C++ :: Does Polymorphism Affects Operators Overloading?
Nov 24, 2013
I must overload [] but at the same time I must use polymorphism. I wonder if using polymorphism affects operators overloading since when I modified the first class by writing "virtual":
I have two class GameOfLife and Cell and i want to overload square braket for class GameOfLife."if g is a GameOfLife object, g[10][5] will return the Cell at row 10 and column 5. If there is no such Cells, then it will return a new Cell with position (-1000,- 1000)."
but if g[10][1000] and 1000>cols,then it returns different Cell exp (3,2) How i do control the col ( [row][col] )?
I have a small piece of code that used the set::insert function on a set of myClass. For that, I need to overload the < and > operators, which I have, but I still get a huge error saying it can't compare.
set<MyClass> mySet; MyClass myClass
All the class information gets filled in. Then, I try to insert... mySet.insert(myClass);
bool operator<(MyClass &lhs, MyClass &rhs) { return lhs.name < rhs.name; //name is a string }
The error says ...stl_function.h:230:22: error: no match for 'operator<' in '__x < __y' MyFile.h:80:6: note: candidate is bool operator<(MyClass&, MyClass&)
I made a program that allows the user to enter information of credit cards on an array of size 5, however I need to allow the user to compare the five credit cards with each other and I am having problems with this particular part. I made my bool operator functions for the operator< and the operator> but how to make the user be able to select which cards he wants to compare and how to compare them. My code is the following:
#include <iostream> #include <fstream> #include <string> using namespace std; const int SIZE = 5; enum OPCIONES {CARGAR=1, ABONAR, NADA};
S I want to have different >> operators for several derived classes. Has I tested...
Code: class base{ friend std::istream & operator>>(std::istream & in, base & v); public: base();
[Code]......
I noticed that the base operator is the only one being called for all 3 objects. which makes sense and now that I think about it I am more surprised that the "derived operators" compiled at all.
Still, how would I go about declaring different overloaded operators for the different classes?
I am stucked in a problem of overloading arithmetic operators such as "+,*" for a class in the form
class Point { int N; // dimension of the point double *Pos; // length of N }
My assign operator is : Point& Point::operator= (const Point& pt) { N= pt.N; if(Pos == NULL) Pos = new double[N]; memcpy(Pos, pt.Pos, N*sizeof(double));
[Code] ....
The add operator "+" is: Point operator+( const Point& pt1, const Point& pt2 ) { Point ptr = Point(pt); // this is a constructor for (int i=0; i<pt1.N; i++) ptr.Pos[i] += pt2.Pos[i]; return ptr; }
Based on the above overloading, What I am going to do is :
P = alpha*P1 + beta*P2; // alpha and beta are double constants, P1 and P2 are Points objes
It is ok with Intel C++ 14.0 compiler, but does not work with the microsoft visual c++ 2012 compiler in debug mode in visual studio 2012.
I stepped in those operators and found that visual c++ compiler deconstructs the ptr in operators "*" and "+" before its return while intel c++ finished the operation P = alpha*P1 + beta*P2; and delete those ptrs at last.
Portability of my operator overloading is worse. How to get those arithmetic operators overloading for class with pointers in it.
class Base { ..... ..... ..... virtual void display();
[code]....
in the above polymorphism why is it called runtime polymorphism when i can say seeing the code itself that display() function in derived gets executed with ptr->display(),so how does it become runtime polymorphism when i could get decide at compile itself ???
How can we calculate tax of vehicle with polymorphism? There are 3 types of vehicles: long, commercial, and private vehicles' classes. There is a common class about all vehicles.
BASE class: 1.Brand and series name (such as Toyota Corrolla, Isuzu etc.) 2.Year of production (you can term it model) 3.Engine size in dm3 4.Owner’s name (including surname) and identity 5.Plate number.
COMMERCİAL : 1.Number of seats (apart from the driver) 2.Data to indicate whether the commercial vehicle is allowed to operate at night.
LONG : 1.The tonnage (max load in tons) 2.Data to indicate whether the long vehicle is allowed to carry goods internationally.
PRİVATE: 1.The class label which can be one of {A,B,C} .
I have been reading up about object oriented programming recently and have come across 'Encapsulation, Polymorphism and Inheritance' as i understand it so far all OOP programs should use these three concepts. So i started thinking how do i get these concepts into my program as i am using WPF C# and i could not really find much good info about how these concepts apply to WPF programs.
Or do these concepts just not work with WPF programs?
I have couple of objects which are using some amount of methods. Right now my application is not OOP and i am going to transfer it to OOP. So i would create each class for my each object. Almost all methods are in use for each object, the only one thing which is changing some of those objects passing not all parameters inside specific method. I can go two ways one is prepare interface for all methods i got and each of my classes could implement its own definition for it but other way almost all would implement exactly the same methods but with different parameters so maybe its better to create base class then for each object do inheritance from base class (polymorphism). inside base class i can prepare base methods and classes which will inherit from that class would override those methods for requirements they want.
