C++ :: Add Constant Object To Linked List Of Objects
Feb 10, 2014
I have a standard linked list in template format (with T being the typename) with the following relevant insertion operators:
bool PushFront (const T& t); // Insert t at front of list
bool PushBack (const T& t); // Insert t at back of list
I want to build a list of pointers to objects (we'll call them objects of class Box for simplicity) that is member data for a parent class (we'll call that class Warehouse). However, I want to have a constant Box....const Box INVISIBLE_BOX = Box(); that represents a nonexistent Box. However, I cannot use either
PushFront(&INVISIBLE_BOX)
or
PushBack(&INVISIBLE_BOX)
to add INVISIBLE_BOX to the list of boxes without getting an invalid conversion error invalid conversion from âconst warehouse::Box*â to âwarehouse:: Box*â [-fpermissive]
What can I do to make it take a constant Box? I am using g++ to compile these files.
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May 18, 2014
Main
#include <iostream>
#include "item.h"
#include "inventory.h"
#include <stdlib.h>
#include <string.h>
#pragma GCC diagnostic ignored "-Wwrite-strings"
[code]....
what I would want to happen is is have my item increment in size/count instead of a new object. How would you handle this algorithmically.
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Apr 19, 2013
I have a list of objects that I need to read information from each object to compare to a user input prompt.
#include "Passenger.h"
#include "Reservation.h"
#include "Aircraft.h"
#include <iostream>
#include <fstream>
#include <string>
#include <list>
using namespace std;
//Function Prototypes
void flightRoster(list<Reservation>&);
[Code] ....
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Apr 14, 2014
I'm having a problem trying to modify my patient's data. It seems to work, but once the block of code ends it does not save to the linked list.
Problem located in case M.
linked list template header: [URL] ...
patient header: [URL] ...
patient implementation: [URL] ...
#include <iostream>
#include "listTemplate.h"
#include "PatientRecord.h"
using namespace std;
char menu() {
char input
[Code]...
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May 16, 2013
Error:
--------------------Configuration: nc - Win32 Debug--------------------
Compiling...
cv.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/nc.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
nc.exe - 2 error(s), 0 warning(s)
Compiles with 0 error but on running 2 Errors appear.
I'm Inputting data of an object from user and then inserting it in the link list.
#include <iostream>
//#include <fstream>
using namespace std;
#define LEN 100
////////////////////////////////////////////////////////////////////////////////////////////////////
class employee{
[Code] ....
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Apr 11, 2014
I have a class called Question:
#include <string>
#include <vector>
using namespace std;
class Question {
string title;
vector<Thing*> posAns;
vector<Thing*> negAns;
[Code] ....
error: no instance of overloaded function 'std::vector::push_back()' matches the arguments list
argument types are (const Thing *)
object type is: std:: vector<Thing *, std::allocator<Thing *>>
So it cannot be constant, what if I just leave it non-constant? Will it be safe?
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Aug 4, 2014
Why do I get the error 'rec' cannot appear in a constant-expression ?
I have the following definitions:
... string rec[6];
list<rec> musicList;
...
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Feb 8, 2014
I'm currently trying to access a variable contained within a base object from another completely different object and I continually get error messages. I'll attempt to put up the important code since it's contained within fairly large classes. From the Base .cpp file. ObjectPosition:
void ObjectPosition::init(float x,float y, float speed, int boundx, int boundy, float hit, int lives, bool live) {
ObjectPosition::x = x;
ObjectPosition::y = y;
ObjectPosition::speed = speed;
ObjectPosition::boundx = boundx;
ObjectPosition::boundy = boundy;
ObjectPosition::hit = hit;
ObjectPosition::lives = lives;
ObjectPosition::live = live;
}
This is the initialization function for the BaseObject. All objects are inheriting these variables which are Protected within the ObjectPosition class.Then they are initialized within the Pig class thus wise:
void Pig::binit(float sx,float sy, ALLEGRO_BITMAP *simage) {
//Sets all ObjectPosition Variables
ObjectPosition::init(800,900,10,80,40,40,10,true);
smaxFrame = 4;
scurFrame = 0;
[code]...
