C++ :: Assigning Pointer In Node To Point To New Vector
May 9, 2013
I've got a struct called Node that contains, among other things, a pointer to a vector of pgm objects. (pgm is a class i've created)
struct Node {
int label;
vector <pgm> *ptr;
Node* lessNode;
Node* moreNode;
};
in another class, i create a vector and a Node and am having trouble assigning the pointer in the Node to point to my new vector.
vector <pgm> lessData;
Node* left;
left->ptr=&lessData;
This all compiles ok, but the last line in the code above causes a segmentation fault. I should mention Node is declared on its own in Node.h and what pgm is. including pgm.h in node.
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Jan 17, 2014
I was having problems changing the value of my head node I passed it as an argument as head which would be the address. The parameter was defined as struct node *head. like this
bool deleteNode(struct node *head, struct node *delptr)
I tried manipultaing pointer values to change head node value but it did not work. I saw some code online which used pointer to pointers(in code below) to change head node value it worked I dont fully understand why. Would like better understanding of why.
Would also like to know why the argument call needed &head instead of just head.
remove = deleteNode(&head,found); opposed to remove = deleteNode(head,found);
#include "stdafx.h"
#include<iostream>
struct node{
[Code].....
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Feb 3, 2013
I thought we needed to allocate memory before assigning a value to a char* and also that we needed to use functions like strcpy() to copy something into it. Then how come this works and does not crash?
Code:
#include <iostream>
using namespace std;
int main()
{
char * buf;
buf = "Hello";
cout << buf << endl;
buf = "World!!!!!!!!";
cout << buf << endl;
return 0;
}
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Aug 31, 2013
I am trying to understand the behavior of following code. Basically how does printf() prints the value rather than address.
Does initializing value to a pointer during declaration makes a difference when assigned from a variable?
Code:
1 #include <stdio.h>
2
3 int main() {
4 const char *var1 = 'A';
5 int *vint = 10;
[Code] ....
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Jul 2, 2013
In the current code,We are using pointer of union and assigning value.
class sample {
union {
short *two_int;
int *four_int;
double *eight_real;
char *one_ascii;
// void *v;
}; }
Than we assign value in following way.
sample.four_int[0] = (x + xoff); ( x and xoff and y and yoff all are integer)
sample.four_int[1] = (y + yoff);
Than we write data into file. it was working fine into 32 bit machine but it is not working 64bit machine. When I compare data and found that data is divided by 4. For Ex The File generating from 32 bit machine contain 80 than 64 bit . File contain 20.
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Mar 30, 2013
I am trying to assign a list of values to a vector:
vector<string> words;
words[] = {"one", "two", "three"};
This does not work. How can I accomplish it?
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Sep 13, 2013
In another forum, this example code fragment was stated as being an example of undefined behavior. My understanding is that a literal string exists from program start to program termination, so I don't see the issue, even though the literal string is probably in a different part of memory.
Code: /* ... */
const char *pstr = "example";
/* or even */
char *pstr = "example";
/* as long as no attempt is made to modify the data pointed to by pstr, */
/* unless pstr is later changed to point to a stack or heap based string */
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Aug 16, 2013
I have the following code.
StackElement *StackElementArray;
StackElementArray = new StackElement[iMaximumDepth];
I want to assign one element of this array StackElementArray the address of another object. For example,
voidStackMem::push(StackElement &iStackElement) {
CurrentDepth++;
StackElementArray[0] = iStackElement;
}
The StackElement class contains pointers to some dynamic arrays. When I use the assignment, StackElementArray[0] = iStackElement;, it doesn't copy the complete contents and I have to define an 'assignment operator' function to copy all the contents. I am wondering if there is a way I can assign StackElementArray[0] the pointer to the StackElement object. In that case, I will not need to copy the contents of iStackElement into StackElementArray[0] and will just copy the address.
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Nov 28, 2012
I am writing a program to play rock paper scissors, and I am trying to get a vector to store the result of a given round of play, and output it as a declaration as to who won. I can't figure out how to store the values in the vector properly, and how to use the vector as an argument to output the result of play.
