This is a function that is supposed to add two different arrays containing 9 items together, but it has a problem when it comes to doing any actual adding.
Code:
int * add_data(int x[], int y[], int z[])
{
int i;
char a[9];
for (i=1;i!=9;i++)
{
printf("%d =x
", x[1]+y[1]);
x[1] + y[1]= a[1];
}
return a;
}
I am new to c++ programming and i have written a simple class program to display the name and duration of the project
#include<iostream>
class project {
public:
std::string name;
int duration;
};
[Code] ....
Now i am trying to the write the same program with the usage of member functions using set and get member functions. i have tried the following
#include<iostream.h>
class project {
std::string name;
int duration;
// Member functions declaration
[Code] ....
I am not sure whether above code logic is correct, how to proceed with it.
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?
How to access the name and file name members on line 42 and 43?
Code:
typedef struct {
char * name;
char * filename;
} FILES;
FILES * files[256];
}
[code]...
How to access the name and filename from within function?
*files[count].name = chTmp;
I want to define a class, which will have two members, for example, vaporPressureStatus and vaporPressure
enum vpStatus_t {nonesense, unknown, known, saturated};
class pore_t {
public:
vpStatus_t vpStatus;
double vaporPressure;
};
when vpStatus is nonsense and unknown, the vaporPressure should not have a value; and if I calculate out a value for vaporPressure, the vpStatus can be set as known.
I am wondering if there is any set, pair or other structure can hold this two members together, so that when I change one's value, the other guy will also change accordingly.
I am versed in qsorting struct members within a struct instance, as in the example below:
Code:
#include <iostream>
#include <stdlib.h>
using namespace std;
struct item_database {
[Code]....
What I CANT do however is to sort an array of structs by one of its members. This is a complete different problem even if it sounds similar.
In other words, the problem is this; Say we have a struct:
Code:
struct item_database {
int key;
string token;
};
Then we declare an array of this struct in the heap:
Code: item_database *idptr = new item_database[700000]; and initialize its values.
How would one go about sorting this heap array of structs by its member function "token"?
I used the following call to qsort (standard library) and call to the compare function but it doesnt work:
Code:
qsort (idptr, 1000, sizeof(string), compare);
Code: int compare (const void* a, const void* b){
if (*(char*)a >= *(char*)b)
return 1;
else
return -1;
}
Or in more lamens terms say we have the following stuct instances:
Key: Token:
1 Hello
2 World
3 How
4 Are
5 You
Then I need those structs to order according to token (alphabetically, increasing or decreasing depending whats in our compare function).....
files.c
Code:
#include "include/types.h"
#include "include/gaussian.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
[Code]....
I need to access the members .name and .filename to allocate memory and copy strings in there.
Code:
files[count]->name=malloc(64);
files[count]->filename=malloc(64); SIGSEGV error
How to make the reference working?
I am trying to pass multiple args to g_signal_connect through a struct and it's members. I think the problem lies with execlp. I am trying to pass the struct members to it but I keep getting errors. No matter how I format execlp and the struct args, I always get an error. The current error I receive is Bad address. Like I have said before, no matter how I format execlp, I receive some sort of error.
Code: /*
Compile me with:
gcc -Wall sshfs-gtk -o sshfs-gtk `pkg-config --cflags --libs gtk+-2.0`
*/
#include <gtk/gtk.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <wchar.h>
static void destroy( GtkWidget *widget, gpointer data ) {
[Code] .....
I've been creating an API and I'm now stuck on callbacks. There are many APIs that allow callbacks to class members(e.g. Windows API) using a void pointer to the object. I've searched the internet for hours and I can't find one example of how to use the "hidden object parameter" of an class method pointer that doesn't use std::function/bind or boost::function/bind. Any information on how API's like Windows API are able to use class methods as callbacks
View 6 Replies View RelatedI've been having a problem concerning the initialization of const static integral members with floating point calculations. I'll let his sample program do the explaining:
class Foo {
public :
Foo() {}
const static int samplerate = 44100;
const static unsigned short tempo = 120;
[Code].....
