012
I have some problem while allocating memory to a union inside structure. Below is the code i am using
ON SYSTEM1:
This works fine
ON SYSTEM2:
compiler complains saying "need structure or union type" while allocating MYSTRUCT1.
If I change:
shreyas[0].UnionAttr.struct1 = (MYSTRUCT1 *) malloc (sizeof(MYSTRUCT1)
to
shreyas[0].UnionAttr->struct1 = (MYSTRUCT1 *) malloc (sizeof(MYSTRUCT1)
This compiler on SYSTEM2 is happy. but second way does not look correct to me and compiler on system 1 complains about it. Which is the correct way to allocate memory?
If first one is correct then what should i look in for to avoid this error? Could this be an issue with compiler on SYSTEM2? If i use second method on SYSTEM2 code segfaults during malloc.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct mystruct1 {
int a;
int b;
[Code] ....
View 3 Replies
View Related
Jan 16, 2013
I am currently working with win32 API , for image processing, one of the windows function returns RGBA ( colors ) as unsigned int , I then split it into individual bytes by creating a union ,
Code:
union colour {
unsigned int value;
unsigned char RGBA[4];
}
to spit the int into individual bytes, my Question is there a better or my convenient way of doing this.
View 6 Replies
View Related
Mar 27, 2013
Any way that one could create a bitfield using the standard technique of creating a structure within a union, as follows:
Code:
typedef union {
struct {
unsigned b0 : 1;
unsigned b1 : 1;
:
:
unsigned b(n-1) : 1;
} bits;
unsigned int value;
}
BIT_FIELD_TYPE; Except, what I'd like to do is to replace all the single-bit elements in the bits structure with a single statement that creates an array of, say, 32 values. The clear advantage of this is that it could be traversed using an iterator, ...
Code:
main() {
BIT_FIELD_TYPE foo;
unsigned int i;
...
for (i = 0; i < n; i++) {
... (print out foo.bits.b[i]) ...
}
So far, I've not figured out a way to do it, either as an array, or using a pointer to iterate through the individual bits.
View 6 Replies
View Related
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.
View 9 Replies
View Related
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].....
View 2 Replies
View Related
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.
View 3 Replies
View Related
Sep 16, 2013
What I want to do is have a defined string as the input and use that to run it against the keys, so I can pull out the values. I have some functions beneath for searching, a possibility would be to parse the input and use something along those lines.
I would like to try and use a map for this.
#include <iostream>
#include <map>
#include <string>
[Code].....
View 6 Replies
View Related
Feb 26, 2013
I'm making my way through most of this assignment that I have, but now it seems like I've run into a bit of a roadblock. The issue that I'm having is not being able to printf a series of ints that I thought I had previously defined in another function. I don't want to clog up this post with the entire code, so I'll just post one function that defined an int to give an example. I will upload the whole thing upon request however.
Code:
#include <stdio.h>
#include <stdlib.h>
//Prototypes
int AGrade1(int* grade1);
int AGrade2(int* grade2);
int AGrade3(int* grade3);
[Code] .....
I've tried many many things, but I just cant figure it out. This is what it's supposed to look like.
Assignment Grades:
18 12 17 15 20 13
20 18
View 9 Replies
View Related
Jan 16, 2015
Say I have something lke
Code:
#define FOO BAR
#if FOO == BAR
doX();
#else
doY();
#endif
This causes doX(); to be executed. But the intent is to have doY(); be run. I'm guessing this is because BAR is undefined and therefore blank, so blank equals blank. Is there some way to compare the symbol FOO was set to instead of its value, BAR?
View 4 Replies
View Related