Code:
#include <iostream>
#include <iomanip>
#include <ctime>
#include <vector>
#include <cstdlib>
#include <string>
using namespace std;
const string name[4] = {" ", "rock", "paper", "scissors"};
const string roundResult[3] = {"computer win", "player win", "tie"};
[Code]....
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Aug 2, 2014
I have the following:
int Allocate(int, int *);
main() {
int *Pointer;
int Elements = 25;
// this works just fine - as expected.
Pointer = (int *) malloc(Elements, sizeof(int));
// This DOES NOT - The value of Pointer never changes.....
[code]....
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Nov 27, 2014
im trying to port a code from vc6 to vs2013 and im having this error
Code:
Error11error C2440: 'initializing' : cannot convert from 'char *' to 'std::_Vector_iterator<std::_Vector_val<std::_Simple_types<char>>>' on this line
Code:
vector<char>::iterator BufIt = (char*)lpBuffer;
what i do with this is to stack fragments of data of type char* coming from a socket in buffer to a vector that acts as buffer, I do this since I transfer big chunks of data and the data gets fragmented by the nature of the sockets, I stack the data once its complete I retrieve the final result from the vector.
this code worked flawlessly for long time but now Im trying to port and compiler throws this error, whats the new way to assign a char array pointer to a iterator so i can stack it in the vector.
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Nov 30, 2014
Why is it sufficient to only have a pointer to the last node of a doubly linked list?
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Nov 30, 2014
Why is it sufficient to only have a pointer to the last node of the list?
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Mar 30, 2015
I'm having a bit of an issue here. I have a linked list where each node contains a pointer to a string (which has been malloc'd when the node was created and inserted) and a pointer to the next node in the linked list.
I'm creating a function which will free the node (or effectively delete it). However, I'm receiving a free(): invalid pointer error.
My function:
void removeNode(node *(*nodeToRemove))
{
free((*nodeToRemove)->data);
(*nodeToRemove)->next = NULL;
free(*nodeToRemove);
}
Is this how I should go about freeing this node?
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May 12, 2014
I am trying to write a basic editor program and one of the parts asks me to "process dot commands that move point in whole line increments"
Earlier it says that a point is interpreted as specifying the location between characters rather than the characters themselves. and i need to use this to implements the following:
< moves point to the beginning of the document. > moves point to the end of the document. p moves point to the beginning of the previous line. n moves point to the beginning of the next line. k deletes the current line and leaves point at the beginning of the following line.
(there was a previous part before this so i already have some code that works) and in this part I'm trying to do a switch case
ie
for
< , >, p , n and k
I guess my question is how do i make this "point" need. Ive been using vectors, so the point needs to be somewhere inside the vector. I don't think ill be able to do what i need to do with out the point.
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Jan 31, 2013
Do I really need to create a separate pointer to point to dynamic arrays?
T* temp = new T[capacity_ * 2];
T* tIter = &temp; //Do these need to be here?
T* dIter = &data; //Or can I use *(temp + i) and *(data + i)?
(for unsigned int i = 0; i < size_; i++) {
*(tIter + i) = *(dIter + i);
}
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Nov 30, 2014
Why would it be cumbersome to maintain an additional pointer to the first node in a doubly linked list?
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Nov 30, 2014
The following code compiles and runs fine till it reaches line 16 and gets a sigsev violation which I'm not sure about as to why. I have no problem passing the object of type node** into the constructor of base and storing it into the double pointer node** copy;; but when I call the function void pass(node** temp) it crashes.
#include <iostream>
class base;
class node {
private:
node** data;
public:
[Code] .....
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May 7, 2013
I have a pretty big std::vector<matrix>, where matrix is a custom class defined by me. I would like to know how much memory has been allocated to that vector at a certain point in time. Is there any way of doing this in c++?
Or is my only shot, taking a look at the task monitor of windows/unix/whatever at execution time to estimate this?