I know you can't initialize const static non-integral types on the same line on which they're declared, but I don't see why even an implicit cast to an integral type should be disallowed. I make my calculations using doubles, so I'm surprised that even though it should degenerate into an integer - it's still a problem for the compiler.
The reason that class members are private by default is because, in general, an object of a class should be a self-contained entity such that the data that make the object what it is should be encapsulated and only changed under controlled circumstances. Public data members should be very much the exception. As you’ll see a little later in the chapter, though, it’s also possible to place other restrictions on the accessibility of members of a class.
View 17 Replies View RelatedIf I have a struct of some vector members, like
struct {
vector<double> a;
vector<double> b;
vector<double> c;
// ...... continue
} struct_test
How can I assign a value (push_back()) to all the vector members simultaneously, instead of do it one by one?
Suppose I have a class "A", which has a method "void AMP_call()" that calls paralel_for_each in which another method, "float amp_function(float) restrict(amp)". When I call that method, can it then use members of "A"?
class A {
void AMP_call();
float amp_function(float) restrict(amp); // do something on a device
float allowed_variable;
std::vector<bool> not_allowed;
[Code] ....
Another way to frame my question, perhaps to make it easier to understand what I am after, would be that I want to know what happens if an amp-restricted method is called where the body of the class itself (which is not amp-compatible and afaik doesn't have to be since it's not passed to the device) may contain members that are not amp-compatible.
All of the msdn blogs I could find deal with which functions and methods can be called from within a parallel_for_each loop, but not with which variables are available to the lambda function itself.
Need a C++ constructor to initialize each members of an array. how to give value for for each elements of an array declared as a class object according to the users input.
View 1 Replies View RelatedWrite a C++ program to implement the following description:
1. Define a global structure and name it GStruct with the following members:
a. X as integer
b. Y as integer.
2. Define a local structure inside the main and name it LStruct with the following members:
a. X as integer
b. Y[3] as GStruct
3. Inside the main declare two variables V1 and V2 of type LStruct.
4. Give values to all of their members by using input statement (cin).
5. If V1 equal V2 print "They are equal" else print "Not Equal".
#include <iostream>
using namespace std;
struct GStruct {
int x;
int y;
};
int main() {
[Code] .....
It's hard to give a precise title but here is the question in detail: I have a class, something like this:
Code:
class classA{
public:
void fnA();
...
};
and another class that contains objects of classA:
Code:
class classB{
public:
classA A1;
classA A2;
classA A3;
vector<classA*> vA;
...
};
classB B1;
Now is it possible to access B1.vA from B1.A1.fnA() through some kind of pointer chain like this->parent->vA ? If so
How does an object access its private data members in copy constructor.
The relevant part of the code: Code: C::C(const C &obj)
{
x = obj.x;
y = obj.y;
}
Normally the object1 called "obj" cannot access its private data members outside. But in this situation it can access. How can it be explained?
Here are the complete code:
Code:
#include <iostream>
using namespace std;
class C{
public:
C(int,int);
C(const C &);
[Code] .....
Let's say I have the following class:
class MyClass {
private:
int m_myInt;
public:
int myInt() {return this->m_myInt;};
int myFunc();
};
Which of the following is to prefer;
int MyClass::myFunc() {
return 2*this->m_myInt;
}
or
int MyClass::myFunc() {
return 2*this->myInt();
}
The second one seems better? Are both OK? What's the best practice?
i have seen many c++ programs, where the private members from a header file are accessed in the source file. why is happening? As to my knowledge a private member cannot be accessed until it is friend function or member.
View 2 Replies View RelatedI have a little problem with template classes and their specialization. Here is a short example:
template <typename T>
struct A{
// some typedefs
[Code]....
The above example is not compiling, because of the assignment of the const static double. Double needs a constructor, but that doesn't work (or seems not to work) with static.
