I want to overload pure virtual function from 3rd party SDK class to put my debug messages like that:
errorStatus aXsaction(){printf(_T("
abort transaction"));transactionManager->abortTransaction();}
#define transactionManager->abortTransaction() aXsaction()
But compiler complains on the minus sign:
error C2008: '-' : unexpected in macro definition
Is it possible to trick the compiler?
I defined a virtual class and three other classes based on it. I want to use them like this:
int main() {
Dirichlet_t D;
Neumann_t N;
Cauchy_t C;
PDEBoundary_t * B1=& D;
PDEBoundary_t * B2=& N;
PDEBoundary_t * B3=& C;
[Code] .....
but I got two major errors
1: "object f abstract type is not allowed" error.-----why not?
2: "the derived class must implement the inherited pure virtual method"-----Did't I?
I wrote the following program, it can be compiled and run, but there is warning saying that if virtual function is defined, there should be a destructor. How to do that I tried many different ways I can thought of, but none of them works.
#include <iostream>
using namespace std;
class cell_c {
public:
double p;
cell_c() {p=1;}
virtual void print() {cout<<p<<endl;}
[code]....
I am trying to bend my head around polymorphism but I can't figure out how to use the virtual method properly. I have the following superclass:
Code: class comparable
{
public:
comparable();
virtual bool compare(comparable &other)=0;
}; and the subclass:
Code: class score : public comparable
{
public:
score(string player,int highscore);
bool compare(comparable &other);
string name;
int highscore;
};
My problem is that I do not know how to define the virtual function compare in the subclass score:
Code: bool score::compare(comparable &other){
if(this->highscore > other.???){
...
}
}
How do I tell the compiler that the type is of score?
class Parent{
public:
virtual int width();
virtual int height();
int area(){return width()*height();};
[Code] ....
I am a beginner, got confused about:
template<typename T> int compare(T &a,T &b);
int compare(const char *a,const char *b);
char ch_arr1[6]="world",ch_arr2[6]="hello";
compare(ch_arr1,ch_arr2);
After running the code above,we got to know the non-template function is called. What I know is that the array arguments ch_arr1,ch_arr2 will not be converted to char * because the parameters are references in the template functions.
ch_arr1,ch_arr2 need to be converted to const char * if compare(const char *a,const char *b) were called.
I just wanna know what exactly happened behind that? and why?
I want to be able to do
someFunction(MyObject)
rather than
someFunction(MyObject.getWhatIWant())
I know I can do &MyObject, MyObject() and MyObject[0] by overloading operators but is it possible with just plain old MyObject?
this is assuming that I have no access to someFunction(), i.e, it cannot be modified.
Firstly, is it legal to overload a template function in a class? This is what I did
class FILE_txt
{
public:
FILE_txt(const char* );
[Code]....
Say I have a class that requires dynamic allocation to implement a few of the operators. Take "+" for example; I need to create a new object to hold the sum of the two parameters whose size is not known at compile time.
I'm pretty sure the standard way to indicate a failure inside the overloading function would be to throw an exception. However I am currently involved in an embedded(ish) project where the spec. says no exceptions are to be used.
I think I have 2 options:
1. Return an "invalid" object (with a flag indicating an error has occurred) and check for this after each operation.
a = b + c
if (a.err)
// handle error
or
2. To forsake operator overloading entirely and think up a new way of doing things where all functions that involve dynamic allocation can return error codes. but this seems rather terrible too as I may end up with something like:
objA a
if (add(&a, b, c) == -1) // assuming b and c are initialized before this snippet starts
// handle error
Is there a number 3 that I haven't thought of? It seems that not allowing exceptions is fairly common even in the non-embedded world [URL] so how is this normally done? or is operator overloading usually avoided when exceptions are not allowed?
I want to overload prefix and postfix increment(++) operators with friend function. I also have to use the constructors for this. How can I do this? in C++
View 4 Replies View RelatedConsider the class specification below. Write the prototype (i.e. header) of a member function to overload the insertion operator (i.e. <<). The << operator is to output the data members of an instance of class StudentTestScores into an output stream. Your definition should allow for chaining of output operations (e.g. cout << x << y; where x and y are of type StduentTestScires).
#include <string>
using namespace std;
class StudentTestScores{
private:
string studentName;
float *testScores; // used to point to an array of test scores
int numTestScores; // number of test scores
[code]....
I'm having some issues with my code. For the produce function i am getting an error saying 'no instance of overload function produce() matches the argument list' and also for the lines buffer[head].data = message; buffer[head].time = current_time i get an error saying 'expression must have pointer to object type.
In the code i'm not sure if i passed the variables to the function correctly. I have attached the code .....
code produce.txt
have a look-
class Base
{
private:
{
[Code].....
my question is why we can't directly call the member function of the desired class instead of using virtual function.
***********same program using virtual keyword*******************
class Base
{
private:
{
[Code].....
Why we generally prefer the 2nd one i.e with virtual keyword. why we can't directly call the member function of the desired class instead of using virtual function...make me understand this point..
What I'm trying to do :
struct foo {int x; int y;};
foo function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}
Works as is, however when I try doing it through seperate class files :
//header file for class example_class
struct foo {int x; int y;};
foo function_example(int x, int y);
//source file for example_class
foo example_class::function_example(int x, int y) {
foo temp;
temp.x = x;
temp.y = y;
return temp;
}
I get an error telling me that foo is undefined, and that declaration of function_example(int x, int y) is incompatible with the declaration of it in the header file.
I have this header file called Shape.h containing these function declarations. and a Shape.cpp which contains the body of the function. I am not showing it since it is not needed.
//This is from Shapes.h header file
#ifndef SHAPES_H
#define SHAPES_H
#include <iostream>
[Code]....
