I have a function :
void UpdateNotefications(vector <string> &Notefic)
Where I change a vector...
I called it with a thread :
thread t1 (UpdateNotefications, Notefic);
t1.detach();
Though I see that inside the func, Notefic has a val, and outside, it is still empty (after the function is over)...
Can local variable be passed as the parameter for a new created thread procedure? Here is the example code:
Code:
void CDLG::some_function()
{
CString strFileName="abc.doc";
//local variable, can it be valid for being passed into the following new thread???
//Can strFileName still be accessed from within the stack of thread procedure?
::AfxBeginThread(ProcessContentThread,(LPVOID)&strFileName);
}
[Code]...
There is another method using variable on the heap,
Code:
void CDLG::some_function()
{
CString strFileName="abc.doc";
CString* pstrFN=new CString(strFileName);
::AfxBeginThread(ProcessContentThread,(LPVOID)pstrFN);
}
[Code]...
I test these code, both methods work as expected, but I doubt whether the first method is a good way. OR if only the second method is the correct way to pass a parameter to a thread.
I am going to read some codes about image processing and I need to understand functions like this one below?
BOOL Trans_Geo_Affine(CImage *pImgSrc, CImage *pImgDst, BOOL bMatrix,
BOOL bHvInversed, double fScale_xx, double fFlex_xy, double fSkew_yx,
double fRotate_yy, double fTx, double fTy, int nInterpolation, BOOL bResize, BYTE cFill)
[URL]
two parameters, CImage *pImgSrc and CImage *pImgDst. I think they are class pointers and the function is passed by reference. What should I learn to understand this function and its parameters? How should I use this function? how to use the function with two parameters CImage *pImgSrc and CImage *pImgDst.
I have a list of Strings that are passed to a method consecutively by reference from a class. I want to get the string value passed to the method at a point in time. The reason is to perform an if statement.
//this is the class that holds that holds the constants.
using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace xxx.Functional.xyz.Login {
public class Constants {
public static String Username = "paul";
public static String Code = "4";
[code].....
I have to write an example in which you use a function having as argument a pointer passed by reference in C++. Can you provide an example like this:
funz.h : void funz( int *&a );
funz.cpp : ? (1)
main.cpp:
#include "funz.h"
#include <iostream>
[Code]...
as I write in (1) and (2) ?
I currently have multiple functions that use globally declared arrays in my code.
I want to turn them so that arrays are no longer globally declared, but instead are passed by references to the function.
And I have a function caller inside main, and other functions are called within the function.
Essentially, the 'Sequence' below uses linked lists to store data. If 'result' refers to the same sequence as 'seq1' or 'seq2', I want 'result' to refer to a new sequence. This new sequence can be default constructed (no copy of 'seq1' or 'seq2' is required). I can't seem to do this correctly. Also, the prototype of the function cannot be altered.
void fun(const Sequence& seq1, const Sequence& seq2, Sequence& result) {
// Check for reference to same sequence. If they are the same,
// create new sequence for 'result' to refer to
if ((&seq1 == &result) || (&seq2 == &result)) {
[Code] ......
I recently picked up multithreading with OpenMP, so it is still new to me. While processing data, I would like to store it in a vector, as shown here:
vector<int> vect;
#pragma omp parallel for
for(int c=0; c<500; ++c) {
vect.push_back(c)
}
However, since it is multithreaded, I would like (and need!) to have one dedicated vector per thread. I haven't been able to find an example of how to do this online. Is it even possible?
I am posting this simplified piece of code that is a bit confusing for me. There are two functions that I call. One shows the expected results but the result of the other one rather puzzles me.
//#define defineVecTyp Vec3f
#define defineVecTyp float
template <typename vecTyp>
vecTyp buildLaplacianPyramid(cv::Mat inputmat) {
vecTyp lapPyr;
[Code].....
Calling the function sum1 does not change the values stored in the variables val1 and val2. The output of the program is as follows:
val1= 1 ## val2= 10 // before the call of function sum1
val1= 1 ## val2= 10 // after the call of function sum1
sumOfVals= 22
This is quite obvious and as expected and I just pasted this piece of code as an example for better clarification.
However, if I call the function buildLaplacianPyramid and apply a function for Gaussian Blurring, this also effects the cv::Mat passed to the function. The line imshow("M1, after buildLaplacianPyramid",M1); therefore shows an image that is blurred. Since I am not passing a pointer to the cv::Mat I do not understand why this should be happening. I was assuming that there would be a copy of the cv::Mat M1 to be used within the function. Therefore I was expecting the cv::Mat M1 to retain its original value. I was expecting that all changes applied to cv::Mat inputmat within the function would not have any influence on the cv::Mat M1. Just like in my other example with the sum.
