C/C++ :: Appointment Scheduling Program - Why Are Destructors Being Called
Mar 5, 2015
I am in a intro C++ class and have an assignment to create a patient appointment scheduling program. I finished my code, but when I run it the destructors in each class are being called a bunch of times and the menu shows up at the bottom of the that, so the whole output looks like a mess. Identifying why the destructors are being called like this?
"Destructors for a derived class object are called in the reverse order of the constructors for the object. This is a general rule that always applies. Constructors are invoked starting with the base class constructor and then the derived class constructor, whereas the destructor for the derived class is called first when an object is destroyed, followed by the base class destructor."
But why, or is it just because, so programmers know which one and modify their destructor accordingly??
#pragma once #include <iostream> class CBox // Derived class { public: // Constructor explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}
[Code] .....
Before the program ends, at return 0;
I would expect the CBox destructor to be called 3 times but it is being called 6 times? Why? Also in this code:
#pragma once #include <iostream> class CBox // Derived class { public: // Constructor explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}
[Code] .....
Why is the destructor called 3 times? When have you really destroyed a CBox? Doesnt emplace only create it and store it, then thats it?
[URL] .....
For pushback:
void push_back(value_type&& _Val) {// insert by moving into element at end if (_Inside(_STD addressof(_Val))) {// push back an element size_type _Idx = _STD addressof(_Val) - this->_Myfirst;
I am an IT college student and this is a self-assigned project i have done in an attempt to learn programming in C AND at the same time how time scheduling of an OS works (Both done in order to prepare for upcoming semester exams) using FCFS ,SJF, RR and PS algorithms (planning on adding SRT too sometime soon). (took me 9 hours total work time including validations). What i wanna know is from more seasoned coders if i am on the right track. *cross fingers*
I've recently completed a fully functional round robin algorithm for a class, however upon running a myriad of test cases I found where mine fails. I think it best to show with an example:
Currently what happens is this, it runs perfectly from process 1 through process 3. However once it reaches process 4 it does the appropriate thing and adjusts my total processing time (q variable) to the arrival time of process 4. Great! But then, it rolls over to check the queue again and it's bringing in process 5, changing q to it's arrival time. Then it proceeds to swap them in and out due to them both now being in the queue and time quantums/slices running out.
My question is this: How/where do I put a lock on the while loop that runs the simulated scheduler (round robin in this instance) to not grab the next process when there's a time gap in between each process.
This specifically is the two lines that I can't seem to get working as they should:
if(arrival[i]>q) q=arrival[i];
FULL CODE BELOW
#include <iostream> using namespace std; void RR(int n, int burst[], int arrival[], int throughput) {
class Base { public: virtual ~Base() { cout << "Calling ~Base()" << endl;
[Code]...
Now this program produces the following result:
Calling ~Derived() Calling ~Base()
i was reading online and got stuck here. i am unable to understand why 'calling ~Base()' is been printed here? when we reached delete pbase; in int main() it goes to Base class first and finds that its destructor is virtual so it goes to Derive class and finds another destructor and executes it but why does it prints ~Base() in any case?
My programs complies and runs. However, whenever i try to enter something when prompt to enter the number of accounts i wanted to create my program crashes.
By the way, im using codeblocks.
it says
terminated called after throwing an instance of 'std:: out of range'. what(): basic_string::substr"
Code: #include <iostream> #include "clsInterest.h" #include "clsDate.h" using namespace std;
Write a program with two functions both called from main(). The first function just prints "Hello". In the second function ask the user to enter a number. Calculate the square root of the number and return the result to main(). In main() print the square root value.
Every time we pass an object to a function, and when the function ends and the object is not necessary anymore the destructor is called. if it's passing by value then a copy of the object is passed. if the object has a pointer inside of it so we implement the copy constructor to create a new pointed-variable so the original pointer will not get deleted.
so far so good. But what about passing an object to a non-member function by reference?
The language says that as soon as the function ends - the object will be deleted , because we passed by ref. that means that after the function ends - the object is not usable anymore! =What does that say? that in c++ you can't pass object by ref. because it will get deleted and un-uasable??
Varifying it with a compiler shows that the object is NOT deleted after the function ends.
My program seems to be working fine, except for when I call on my delete function. I don't receive any errors, but when I call the delete function my program outputs nothing and freezes. As in, my print function (which is called before the delete function) doesn't even work. I've tried removing bits of the function to see if I could pinpoint where exactly the issue is, but I've had no luck.
