C/C++ :: Unable To Find The Distance Between Two Void Pointers
Jul 13, 2014
I am trying to find the distance between two void pointers, so I can follow this distance to a certain pointer in a vector when given only the previous element in that vector.
int distance = (char*) prev - (char*) first;
next = (char*) cv->elems + cv->elemsz + distance;
Basically, prev and first are void pointers. I am trying to cast them into a char, subtract the first element in the vector from the previous one, and then use this distance to determine what the next element in the vector is. However, it is not working. I am not sure how to do this. To complicate matters, prev is a const void *.
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Aug 31, 2014
I'm having issues with pointers and relationship operators in C.
I need to find a max and min value in a void function using pointers. max and min would work if they had values. mul works, because you can just do math operations with pointers.
There are 0 errors and warnings; but max and min are never going to work as is.
Clearly I'm missing something.
#include <stdio.h>
#include <stdlib.h>
void max(int *a, int *b, int *c, int *d, int *result);
void min(int *a, int *b, int *c, int *d, int *result);
void mul(int *a, int *b, int *c, int *d, int *result);
int main()
[Code]...
Your job will be to create a program that uses pointers. Your output must be done in the main function and the calculations MUST be done in the three functions. Therefore you MUST use pointers correctly.
You must declare and implement the following 3 functions. Below are the three prototypes that you must use in this program.
void max(int *a, int *b, int *c, int *d, int *result);
void min(int *a, int *b, int *c, int *d, int *result);
void mul(int *a, int *b, int *c, int *d, int *result);
The functions have the following meaning:
max
finds the max value of a,b,c,d and stores the largest value in result.
min
finds the min value of a,b,c,d and stores the largest value in result.
mul
multiplies a * b * c and divides by d. Stores that value in result.
Below is an example input/output. This input will be read in via the keyboard (use scanf).
input
output (note that user input is shown in bold)
1 2 3 4
Enter the 4 numbers: 1 2 3 4
The max is 4. The min is 1. (a * b * c) / d = 1
100 3 201 103
Enter the 4 numbers: 100 3 201 103
The max is 201. The min is 3. (a * b * c) / d = 585
Your output MUST match exactly the output below for the input from above. Your program must compile, failure to do so will result in 0 points. */
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Oct 5, 2013
[URL] ....
I've been getting these errors on two computers through four different compilers. It seems the directories arnt set up. If that's the cause, I have no clue how to resolve that.
Its a very simple prog too; it just calculates a dist, using dist formula.
#include <cstdlib>
#include <iostream>
#include <math.h>
using namespace std;
void calcDistance (int x1, int y1, int x2, int y2);
[Code] ....
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Nov 7, 2014
I am trying to find the distance of 3 dimensional bodies. I am able to find the two bodies furthest from each other, but i cannot find the bodies closest to each other.
it displays 0(it's body to itself). is there a way to negate the program from comparing it to itself?
The program works but it always find the closest body as itself. Part of the program.
for(int l=0; l<size; l++){
cout<<s[l].getName()<<endl;
int smallest=0;
for(int q=1;q<size;q++){
[Code] .....
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Jul 3, 2013
Currently I am working on a program that will find the actual distance between two points on a grid. It also determines the angle of the line segment in degrees. Now, i need it to be able to find any other points on or near the line. It will be running in a loop to find each additional point sequentially until all the points have been plotted. Unfortunately, I am not entirely sure how this is done. So far, I think that I could develop an algorithm that converts the angle into a ratio of vertical movements to horizontal ones.
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Sep 24, 2014
I have a templated container that defines a forward iterator.
Calling std::distance on these iterators will generate code that will count the number of iterations it takes to get from the first parameter to the second, by repetitively incrementing.
Internally, the iterators can easily find the distance by a simple subtraction.
What I want to do is overload std::distance for these iterators so that it will take advantage of the simple calculation rather than repetitive increments.
The simple solution of course would be to make the iterators random access, but this would require that they support functionality that is not 'logical' for the container. Access to the container only makes logical sense when iterating one item at a time in the forward direction.
Code:
#include <iterator>
template <typename T>
class Container {
public:
class iterator : public std::iterator<std::forward_iterator_tag, T> {
[Code] .....
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Nov 25, 2013
how can i use the void pointers? i understand that can recive an adress variable(&). but can recive a value?