I have a class which I wrote and one of its object is "SerialPort" .NET class. In my MainWindow I created instance of my class called "SerialPortComm", then I send through some functions of mine, commands to the Serial Port, and I receive answers through "DataReceived" event.
But when I trying to use Dispatcher.BeginInvoke to write my data I have received (successfully), nothing shows on the RichTextBox which I'm trying to write to.
What can caused that, and How I can make it works?
SerialPortComm.cs
public partial class SerialPortComm : UserControl {
public SerialPort mySerialPort = new SerialPort();
public void Open_Port(string comNumber, int baudRate) {
mySerialPort.PortName = comNumber;
mySerialPort.BaudRate = baudRate;
[Code] ....
Example code:
Code:
#include <iostream>
#include <vector>
using namespace std;
class A{
[Code]....
I read somewhere, that we can imagine the reference as a pointer to the vector. So, my question is:
Let's assume that instance of class A, named a, was created with new. We call a.getV() to foo and then we call the destructor of a. foo is safe? Is the copy constructor of std::vector called?
Suppose I have a stl vector of ints, and I want to pass a sub-range of that vector as an argument to a function. One way of doing that would be to copy the sub-range, and then pass that copy by reference, as follows:
Code:
#include <vector>
using namespace std;
int MyFunction(vector<int> &a_vector) {
// Do something
return 0;
[Code] ....
However, it can be time-consuming to copy the elements between the two vectors if my_vector is large. So I'm wondering if it is possible to directly pass a sub-range of my_vector by reference, without having to create a new vector and manually copy over all of the relevant elements?
Okay, so for an assignment I need to write a function called find() that returns a reference to a vector. So I have vector <int> & find(string & key); If I do this, I get the obvious warning warning: reference to local variable 'lineNum' returned [enabled by default].
If I do vector<int> & find(string & key) const; I get a huge error that starts out like
In member function 'std::vector<int>& index_table::find(std::string&) const':
indextable.cpp:74:30: error: no match for 'operator='
Am I using the const identifier incorrectly?
I asked a few questions a few weeks ago about vectors and the fact that their data is stored on the heap. When a function closes, anything in its scope is destroyed, if it's passed by reference it won't be destroyed since it's outside the scope.
I have a program where I create a vector in one function, then pass it by reference to another. When I test for memory leaks, I get told I have 1 memory leak in in my start() function, and one memory leak in my save() function.
It's just a simple program that creates a vector, populates it with some numbers, then saves the numbers in a file. If I'm passing my vector by reference to another function, do I need to manually do something to avoid memory leaks? I'll post the code below.
#include <vector>
#include <iostream>
#include <iomanip>
#include <cmath>
[Code].....
I am trying to create a program that reads my file filled with random words, it then compares the words after they are put into a 2d array and sees if there is any matching words.. unfortunately the count is not working for me (in function2 and function3) and I am not sure why..
Code:
#include<stdio.h>
#include<string.h>
char function1(char words_array[][17]);
int function2(char words_array[][17]);
void function3(int pairs, char words_array[][17]);
int main( void )
{ char words_array[20][17];
int x = 0;
[Code]...
I am writing a code that creates a deck of cards using a doubly linked list. One function, newDeck(), is made to create a new deck if the user wants. I don't have any problems creating the deck and it all seems to work fine, but when I run the whole program and a separate function needs to utilize the nodes in my deck, I get an error. Trying to find where there was a problem, I tried displaying the values of a card node in random parts of my code. At the end of the newDeck function, after the whole deck has been created, the card still displays correctly, yet when I return back to main immediately after newDeck has been called, I noticed that the values of my cards changed to either random values or they became null. I found this strange because in between the end of my newDeck function and at this point, there is no extra code so it doesn't seem as if there is any way the pointers could have been changed. Maybe It's because I don't have a complete understanding of pointers yet but is there any way that pointers can change values when returning from a function to main?
newDeck(head, tail, n); //this is how I call the function from main.
void newDeck(Card* head, Card* tail, Card* n) //this is my function body
{
for (int i = 0; i < 4; i++)
{
[Code]....
Draw the total of a passed value, or value in general, without checking how many values there are individually.
Here's a pseudo-example:
int aliens = 10; // This should be changed as desired.
void drawaliens(int value) {
aliens.draw(value); // Instead of having a test of how many to draw, draw the amount there is from one check
}
I want to draw the amount of aliens passed or called to the alien draw function.