I have this unfinished Main.cpp because the third line "JuanSanchez::Circle *pCar = new Circle; " is giving me a compiler error "error C2061: syntax error : identifier 'Circle' "
#include "Shapes.h"
int main()
{
const int arrayIndex = 4;
JuanSanchez::Shape *myShape[arrayIndex];
JuanSanchez::Circle *pCar = new Circle;
}
What Could be causing this error?
I have a function, int teleport_to_game(int,float,float); in my class. My question is should I change the int to define a function to a different type?
View 2 Replies View RelatedI'm currently making a game and what happens is that during runtime, it suddenly closes and a message is shown in the console saying "Pure virtual function called at runtime".
Here is the code: [URL]
The problem seems to occur somewhere between lines 662 - 695. And it seems to only happen when the size of the vector reaches 1.
Instead of this:
#include <iostream>
struct Object {
int size; // Want to avoid this because size is (almost always) constant
Object (int s): size(s) {} // for every Object subtype.
[Code] ....
I want this:
#include <iostream>
struct Object {
virtual int getSize() const = 0;
};
struct Block: Object {
int getSize() const {return 5;} // always 5, except once in a blue moon it may change
[Code] ....
The Decorator Pattern works (getSize() can then return 6) but it is a poor choice for my program because it will cause more problems (due to many containers holding its old address, among other things. Any way to achieve this without any change of address, and without creating new storage somewhere, either inside the class or outside the class (too much responsibility to follow that stored value for the rest of the program just for this rare change, and creating a data member uses up too much memory for the many, many Block instances)?
Let's look at this simplified code, it gives compilation error
#include <iostream>
using namespace std;
class A {
public:
void showInfo() { cout << " This is an instance of A" << endl; }
[Code] ....
Without using pointer, how to make this works?
I have found that when I dump a C++ object from memory to a file - it seems that there is a misplacement of the last Virtual-Function-Table pointer - in that appears at the beginning. The result is that the gdump information based on this object dump (using green hills) is incorrect. I copied the contents of the gdump information below. The executable is compiled in linux.
Basically MEIO::CameraStatus contains an item that relates to its parent class (line 188). Then it has 18 items that are all Diagnostics::EventsCounter items. Now for each Diagnostics::EventsCounter item there is a Virtual-Function-Table Info Pointer as its last item. All is fine and good except that the last item of MEIO::CameraStatus which is _selfReset is missing its last item of 4 bytes (which is the Virtual-Function-Table Info Pointer ). On the other hand - right before the first Diagnostics::EventsCounter item ("_vidErrors") - there is an extra 4 bytes which happens to be the Virtual-Function-Table Info Pointer. As I said the gdump information file does not see this.
Why the object memory "moves" the last Virtual-Function-Table Info Pointer to the beginning (right before _vidErrors) and is there a way to "fix" this?
///////////////////////////////////////////////////////////////////////////
"MEIO::CameraStatus" val:0x000002f0 ind208,-1) Struct-Begin Info
188: "" offset 0, Parent-Class Private Info C++ Struct ref = 114
189: "_vidErrors" offset 160, Member Info C++ Struct ref = 128
190: "_vdiErrors" offset 480, Member Info C++ Struct ref = 128
[Code] .....
I'm writing a class "Property" for a program that manages different types of properties. This is my .h for y base class. I was trying to write a virtual void function to convert different children classes to strings that can be displayed, but Xcode is freaking out.
I had it as:
virtual void toString()= 0;
and it gave me an error message: "Virtual can only exist in non-static member functions" and "field has incomplete type 'void'"
I changed it to:
virtual string toString() = 0;
and the error message didn't change.
Is this an issue with Xcode or did I do something wrong? Even after changing it to string it told me that it "has incomplete type 'void'"....
Here's my question. I'm coding a basic Linked List class (for the purpose of understanding and having fun, I know about STL), LList.
I have overloaded the [] operator so it returns the data of the index-th node in the list, for example, if I code
LList x;
....
cout<<x[5];
it prints the data of the 5th node in the list (for fun I decided to index from 1 to infinity).
My question: Now I want to be able to assign the value to the index-th node data, using [] and =, for example, I want to be able to write:
LList x;
.....
x[5] = 121;
How can I do that?
How would i be able to overload a multiplication operator that if, in the main example(0, 5, 0) * example (0, 5, 0) is given, it gives me 25?
View 1 Replies View RelatedIs it possible to overload a variable in a derived class? Example:
struct Circle
{
int radius() const { return r; }
private:
int r;
}
struct Smiley : Circle
{
// inherits the function int radius() const, but doesn't return Smiley::r
private:
int r;
}
I'm still pretty new to classes so what am i doing in this code that is wrong.
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <string>
using namespace std;
class BunnyInfo{
[Code]...
I'm trying to learn how to use variadic templates, and I decided a great example would be serializing a series of types into a stringstream:
Code:
// Send a fully constructed message.
virtual void send(ostringstream &msg) = 0;
// Construct a message from the arguments and send it.
// This is the usual entry point.
template <typename ...Args>
void send(Args ...args {
[Code] ....
This works fine, so far as I can tell. However, I decided to see if I could specialize the way certain types are serialized. I tried using a Google Protocol Buffer object as an example, and added this:
Code:
// Handle a protocol buffer type while constructing a message.
template <typename ...Args>
void send(ostringstream &msg,
const google::protobuf::MessageLite &protobuf, Args ...args) {
std::string msg_str = protobuf.SerializeAsString();
msg << msg_str;
send(msg,args...);
}
I would expect this overload to be preferred over the generic T overload when a protobuf object (which always inherits from MessageLite) is passed into send() anywhere in the list. However, this is not happening. I am getting an error message to the effect that << doesn't know how to deal with my concrete type, pointing at the T overload.