I'm not sure, if it works at all in C++ that way. All I want is a template struct with some typedefs and a constant which is different for different specializations. Don't think it has to be static, but that would be better style, wouldn't it?
I've been reading the tutorials on Friendship and Inheritance [URL] ..... but I still don't understand why I can't access members of the same struct type.
bool wordBeginsAt (int pos) {
if (pos == 0)
return true;
///use the 'message' string
Message go;
return isAlphanumeric(go.messageText[pos]) && (!isAlphanumeric(go.messageText[pos-1]));
}
The code above is located in a source file, where the function isAlphanumeric passes a char value, and Message is the struct containing the string I want to access. Below is the declaration of the struct and string located in the corresponding header file.
struct Message{
.
.
.
private:
std::string messageText;
};
My frustration comes when I try to call and assign messageText like the tutorial does to its private members, but I keep getting an error saying I can't access the string because it is a private member. Is there a way to access the string without having to pass it through the function wordBeginsAt?
I am doing C++ data structures exercises, and I am still learning some of the more basic concepts. I have a parent class:
template<class T>
class linkedListType {
public:
protected:
int count;
nodeType<T> *first;
nodeType<T> *last;
private:
};
Derived class:
#include "linkedListType.h"
template<class T>
class orderedLinkedList: public linkedListType<T> {
public:
void mergeList(orderedLinkedList<T> &list1, orderedLinkedList<t> &list2) {
first = list1.first;
...
} private:
};
There is more code in my mergeList() function, but I included the line that is giving me problems. The error that my CodeBlocks compiler is giving me is that 'first' was not declared in this scope.
Strangely enough, if I change it to this->first, the error disappears.
1. Why does it not recognise 'first'?
2. Why would this->first work at all? Is the 'this' object a smart pointer?
I am trying to use 'this' pointer but i am confused why 'this' pointer is not available for static member functions.
Code:
#include <iostream>
#include <fstream>
#include <stdlib.h>
using namespace std;
const int MAX = 20;
const int MAXPTR = 100;
class name {
private :
char fname[MAX], mname[MAX], lname[MAX];
[code].....
I am using GNU GCC Compiler via Code::Block
Error : 'this' is unavailable for static member functions
Code:
class NavMeshLoader {
public:
NavMeshLoader() {
m_navMesh = loadAll("all_tiles_navmesh.bin");
m_navQuery->init(m_navMesh, 2048);
[code]....
Code:
template <size_t s>
class foo {
public:
foo()
{
}
template <size_t l, size_t r>
[Code] .....
The above doesn't want to compile.
error C2995: 'foo<l+r> operator *(const foo<s> &,const foo<r> &)' : function template has already been defined
see declaration of 'operator *'
see reference to class template instantiation 'foo<s>' being compiled
with
[
s=4
]
If I change the operator to return a foo<s> it does compile (but that's not the behaviour I need).
if I move the operator to outside the class (removing the 'friend') it does compile and behaves how I need, but I can't access non-public members so I can't write the implementation correctly.
I have code working, but that is largely because a vector that I am using as part of a structure that is the first of two elements of a MAP (with the second being an integer that is assigned later) is serving in its original, purely vector form, to fill out a set of selections on a DOS screen (option 1, 2, 3, etc.).
I do use the MAP, because it is a simple means of referencing the integer value using a word that is part of the structure, and is probably appropriate, saving me a search through the vector of words and calling up the value at the same location in the vector of words in a vector of corresponding numerical values. I DO feel that what I'm doing to produce the selection list is something of a "cheat" because I do not know how to access the same data within the structure component of the MAP by simply using a similar numerical reference (e.g. "MAP[1].structure.word", or would that be "MAP.structure.word[1]" ????) to print out the words in the structure in the map as choices on the screen.
I don't want to change or expand the contents of the map, just access and print each one in a simple loop with a number from the loop counter to the left of each word.