However, I don't want the function to check every possible value of aliens which could be passed before drawing, and just check the value once and draw that value.
IF x ALIENS, DRAW x ALIENS instead of...
IF 1 ALIEN, DRAW ALIEN(1);
IF 2 ALIEN, DRAW ALIEN(2);
IF 3 ALIEN, DRAW ALIEN(3);
.... and so on.
If there can be hundreds of aliens, it seems impractical to check every single possible value before drawing, and just check the value and draw that value.
So here I have a program that is supposed to basically sort out who passed and failed. I am currently stuck on the switch statement, I'm trying to count how many students received an A, B, C, etc.
Here's what I have so far:
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
void printIdInfo(ofstream &fout);
void printColumnHeaders(ofstream &fout);
[Code] ....
I have this code:
tgaManager.fileWriter.put((unsigned char)min(blue*255.0f,255.0f)).put((unsigned char)min(green*255.0f, 255.0f)).put((unsigned char)min(red*255.0f, 255.0f));
that should pass the value decided by the min function to an ofstream object, filewriter, that call the put method to print chars in a tga image file. When I open the file, all I see it is a huge black screen. You may be thinking that the values of blue,green and red are all zero but it is not the case.
With this code:
if (x==50 && y==50) {
cout << "Min BGR: " << endl;
cout << min (blue*255.0f,255.0f) << ' ' << min (green*255.0f,255.0f) << ' ' << min (red*255.0f,255.0f) << ' ' << x << ' ' << y << endl;
I get: Min BGR: 9.54167 29.9188 47.8701 50 50
Is it correct for me to make a clone of testobj in function AddTest below, before i add it to my map? What i want is an user pass testobj to me though AddTest, and after i add it into my map, i do not want to have anything to do with the original testobj anymore. I.e, they are two copies, one belong to Device, one belong to the caller, both has no link to each other.
Also regarding the GetTest method, i prefer to return a raw pointer, as i do not want to force the caller to use smart pointer. And i also do not want the caller to be able to do anything that may change testobj in the map. So i am not sure to return as const reference or make a clone of testobj on the map and return it to the user (but caller need to delete the testobj when it is not used).
Code:
class Device {
public:
void AddTest(const Test* const testobj) {
_pTest.insert("ss", QSharedPointer<Test>(test->clone()));
} const Test* const GetTest(QString str) {
return _pTest[str].data();
[code].....
Here is the code,
Code:
vector<int> vec;
for(int i=0;i<10;++i)
vec.push_back(i);
random_shuffle(vec.begin(), vec.end());
nth_element(vec.begin(), vec.begin()+7, vec.end());
No matter how I choose the second argument passed to nth_element, the elements in vec are always sorted as,
0,1,2,3,4,5,6,7,8,9
What is the use of second argument here?
I noticed that when using variadic functions, if I pass the va_arg() as parameter to a function, the parameters get passed in reverse. Is that expected?
For example, the following code outputs
Code:
1 2
2 1
Code:
#include <iostream>
#include <stdarg.h>
void foo_func(int v1, int v2)
{
std::cout << v1 << " " << v2 << std::endl;
[Code] .....
I have to write a c++ program with my own function which consists of two parameters (day, month). Function have to return number of days since the begining of this year. Using this function i have to find out how many days are left till birthday (or how many days have passed since last birthday)
This is how far i am:
Code:
#include <iostream>
using namespace std;
int cikDienu(int diena, int menesis);
int main()
[Code] ....
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] ....
when i pass a string pointer to a function such as string *str = new string(""); and pass that string to a handleElement() function e.g. handleElement(str), and i change the value in the function it simply doesn't change when the function exits as though it's passing it by value or something, even though it gives the pointer address.. I've now changed the code to use double pointers and pass the reference of the str pointer and it works but it seems ugly to use double pointers for this.
//handles when a new element is encountered when parsing and adds it to the parse tree
bool ParseBlock::handleElement(char cur, string *curString, int count, bool isOperator) {
countNode = new ParseNode(count);
//keep track of numbers and strings if they exist and insert them
if(!curString->empty()){
if(isNumber(*curString)
[code].....
I am supposed to update the value temp without using a return statement, or a global variable. I have never ran across a problem like this before and I am totally stuck. I think I'm missing something really simple and need a hint. Here is the code that was provided for "fixing".
#include "stdafx.h"
#include <iostream>
#include <cstdlib>
using namespace std;
[Code]....