Code:
int a=5;
void *d;
b=&a;
b=100;//???
why i can't do these?
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Feb 13, 2014
I am trying to add data to a queue with the following simplified code:
Code:
typedef struct Queue {
void * data;
int head;
int tail;
int elementSize;
My question is, how do I move the queue->data pointer to the correct memory location in order to copy given data to head? The code above inside memcpy gives med the error: "expression must be a pointer to a complete object type".
Do I need an extra pointer to be able to navigate between the queue's head and tail, and keep queue->data as a reference to the first byte of the allocated memory, or is it possible with only queue->data?
Edit. Just noticed I have mixed up head and tail. The enqueued data should probably go to the Queue's tail and not the head. However, the problem is still the same.
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May 14, 2014
As part of my ongoing c programming education, I have written a program to use void pointers in a function,
Code:
#include <stdio.h>
#define MAX_NUMBERS 10
size_t size(void *object);
int main(void) {
}
[code]....
Now I think that the result 4 is the size of the pointer, so I'm confussed as why it doesn't give me the same result as 40.
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Jan 11, 2014
I want to know how to dereference a void pointer through the way of typing it.
Lets just say that I malloc'd a huge bunch of memory and i can do whatever i want
void* randomData = malloc ( 1000000 );
And i decide to make my own virtual 'int'
I am not sure how to do this.
*( int* ) ( randomData + 10 ) = ( int ) 323453 //323453 can be an int variable aswell
Im not sure if this is the right way to do perform a dereference.
This is an overview of what has to be done:
-The pointer has to be dereferenced
-Cast the pointer as an int pointer so we can change it like a normal 4-byte int
-Perform pointer arithmetic, so that the int can be placed anywhere we want
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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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Dec 23, 2012
I know how to use functions pointers in C and C++ and I know if you have something like
char buf[] = {
0x48, 0xb8, 0x3c, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x48, 0xbf, 0x02, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x0f, 0x05
};
((void (*) (void))buf)();
That this will execute those binary instructions in hexadecimal notation BUT WHY? I don't get why that works since that's an array of data not a function?
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Jul 20, 2014
I'm quite new to C and these days I have been playing around with a linked list. I managed to make a working version using pointers, ad only for the sake of learning I was trying to do the same thing just passing the "Object reference" Here is the method that apparently doesn't work..
Code:
struct Node addNode(struct Node head){
int value;
struct Node *n;
printf("Please enter the value
");
scanf("%d", &value);
[Code]...
when I return the function i have something like: head=addNode(head)
Unfortunately it does not work the way I aspect. I suppose that there is something I have left out..
Code:
like n->next=&head
// passing the address of the head at the next pointer of the struct
head =*n
//copy the values of the new node to the old head..
There must be something wrong with this line.. return head; What have I done wrong?
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Dec 4, 2014
I missed last class on doing void functions because I got sick and im completely lost! ive being using the texts book example for a reference but its not running !
The output should look similar to this:
how much was your shirt?
20
shirt 20.00
tax =1.20
the total 21.20
Code:
include <iostream>
#include <iomanip>
using namespace std;
void getShirtCost(double shirtCost);
void calculate(double shirtCost,double taxAmount, double total, double taxamount) ;
void printReceipt(double shirtCost, double taxAmount, double total, double taxamount);
[Code] ....
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Mar 28, 2014
Code:
'test.exe': Loaded 'C:UsersPcDocumentsVisual Studio 2010Projects estDebug est.exe', Symbols loaded.
'test.exe': Loaded 'C:WindowsSysWOW64
tdll.dll', Symbols loaded (source information stripped).
'test.exe': Loaded 'C:WindowsSysWOW64kernel32.dll', Symbols loaded (source information stripped).
[Code]...
The thread 'Win32 Thread' (0x2d0) has exited with code 1 (0x1).
The program '[6040] test.exe: Native' has exited with code 1 (0x1). my code is not wrong but there is an error which ı dont understand ...where is my error?
