C++ :: How To Use Pointer To Function To Traverse The List
Nov 26, 2014
i am having trouble figuring out inorder traversal in this assignment. I was given this function definition in the homework i have to declare it. The problem i am having is how to use pointer to function to traverse the list.
void CBSTree<NodeType>::InOrderTraversal(void (*fPtr)(const NodeType&)) const;
void CBSTree<NodeType>::InOrder(const CTreeNode<NodeType> *const nodePtr
,void (*fPtr)(const NodeType&)) const;
//nodePtr is a pointer to a NodeType object (this is a recursive function, initially this points to the root).
//fPtr is a pointer to a non-member function that takes a const reference to a NodeType object as input, and
//returns nothing
I know without the pointer to function parameter it will be like this.
void InOrder(CTreeNode *nodePtr)
{
if(nodePtr != NULL)
{
InOrder(nodePtr->left);
cout<<nodePtr->value;
InOrder(nodePtr->right);
}
[Code]...
I just don't know how to traverse inorder with the function definition i am given.
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Aug 22, 2013
I'm trying to make a list that contains other lists. I want to use the <list> library /not my own implementation/. Here is what I do:
list<list<int>> Lists; //I create the main list
list<int> A, B; //Then I create the other lists
//After I fill them with data I add them to the main list
Lists.push_back(A);
Lists.push_back(B);
The problem comes when I try to go through A and B. I make an iterator of the main list:
list<list<int>> Iter = Lists.begin();
Then I need to make an iterator to traverse through A and B. But I can't make it. I do this:
list<int> Iter2 = Iter.begin() //But the compiler says it is not possible
How can I traverse through A and B?
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May 5, 2014
I'm trying to write a function called 'set' that sets the value of the i'th cell to val on my linkedList, and then returns the previous contents. I am stuck on it due to compiling errors:
This is my Node struct:
#ifndef NODE_H
#define NODE_H
#include <iostream>
template <typename T>
struct Node {
friend std::ostream &operator <<(std::ostream &os, const Node<T> &node) {
[Code] ....
The following is my set function:
template <typename T>
T set(Node<T> *head, int i, const T &val) {
for(int n = 0; n < i; n++)
if(head == val) {
val = i;
} return val;
} #endif
When I try to call it in the main() I get these errors:
node_utils.h: In function ‘T set(Node<T>*, int, const T&) [with T = int]’:
node_demo.cpp:26:38: instantiated from here
node_utils.h:161:2: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
node_utils.h:162:3: error: assignment of read-only reference ‘val’
So, I understand that I can't compare head & val on my if-statement -- But what do I do?
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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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Jul 15, 2013
I am currently working on a Huffman code program for one of my classes. I have gone all the way up to the point where I have created a tree but when I try to traverse it, the program crashes and says there is a segmentation fault. After running the debugger, the error occurs when I try to traverse to the left node (Line 170). The code I have below is not completely finished, I ran across the issue while testing to see that it works. See the code below:
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <vector>
#include "Node.h"
using namespace std;
void fillList(char* sent, int size, vector<Node> &vec);
[code]....
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Oct 23, 2013
I have this array which holds 3000 numbers and is initialized by assigning a random number to each element.
Code:
#include <stdio.h>
#include <stdlib.h>
int main (void)
{
int x[3000] = {rand()};
return 0;
}
I have to traverse this array so that each random value lies between -3000 and +3000 inclusive.I'm not sure how to traverse this, there is nothing in my notes discussing traversing.
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Mar 14, 2013
I'm trying to call a function via a function pointer, and this function pointer is inside a structure. The structure is being referenced via a structure pointer.
Code:
position = hash->(*funcHash)(idNmbr);
The function will return an int, which is what position is a type of. When I compile this code,
I get the error: error: expected identifier before ( token.
Is my syntax wrong? I'm not sure what would be throwing this error.
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Aug 19, 2014
I am attempting to implement function pointers and I am having a bit of a problem.
See the code example below; what I want to be able to do is call a function pointer from another pointer.
I'll admit that I may not be explaining this 100% correct but I am trying to implement the code inside the main function below.
class MainObject;
class SecondaryObject;
class SecondaryObject {
public:
[Code]....
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May 30, 2013
LinkedList* listPtr = new LinkedList;
listPtr->addNode(3);
listPtr->addNode(4);
listPtr->addNode(6);
listPtr->print(std::cout);
delete listPtr;
listPtr->addNode(5);
listPtr->print(std::cout);
When I run the program it outputs
{ 3, 4, 6 }
{ 5 }
Why does the LinkedList object that listPtr is pointing to not get destroyed??
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Jan 27, 2015
I've been playing around with making a linked list in C and am having trouble adding to the beginning of the list. For the add_beg() function: the statement "head = newNode" only works locally. This leads me to believe this is a pointer problem. However, the add_end() function works correctly. Ideally, I would like to print "0 1 2 3 4" after using the add_end(root, 0). Currently, print only gives me "1 2 3 4".
#include <stdio.h>
#include <stdlib.h>
//Create a node struct
typedef struct node {
//data
int val;
[Code] .....
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Feb 16, 2014
I have a the following in a header file.
Code:
struct SortedList{
void * data;
struct SortedList * next;
struct SortedList * previous;
int (*compareFunc)(void *, void *);
void (*destructor)(void *);
[Code] ....