So imagine: You got:
Memory CPU Latency
and all of them using mostly all of those same methods (only arguments for one of them could be use different way):
Base class: Stuff prop: name, id, date ... methods to ovveride: ExecuteQuery(), ExportToExcel() ...
classes: CPU, Memory, Latency (inheriting from Stuff) ovveride methods and align its definition for specific class use (remember mostly only passing args are used or not by specific class)
The most important thing is that those every objects mostly using all of those methods and what is diffrence that one object can use all of available parameters inside this method and other one no. What i should do? Go with interface or inheritance and polymporfizm inside base class?
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?
Having issues with program to create a shape area calculator with circle square and rectangle. the uml goes as follows:
Where the UML has shape as the abstract class with public area():double, getName():string,and getDimensions:string, rectangle derived from shape with protected height, and width, and a public rectangle(h:double, w:double), followed by a derived square from rectangle with just a public square(h:double), and finally a circle derived from shape with a private radius, and a public circle(r:double).
[URL]
Have linked my program and it is giving me the following compiler errors:
error: 'qdebug' was not declared in this scope line 15 of main
error: cannot declare variable 'shp' to be of abstract type 'shape' line 22 of main
error: expected primary-expression before ')' token lines 29 -31 of main
(note previously had qstring as a header file yet changed to string since I was getting error qstring was not declared in this scope.)
I've been working on this project which inserts data for different types of books lately, and I'm trying to utilize inheritance and polymorphism. The issue I've been having is after I create an object with my MediaFactory, I go to insert data into that type of object, but it won't reach the correct child class. The parent class in this case is MediaData. The class I'm trying to reach is Childrens, and the class that falls in between is called Book. The function I'm calling to insert the information is setData(ifstream&). This function simply places the information from a txt file into an object with the insertion operator.
Right now the program runs into the setData function of Book instead of Childrens. I need Childrens so I can enter all the required attributes (title,author,year). The call to this function is in MediaManager through the function called buildMedia, and my test is running into the case if (type == 'Y'). From there a pointer of type MediaData is created and pointed to a new object returned of type Childrens. I'm using my debugger in Xcode which does show that the correct object type (Childrens) was created.
I've tried a couple things so far. First I created another function called getData. From there I passed in *media and infile (txt input file) into that function, which then passed it right into setData with a pointer to the object and infile in the parameter. That didn't work, so I also tried going back into Childrens and removing MediaData from all my virtual functions and replacing it with Book. I got the same result when that happened; It morphed into Book class instead.
I have a portion of my UML as a reference. Childrens is a Book; Book is a MediaData. I also included all code for MediaManager, MediaHash, MediaFactory, MediaData, Book, and Childrens.
I did not include the operator overloads in the .cpp files to eliminate some redundancy.
//----------------------------------------------------------------------------- // MediaManager.h // Manager class for MediaData type objects //-----------------------------------------------------------------------------
#ifndef MediaManager_H #define MediaManager_H #include "MediaHash.h" #include "MediaFactory.h" #include "MediaData.h" using namespace std; class MediaManager {
Below code produces run-time segmentation fault (core dumped) when execution reached line 53: delete [] array
Code 1:
#include <cstdlib> #include <iostream> using namespace std; #define QUANTITY 5 class Parent { protected: int ID;
[Code] ....
Output of code 1:
Constructor of A: Instance created with ID=1804289383 Constructor of A: Instance created with ID=846930886 Constructor of A: Instance created with ID=1681692777 Constructor of A: Instance created with ID=1714636915 Constructor of A: Instance created with ID=1957747793 A::showID() -- ID is 1804289383 A::showID() -- ID is 846930886 A::showID() -- ID is 1681692777 A::showID() -- ID is 1714636915 A::showID() -- ID is 1957747793 Try to delete [] array.. Segmentation fault (core dumped)
Question: Why does segmentation fault happen in code 1 above?
I am making a very basic parent/child class based program that shows polymorphism. It does not compile due to a few syntax errors reading "function call missing argument list. Lines 76 and 77, 81 and 82, and 86 and 87.
#include<iostream> using namespace std; class people { public: virtual void height(double h) = 0; virtual void weight(double w) = 0;
#include<stdio.h> main() { int i=4,j=7; j=j||(printf("you can")&&(i=5)); printf("%d %d",i,j); }
output: 4 1
Although I am specifying the braces for the && operator so that it gets executed first..Then also the value of i remains 4 only..Why does not it gets changed to 5??Also the printf does not execute??
Switch case statements are a substitute for long if statements that compare a variable to several "integral" values ("integral" values are simply values that can be expressed as an integer, such as the value of a char).
So does that mean switch statements can only test if variable == value and nothing more, like > < >= <= != etc... ? I tried to make a program to test this and it seems like switch statements are limited to == but I'm not sure, maybe I'm doing something wrong.
This is the program I tried to make to test this:
Code: #include <stdio.h> int main () { int n;
[Code]....
So is it true that switch statements only work with the built in == operator? if that was the case then I would feel rather meh about switch statements.
I'm experimenting with a custom memory-pool for my application, and I initially planned to override the global new and delete operators to allocate memory in this pool. But since I'm using QT, this will apply to all the QT-related stuff as well. Should I instead just override the new and delete operators per class?