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Jan 24, 2013
My MDI Project(VC++2010 Professional) is unable to catch errors ,though I return ,try catch block. So I developed simple dialog based application .Placed one button on Dialog and on its click written following code
Collapse | Copy Code
void CMFCExecDlg::OnBnClickedButton1() {
try {
int j = 0;
int i = 10/j;
}
catch(CException * e) {
MessageBox(_T("Hello"),_T(""),MB_OK);
}
}
But still program control does not come in catch block it simply gives error. I tried all child classes of CException but no use.I think there will be some setting in Visual Studio. How to handle exceptions
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Jan 2, 2013
Why do i get this error?
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Jun 4, 2012
I have a program (below)
int main() {
int x = 1;
char *y = (char *) &x;
printf("%d
", *y);
}
The output will be either "0" or "1" depending on the architecture of the system.When I executed on my system I got output as "1", now what is the architecture of my system is it 32 bit or 64 bit?
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Nov 11, 2013
I am suppose to find voltage by multiplying a resistance array and a current array by using a function and pointers. This is what I have so far:
#include "stdafx.h"
#include <iostream>
using namespace std;
#include <iomanip>
[Code] ....
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May 22, 2013
how would i go about writing up an equation for euclidian distance using c language. I am quite unfamiliar with the syntax's involved using squared and square roots.the equation for euclidian distance is: square root((Xv -Xu)^2 + (Yv-Yu)^2 +(Zv-Zu)^2)
The variables Xv, Yv and Zv represent the equation of vector 1 and then variables Xu, Yu and Zu represent the equation of vector 2. I have already put these into my program and i just need to know how to write that equation up there into the text file so that it works.
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Mar 25, 2014
I can't figure out the error in this code; it compiles but returns rubbish.
serge
#include <iostream>
#include <iterator>
#include <vector>
#include <algorithm>
[Code] ......
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Apr 14, 2013
Write a program that creates the output shown in the Output Layout section below. The program should create 2 points with x and y coordinates as integers, prompt the user to input the x and y values for one of the points and randomly set the other (-99 to 99 range) and output the length of the radius line segment and the area of the circle that radius defines. The program should then end. Include an SDM for the program and any other appropriate documentation.
Special Calculations:
Distance between 2 points equation:
√((p0x – p1x)2 + (p0y – p1y)2) (This requires use of the math library)
Output Layout: (bold text represents user input)
Please enter the location of your first point.
Enter a value from -99 to 99 for your x coordinate: -2
Enter a value from -99 to 99 for your y coordinate: 17
The location of your second randomly set point.
Your x coordinate: 45
Your y coordinate: -89
The length of the radius line segment from point one to point two is 115.
The area of the circle with a radius of 115 is 41546.33.
Other:
int pAx;
int pAy;
int pBx;
int pBy;
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May 15, 2014
It ougth to calculate the distance between two point (p1,p2)
"main.cpp"
#include "distancia.h"
void main () {
Point p1,p2;
[code]....
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Oct 29, 2014
In the following code I don't understand why am I splitting the y left and y right.
(closest distance between 2 points in 2D)
Am I splitting the y left and y right so that I can concatenate them afterwards and then build the strip,only according to these concatenated halves ?
PS : Finding the min. distance between sorted x right and x left works fine , only problem is with the strip.
#ifndef CLOSESTPAIR_H_
#define CLOSESTPAIR_H_
#include <float.h>
#include <math.h>
typedef struct Point2D {
double x;
double y;
[code].....
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Feb 21, 2014
i have two point P1 and P2 where i want to move P1 and P2 with keeping the distance and the position of the P2 relative to P1 i thought that when i keep the distance between the two point that involve keep in the same time the local position of P2 but when tested it does not work initial position of P1=(10.0f, 00.0f, 00.0f) initila position of P2 relative to p1 =(50,10,-8) we can get the global position of p2 ----- final position of P1 =(50,10,-8) final position of P2 in the world space =(40.31,8.06,-6.45) then we calculate the distance before and after we found that there are equal but when we calculate the position of p2 relative to p1 after and before we found that there are not equal.
how i can keep the local position and distance ?
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Feb 23, 2013
As homework we were assigned to enter the following code to calculate the distance between two points on the x and y plane. The program should ask the user to enter two points then should calculate the distance between two points and print the distance on the screen.
My program will compile correctly but when attempting to run the actual program it doesnt do anything and some how completely skips over my main function...
Code:
#include <stdio.h>
#include <math.h>
struct point {
float x;
float y;
[Code] ....
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