In a .c file, I implemented the SLCreate function.
Code:
SortedListPtr SLCreate(CompareFuncT cf, DestructFuncT df){
struct SortedList item;
item.data = NULL;
item.next = (struct SortedList *) malloc(sizeof(struct SortedList));
[Code] ....
In main.c, I try to do the following:
Code:
SortedListPtr list = SLCreate(&compareInts, &destroy);
A bunch other code that does not alter list or it's contents at all.
struct SortedList item = (*list);
void * data = item.data;
if (data != NULL) {
printf(Why did data become not null???
"); }
How come my variable data became not null anymore when I haven't altered it at all....
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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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Feb 17, 2014
This code works:
//void Fighter::LoadAnimation(...){
std::list<SCML_SFML::Entity*> entities;
for(std::map<int, SCML::Data::Entity*>::iterator e = data.entities.begin(); e != data.entities.end(); e++) {
SCML_SFML::Entity* entity = new SCML_SFML::Entity(&data, e->first);
entity->setFileSystem(&fs);
entity->setScreen(&window);
entities.push_back(entity);//problem line
}
}
But if i change entities to a member variable, std::list<SCML_SFML::Entity*> Fighter::m_entities, it does not. Instead i get a write access violation when i try to push_back(entity). i need it to be a member variable because i need to use it in other member functions.
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Feb 27, 2015
I am having trouble modifying a linked list. I am writing a function to delete the last node from the linked list, but it gave me incompatible types error.Here is my struct:
Code:
typedef struct PCB{
int id;
struct PCB *next;
struct PCB *prev;
}PCB_rec, *PCB_p;
Here is my function to delete the last node (given the pointer is pointing at the last node of the list):
Code:
void del_last_node(PCB_p *process_list){
PCB_p temp = process_list;
if (temp->prev != NULL){
temp = temp->prev;
[Code] ....
And here is how I called the function:
Code: del_last_node(&process_list);
It gives me the following errors:
initialization from incompatible pointer type at line:
PCB_p temp = process_list
assignment from incompatible pointer type at line:
process_list = temp
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Jan 14, 2014
I am getting and infinite loop for loop pointer variable current which points to head and is incremented by current->next in while loop. I use the pointer variable the same way in my display routine and it works. Here is listing of code.
#include "stdafx.h"
#include<iostream>
struct node{
int data;
node *next;
[Code] .....
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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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May 19, 2014
I am trying to write a generic linked list in c, but for some reason i keep getting errors saying "incompatible pointer type. This is the code and erros:
#ifndef SLIST_H
#define SLIST_H
#include <stdlib.h>
typedef struct {
void *data;
slist_elem *next;
[code]....
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Feb 13, 2014
int example (int [], int, *int,*int,*int,*int);
int main () {
My code will be here
example (int array[], int size, &a,&b,&c,&d); // Like this??? I try it didnt work
[Code] ....
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Mar 19, 2013
I searched the web for error: C3867... and the discussions where murky or obscure.
My code excerpt is:
#pragma once
#include <windows.h>
#include <stdlib.h>
#include <process.h>
void PutUpfrmIO(void *);
namespace WordParsor {
[Code] .....
I get the generic message:
error C3867: 'WordParsor::Form1::PutUpfrmIO': function call missing argument list; use '&WordParsor::Form1::PutUpfrmIO' to create a pointer to memberc:userskingc++wordparsorwordparsorForm1.h... and the suggestion fix generate another error.
One person suggested the gcroot<> object wrapper... but I do not know how to modify/declair the function or its argument type.
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Mar 6, 2015
I tried to use pointer with a function but I guess I am missing out on something
Code:
#include<stdio.h>
int add(int *a,int *b){
int *c,*d;
*c = *c+1;
*d = *d-1;
[Code] ....
And this one too
Code:
#include<stdio.h>
void add(int *a){
int *c;
c = c+1;
[Code] ....
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Apr 1, 2014
I was wondering what magic does a * pointer before function actually do? Today our programming teacher asked us to look into it and explain it in the next class!
#include<iostream>
using namespace std;
int *binary(int []);
[Code].....
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Jan 24, 2013
How can we assign a pointer to a function? const char* function_name(), here what exactly does the pointer point to?
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Feb 25, 2015
Code:
void dereference(int* a, int* b)
{
a=b;
}
int main(int argc, char **argv)
[Code] ....
Why isn't f and d the same after calling "dereference(f,d);"
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Nov 21, 2014
As the title says, i'm using a function which returns a pointer to a struct:
the struct is the following:
Code:
typedef struct POINT
{
uint16_t x;
uint16_t y;
}
Coordinate; the function i'm using:
Code:
Coordinate * Read_XTP2046(void)
{static Coordinate screen;
//calculations to determine the coordinates
screen.x=(temp[1]+temp[2])/2;
screen.y=(temp[0]+temp[2])/2;
// and so on...
return &screen;}
The question is: how do i catch this pointer and make it into a Coordinate struct in which i can read the x and y.
In my main program i would do the following:
Code:
Coordinate cor;
cor = Read_XTP2046();
This does not work, as the function returns a pointer, but how to transform this pointer into a Coordinate struct.
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