#include <iostream> #include <string> using namespace std; class List{ private: struct node{ string _data;
[Code] ....
And the function that is causing me trouble:
void deleteNode(string data){ node* del = NULL; t = h; n = h; while(n != NULL && n->_data != data){
I am working on this project where I need a function to be called every second. At this time, I am thinking that I have to create a thread but I am clueless on how it will get called every second.
The following are the cases when copy constructor is called.
1)When instantiating one object and initializing it with values from another object. 2)When passing an object by value. 3)When an object is returned from a function by value.
I don't understand #2 How can and object be passed by value? when I think of passing object I think of passing by address or reference. explain
I don't understand #3 how can a function returned object by value I think of again passing by address or reference.
The copy constructor is called twice, once when you pass an object by value, and once when the object is returned from a function by value. But why is the destructor being called twice?
I was wondering that why in the below code, the copy constructor is called 2 times.
Code: class A { private: static int count; int age; public: A()
[code].....
I think that when f(a) is called, since I am passing this as value, no copy constructor should be called. The copy constructor should called when the return object "x" is assigned to:
When the below is done, does it call the constroctor only, and if yes, constructors do not have return types so how does it work? is there anything behind the scene?
wxAddHandler(new wxPNG_HANDLER); and sf::RenderWindow(sf::VideoMode(...),...);
I can't get my 'Front End' view model's constructor to be called. If i remove my dependency from the mvvm-light framework and use MSDN mvvm paterns then the constructor is called. What am i doing wrong. It seem like there is a data context binding issue between my XMAL and my view model backing.
ViewModelLocator.cs using GalaSoft.MvvmLight.Ioc; using Microsoft.Practices.ServiceLocation; using Point_Of_Sale.Model; using System.Collections.Generic; namespace Point_Of_Sale.ViewModel { public class ViewModelLocator
I do not have a copy constructor, i just want to use the shallow copy. Why i get Debug Assertion Failed error? If i delete the destructor, all work fine.
I get it, the problem occurs when the material from j1 is deleted right? Because it has already been delete by j2.
I am trying to use myfile to create and write user data to a file [URL].
At the moment I only want to save as .txt so that I can open it to see that it wrote to file properly.
The main issue I get is that it says the file is not open when my program gets to the error checking at the very end, a few guides mentioned that if the file was not yet created a file with the specified name would be generated in the same folder as main on the hard drive. I did try creating the file as a notepad .txt file but it still read the error. Here is the snippet concerning the writing of the file:
it compiles fine with the rest of the program and everything runs smoothly, it just isn't writing to a file.I have included <string>, <iostream> and <fstream>.
#include<iostream> using namespace std; class Cents { public: int m_nCents; Cents(int nCents=0):m_nCents(nCents){ cout<<"Calling normal constructor with value:"; m_nCents = nCents; cout<<m_nCents<<endl;
[code].....
Question is :Why is the overloaded copy constructor that I have written not getting called here?Internally default copy constructor is getting called.Thats why we get value of obj2.m_nCents as 37.
Although MyThread1 and MyThread2 using critical section to protect the shared data m_Data, I will still suspend MyThread1 before accessing the shared data, to prevent any possible conflicts.
The problem is:
(1)When the first invoke of MyFun2, everything is OK, and the return value of MyFun2(that is nResult2) is 1 , which is expected.
(2)When the second, third and fourth invoke of MyFun2, the operations in MyFun2 are executed successfully, but the return value of MyFun2(that is nResult2) is a random value instead of the expected value 1. I try to using Debug to trace into MyFun2, and confirm that the last return statement is just return a value of 1, but the invoker will receive a random value instead of 1 when inspecting nResult2.
(3)After the fourth invoke of MyFun2 and return back to the next statement follow MyFun2, I will always get a "buffer overrun detected" error, whatever the next statement is.
I think this looks like a stack corruption, so try to make some tests:
1.I confirm the /GS (Stack security check) feature in the compiler is ON.
2.If MyFun2 is invoked after MyFun1 in MyThread1 is completed, then everything will be OK.
3.In debug mode, the codeline in MyFun2 that reads the shared data m_Data will not cause any errors or exceptions. Neither will the codeline in MyFun1 that writes the shared Data.