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Aug 27, 2013
I have a program that has a base class 'control' and there are 2 dervied classes 'button' and 'textbox'. How do i make a constructor in the 'button' or 'textbox' that initializes a pointer of the data type 'control' to point to the object that invokes the constructor. the code should look like this
class control {
//data
} class button:public control {
buton() {
//code for the constructor
}
}
actually i have an array of pointers of the type 'control' and as soon as any instance of a control like button or textbox is created the constructor should make an element of the array to point to the instance
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Jan 21, 2014
This code work perfectly, as follows.
Code #A:
#include <iostream>
#include <cstring>
#include <vector>
using namespace std;
typedef std::vector <void *> gr_vector_void_star;
gr_vector_void_star output_items;
[Code] .....
Output of above code #A:
char * sentence = "Angel";
for (int i=0; i < 5; i++)
{ out[i] = sentence[i]; } // error: invalid conversion from 'char' to 'char*' [-fpermissive]
It fails to compile with error message "invalid conversion from 'char' to 'char*'".
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Jan 30, 2014
Is this the correct format to point a pointer (pointer1) to another pointer (pointer2)?
&pointer1 = &pointer2
I am kinda rusty when it comes to pointers ...
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Apr 22, 2015
I am working on C# Project [Windows Form Application], to update treeview nodes from excelsheet [xls] Cell [row i, Column 3] Values, while on selecting treenode, it should update corresponding Column 4 Value [row i, Column 4]. For me, Treenode are populated successfully, but on selecting the treenode, it always display first Element of treenode [Not selected one].
Populated Treenode from Excel as: [ Update Child Nodes from Column 3 elements [Column 2 Contain Parent node name and Column 3 have Child Node name], if Column 2 Value is same as Parent node name [My Module], update the child nodeunder same Parent node.]
for (int i = 0; i < worksheet.UsedRange.Rows.Count; i++) {
string mynode = ((Excel.Range)worksheet.Cells[i + 1, 3]).Value2.ToString();
string mynode2 = ((Excel.Range)worksheet.Cells[i + 1, 2]).Value2.ToString();
[Code] ....
On selecting the Child Node, it always give 1st Parent node. Instead of Selected Node.
for (int i = 0; i < worksheet.UsedRange.Rows.Count - 2; i++) {
string mynodetext = ((Excel.Range)worksheet.Cells[i + 2, 3]).Value2.ToString();
string mynodetext1 = ((Excel.Range)worksheet.Cells[i + 2, 4]).Value2.ToString();
if (treeView1.SelectedNode.FirstNode.Text == mynodetext) {
this.richTextBox1.SelectedText += Environment.NewLine + mynodetext1 + Environment.NewLine;
}
}
How to get correct selected Node.
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Jul 26, 2014
I'm having a hard time figuring how to get my imagelist index 3 icon to display in the nodes "N1" and "V Speeds" below? So, as you can see in the attachment, the closed folder icon is currently shown which is index 0 in the imagelist. But I want index icon 2 to show in these two nodes.
treeView.BeginUpdate();
treeView.Nodes.Clear();
treeView.Nodes.Add(new TreeNode("Checklist"));
[Code].....
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Sep 30, 2014
My problem is that I have two classes that both need members from each other, so I need to use forward declaration + pointers, etc. However, trying to access a vector from a pointer throws an error.
Here's the code:
for(int j = 0; j < level->GetCollisionObjects().size(); j++){
if(fr.intersects(level->GetCollisionObjects()[j])){
rotate = false;
}
}
level is a pointer to class Level. This function is inside class GamePiece. Class Level includes class GamePiece, but GamePiece needs access to the vector CollisionObjects. This function throws a vector size error, and I'm totally lost on what to do.
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Mar 16, 2012
I have a pointer to a vector that contains instances of class Test:
Code:
vector<Test*>* testVec;
If I do this:
Code:
Test* one = new Test();
tectVec->push_back(one);
this crashes. What do I need to do to declare the dynamic memory so this works?
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