I tried to initialize the boundx through the pig via pinitx but I get errors and I can't access through the pig to the object position to the boundx.
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Apr 29, 2013
I'm trying to write a function that takes two linked lists and creates a third one with only the common elements.
It assumes the first list (the caller) has no dups, but it doesn't seem to be working. The program doesn't crash, it just hangs when it is supposed to display L3 (the third list)..everything else runs and is displayed fine.
template <typename T>
LList <T> LList <T>:: common (LList <T> &B)//common fct
{
Node <T> *hunter1 = Head;
[Code]......
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Jan 28, 2015
I'm working on collision detection for a game in SFML. I successfully designed a Spatial Partition grid to speed up the collision test, in the following of this tutorial: [URL] ....
But now I have an issue with one aspect of it: Going through a vector of objects and testing all the OTHER objects in the vector against said object. The author puts it into psueudocode here:
For each tick of the clock
For every object in the game
Get all the other objects in the same grid square
For each other object in the same grid square
I have trouble with the last line, because in iterating through a vector I am not sure how to skip over the current object. Here is my own code (a couple of sysntax errors but this is a c++ question not an SFML question):
//for every moveable object
for(int i = 0; i < rects_.size(); i++){
std::vector<sf::RectangleShape> posibleObjects_; //this will be a vector of WorldObjects in a real game
//for every object in that object's gridsquare
for(int j = 0; j < rects_.size(); j++){
if(rects_[i].intersects(rects_[j])){
//collision
} } }
The problem is, a collision will always be reported because somewhere in the vector the object will eventually check against itself which is always a true collision. What is the correct way to do this?
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Sep 19, 2013
trying to understand operator overloading, and i wrote some code just to define a "-" operator to do a simple subtraction. SO, i wrote a program that can perform a subtraction between two objects and put the result in the third object. now I Just cant show the result on the console. And also can anyone define the meaning of [b1.x], like I want to know am I assigning the value to the "b1"object or the x variable? This is a very concept that I need to understand.
#include<iostream>
using namespace std;
struct Ok
{
int x;
int y;
};
Ok operator-(const Ok& a , const Ok& b)
{
Ok result;
result = (a - b);
return result;
}
int main()
[Code]...
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Jun 29, 2013
I have a linked list comprised of chars like so...
Code:
node1 - "p"
node2 - "o"
node3 - "p"
I need a function that will take in three perameters...node *replaceChar(node *head, char key, char *str)Stipulations of this function. head is the head of the list, 'key' and 'str' are guaranteed to contain alphanumeric characters only (A-Z, a-z, and 0-9). str can range from 1 to 1023 characters (inclusively). So if I call this function with these perameters..
Code:
node *head == /*the head of the list to be examined*/
char key == "p"char *str == "dog"The new list will look like this...
node1 - 'd'
node2 - 'o'
node3 - 'g'
node4 - 'o'
node5 - 'd'
node6 - 'o'
node7 - 'g'
All instances of 'p' were replaced with 'dog' I have a toString function which takes in a string and converts it to a linked list and returns the head. So assume that you can call the function on str = "dog" so...
Code:
toString(str) == /*this will return the head to the list made from the str*/
If it's unclear what my question is...I am stumped on how to write the replaceChar function the one that takes in three perameters..
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Jun 18, 2013
So I have a Class named Subject, wich I used linked list to keep the objects. Now I have another Class called Tests which I should register a test by the Subject class, so I made a search like this:
List obj; //it's the object to access the List class, which manipulates the
//nodes from Subject.
obj.currentPtr=obj.firstPtr;
while (obj.currentPtr!=NULL) {
if(obj.currentPtr->nameSubject==value) //searching if there's a
return obj.currentPtr; //name equal to provided
obj.currentPtr=obj.currentPtr->nextPtr;
}
return 0;
I've made a similar process for Subject. But in this when I access the firstPtr, it's shown to be 0, once I have already the list of Subject and it should not be zero. What's wrong?
