C++ :: Multiple Objects Passed As Reference To Function
Apr 23, 2013
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] ......
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Sep 28, 2014
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.
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Dec 8, 2014
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) ?
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Mar 9, 2013
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.
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Mar 22, 2013
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.
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Aug 25, 2013
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)...
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Apr 8, 2015
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].....
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Jan 19, 2012
I'm using mingw with gcc 4.4.1. I'm trying to write a function that operates only on unique objects that have been explicitly moved.
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(unique&& i)
{
std::cout << *i << std::endl;
[Code] ....
This is confusing to me because it compiles, yet my unique i is passed by R-value reference, without ever being explicitly moved. I thought named objects could NEVER be considered R-value references... Am I wrong to think that the above is extremely dangerous? After the call to "eat", my "i" has been destroyed internally, I could save by passing by value:
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(unique i) {
std::cout << *i << std::endl;
[Code] ....
But at this point, I'm paying for a (theoretically cheap) move copy, when I could be paying nothing at all... A third solution would be to overload with a const ref version, but at this point, I get an obscure linker error, when I'm really looking for a compiler error...
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(const unique&);
void eat(unique&& i)
[Code] ....
I'm actually trying to write a container that manages unique objects, and was trying to write a function that accepts only moved objects.
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Aug 20, 2014
Can I a have one pointer with two reference in it. Here's what I've got.
Code:
char* c;
char x='x' , y='y';
c = &x;
c = &y; -- or --
Code: char* c[2];
char x='x' , y='y';
c[0] = &x;
c[1] = &y;
If it's possible I want to apply it to make AST.
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Jan 9, 2015
I have a piece of code which gets multiple objects to move randomly at a designated number of intervals. I want to create a function which calculates the distance between each pair of points after that number of steps. so the distance between object 1 and object 2, object 1 and object 3, ..., object 1 and object N. then object 2 and object 3, object 2 and object 4, ..., object 2 and object N. then then object 3 and object 4, object 3 and object 5, ..., object 3 and object N and so on until the distance between all the pairs of points have been calculated.
#include <ctime>
#include <cstdlib>
#include<iostream>
#include<cmath>
#include<iomanip>
#include<fstream>
#include<vector>
using namespace std;
double dist(int a, int b);
int X(int x1, int x2);
int Y(int y1, int y1);
[Code] ....
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Feb 9, 2015
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
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May 21, 2014
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].....
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Nov 17, 2014
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] .....
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Feb 20, 2013
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] ....
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Dec 24, 2014
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].....
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Mar 24, 2015
I have the following code, but it crashes on the "data = " line...
Code:
void Test(string& data) {
unsigned char* msg = (unsigned char*)malloc(MAX_LENGTH));
...
data = string(reinterpret_cast<const char*>(msg), MAX_LENGTH);
}
I know I could just return string, but what is wrong with this code that is making it crash?
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Apr 28, 2014
So I have a small program which is supposed to write and read multiple objects from a file, but for some reason it doesn't write the information when I use "fstream" to create the object from the fstream class, but it does when I use "ofstream". Also, it doesn't read the information from the file no matter if I use "fstream" or "ifstream". I watched a video where this exact code worked just fine, but it just won't work when I run it. I'm using Dev C++ 4.9.9.2, I don't know if that has anything to do with it, I also tried it with Code::Blocks, didn't work either.
Here's the code.
#include <iostream>
#include <fstream>
using namespace std;
class Person
[Code].....
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Mar 7, 2013
Sem is a pointer to semantic which is a struct type variable. I pass the sem into function yylex so i can fill the semantic.i and semantic.s(s points to an array). The problem is that when sem->i = a; is used inside yylex function, sem->s stops showing to the array.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <iostream>
using namespace std;
union SEMANTIC_INFO
[Code] ...
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Jul 10, 2014
I'm making a .json loader for a project that I'm working on, and to simplify things, I decided to make all the root attributes named in a separate file. Here's my problem: my loading function, Add(const char* id), works just fine when I pass it a string literal.
However, when I use a function that iterates through a vector list, even with the exact same definitions as the literal, it returns the error: std::out_of_range at memory location 0x0026fb30
I've stepped through it with the VS2010 debugger about a hundred times, checked against memory locations, and just have done everything I can think of, all to no avail..
The code, with data-checking omitted:
The std::map I'm adding to:
static std::map<const char*, Item*> *s_mItems;
Initialized as std::map<const char*, Item*> *Item::s_mItems;
Add() Function (Works by itself with a literal):
static bool Add(const char* id) {
...
std::string name = node.Get("name").ToString();
std::string desc = node.Get("description").ToString();
int rarity = StrToRarity(node.Get("rarity").ToString());
[Code] ....
AddList() function, where the program always breaks:
static void AddList(std::vector<std::string> list) {
for(std::vector<std::string>::iterator it = list.begin(); it != list.end(); it++) {
Add(it->c_str());
}
}
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Jun 20, 2012
find the average of 10 numbers to an array using function .the array should be controlled by while loop?
#include <iostream.h>
float sum(float x[],int size);
main() {
float a[10];
int n=10;
[Code] .....
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Feb 24, 2015
How to check the type of argument passed to each function, checktype, in below?.
void checktype(void *p)
{
}
or
template <typename Type>
Type checktype(Type t) {
}
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Mar 15, 2015
We're assigned a project working with classes and fractions. My goal is to display a fraction in proper from based on 2 arguments passed to a class member function proper();
My strategy was to utilize the greatest common factor between the 2 arguements, then divide both the numerator and denominator by that number and then it would display.
The program actually runs, but only seems to divide the numerator and not the denominator. This in return makes my other class member functions have incorrect comparisons and sums.
Code:
#include<iostream>
#include<conio.h>
class Fraction {
friend void compare(Fraction a, Fraction b);
friend void sum(Fraction a, Fraction b);
[Code] ....
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Mar 29, 2013
I'm writing some functions pertaining to binary trees. I've used recursion once before while learning quicksort but am still quite new and unfamiliar with it. And this is my first time touching a binary tree. So my question: In my addnode function, will the return root statement at the end ever return a value other than the value passed to the function?
Code:
#include <stdlib.h>
struct tnode
{
int data;
struct tnode * left;
struct tnode * right;
}
[code]....
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Jan 19, 2013
The error is this:
#include <iostream>
using namespace std;
void add(int s);
void subtract(int d);
void multiply(int p);
void divide(int q);
[Code] .....
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Nov 23, 2013
I'm making a program that's essentially a Text-Based Fire Emblem game; it runs calculations and rolls dice and has all sorts of Goodies. However, I have hit a block to the tune of
#ifndef ITEM_H
#define ITEM_H
class Item
{
[Code]....
Up Until I called up a Sword object, it worked fine. But when I compiled it, I got an Undefined Reference to Item::Item() error in Line 8 of Weapon.cpp.
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Feb 15, 2015
#include<iostream>
using namespace std;
int &fun() {
int x = 10;
return x;
}
int main() {
fun() = 30;
cout << fun();
return 0;
}
The code outputs 10.
Shouldn't it show an error because x is created locally on stack and gets destroyed on function return?
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