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Dec 31, 2014
Code:
// Write a function called insertEntry() to insert a new entry into a linked list.
Have the procedure take as arguments a pointer to the list entry to be inserted (of type struct entry as defined in this chapter), and a pointer to an element in the list after which the new entry is to be inserted.
// The function dveloped in exercise 2 only inserts an element after an existing element in the list, thereby prenting you from inserting a new entry at the front of the list.
(Hint: Think about setting up a special structure to point to the beginning of the list.)
#include <stdio.h
struct entry1 {
int value;
struct entry1 *next;
};
[code]...
This is a working version of the exercise, but I don't think I'm doing what's asked. I was able to add an element to the beginning of the list using an if statement, not creating a special structure that points to the beginning of the list. How would I go about creating a special structure that points to the beginning of the list to add a new element at the beginning of the list?
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Apr 14, 2014
I have a data structure defined up here called this:
typedef list <classSpec*> ClassSpecList;
I'm trying to add stuff into the list here based on functions that return certain values of that match the same data type. In one function, I have a list pointer object defined here and I have another statement that calls a function.
ClassSpecList *answer = 0;
classSpec *thisanswer = parseClass(br);
Basically I'm trying to add the results of what thisanswer returns into my main ClassSpecList. Problem is, when I try
answer->push_back(new classSpec (*thisanswer));
It compiles but I get a seg fault
When I try somethign else like:
answer->insert(ClassSpecList.begin(), *thisanswer);
I keep getting primary expression errors and I do not know why. I even tried it with other list made without typedef and I still get those.
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Feb 20, 2015
Can distinguish between character constant and string constant giving examples
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May 30, 2013
I'm working on a linked list and was wondering how this looks to everybody else for a deleteList function.
void deleteList(Node* head)
{
Node* iterator = head;
while (iterator != 0)
[code].....
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Mar 13, 2014
I've a big problem. I'd like to generate of all permutations of objects present on my list and i don't know how to do this. I've found a few examples, but i can't use them in my code...
#include <iostream>
#include <string>
#include <list>
#include <fstream>
#include <cstddef>
#include <cstdlib>
#include <iterator>
using namespace std;
class Item {
private:
[Code]...
Input file with objects:
3
2 0 0 4
5 0 1 5
3 0 2 6
and output should be:
2 0 0 4
5 0 1 5
3 0 2 6
2 0 0 4
3 0 2 6
5 0 1 5
3 0 2 6
2 0 0 4
5 0 1 5
etc... 3! so 6 permutations for this example.
I was 'fighting' with this for few days, and I'm so downcast.
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Nov 6, 2014
I've been struggling with an object when trying to add it to a list with [Listname].push_back. You see, I have a list with some objects that will be rendered in the screen (Called objects) and a function to create a text box with some text. The function in question is the following:
void reprEv(int evNum, ALLEGRO_BITMAP *txtbxim) //Event to call, default text box image.
{
textBox *txtBox = new textBox("Line 1 ", "Line 2 ", "Line 3 ", "Line 4 ", "Line 5 ", textboximage);
objects.push_back(txtBox);
[Code]....
(txtNum is increased then space is pressed, and when certain screen (maxScreen) have been shown, then it will go to the playing state)
My problem begins when the text box is created, because it's supposed to add only 1 text box to objects list, but instead adds hundreds of text boxes to objects.
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Oct 31, 2014
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public List<Order> Orders { get; set; }
public Customer() {
Orders = new List<Order>();
}
}
This object is called as
var cust = new Customer
{
Id = 1, Name = "Khatana", [b]Orders.Add(new Order())[/b]
}
I want to ask, Orders.Add(new Order()) is a wrong way, but why..!!... as List<Order> already has been initialized in Customer constructor, then why it is again required to be initialized in object initialization.
Is this a correct way
List<Order> orders = new List<Order> {aaa.....bb....cc};
var cust = new Customer
{
id = 1, Name = "Khatana", Orders = new List<Order> { orders }
}
Why we need to initialize a list in an object initialization, where as the list has been already initialized in object constructor.
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Nov 4, 2014
I've changed up my code to the retail checkout WFA I am trying to make. I have an item list filled with objects of the now globally accessible 'Item' class, but I'm having trouble.
Essentially, I want to send an object of the item class chosen from a dropdown menu to form2, where I will fill in certain blank attributes with data entered in form2's text boxes and comboboxes. The problem, it seems, is I need another itemlist in form2 that will hold the object being passed to form 2, so I can then pass all the information to textboxes on form3 (the receipt/review page). It's been more than a year since I coded with C#, and I've forgotten quite a bit. I was also not able to find any tutorials on building an item list without an associated combobox or droplist, which is what I need.
This is my item class (minus most of its properties so the page doesn't stretch).
class Item {
public string prodName;
public string fName;
public string lName;
public string ccNum;
public string ccProv;
public string shipAddr;
[code] ....
For anyone who didn't see my last question, I'm in a User Interface Design class, not a C# class. I know this probably isn't the best code out there, but for my purposes the program just needs to compile beginning to end and pass the data like it should.
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May 15, 2013
I need to make the functions using these function prototypes. I am mainly having problems with GetFirst() and SwapData() but how to do it..
Header File with Prototypes
Code:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
/**
* @file
* This file provided a doubly-linked list implementation capable of storing any arbitrary data.
* The list implementation relies on a chain metaphor: a list is merely a sequence of links
* (ListItems) and there is no separate construct to represent the entire list, each ListItem in it
[Code]....
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May 7, 2013
I read an article on linked list here: C Linked List Data Structure Explained with an Example C Program
Code:
struct test_struct* search_in_list(int val, struct test_struct **prev)
{
struct test_struct *ptr = head;
struct test_struct *tmp = NULL;
bool found = false;
}
[code].....
What is "if(prev)"? Wouldn't "prev" always have the same value? Secondly, if tmp is NULL (which will be the case when the loop if(ptr->val == val) finds a match the first time it is run), is *prev assigned a NULL?
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Jan 2, 2014
I'm having a small issue here with my linked list.I built a linked list with strings and it worked perfectly.Now since i'm using strtok() to separate the string.for now here's what i've got:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct dict_word *word;
typedef struct node *Node;
typedef struct double_linked_list *DLL;
}
[code]....
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Jan 6, 2014
I have the codes for the functions: "Given the functions that we have discussed and defined in the class and the code that we have created, create the code for the Delete Node function and the Search function. Create an application that will incorporate all the functions that we have discussed and the new ones that you need to create. The application should allow the linked list to be built initially from a text file. The application should then allow for the user select an operation to perform. The acceptable operations are
- to search for an item
- to delete an item
- to enter a new item
- to exit the application
After the initial build and loading of data from the textfile, the application should print a listing of each item in the list and the node that it is located in. after a delete or insert, the application should display an output of the list again showing each item in the list and the node that it resides in.
The data item for this problem will be the inventory structure that we created in class and the data is in the inventory file that you already have downloaded."
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Mar 7, 2013
I am having difficulty getting my program to run. I have looked and looked many times trying to figure out what I am doing wrong. I have a hunch that it's my load function that's acting up, but from my perspective, my creation of my singly linked list looks good. From the creation of my singly linked list, does anything stand out as being abnormal?
Code:
typedef struct Node {
char word[LENGTH+1];
struct Node *Next;
} Node;
}
[code]....
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