whats the difference between functions as pointer and normal function, eg:
void function1(void)
void *function1(void)
What is the difference between the two?I'm doing parallel programming and we use pointer functions (void *function1(void)) when calling threads. I want to why it is done.
So I have an object of class NRG (Normal Rand Generator) which takes, as an argument to it's constructor, an object of class RG (Rand generator).
template<typename RG>
class NRG {
RG rg;
public:
NRG(RG r):rg(r){}
double operator()();
An object of this class will return a normal random when it's member function operator()() is called:
template<typename RG>
double class NRG::operator()() {
static int flag = 0;
static double N2 = 0.0;
if(flag==0)
[Code] ....
However, when I run this I get an error which says:
C:UsersavadhootDesktopb.cpp|69|error: 'template<class RG> class NRG' used without template parameters|
C:UsersavadhootDesktopb.cpp|69|error: expected identifier before 'operator'|
C:UsersavadhootDesktopb.cpp|69|error: two or more data types in declaration of 'operator()'|
||=== Build failed: 3 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
I just wanted to know what's the difference between these two types of main functions:
Code: int main (int argc, char** argv){ ... }
Code: int main (int argc, char* argv[]){ ... }
My question is why when I attach this function to an object, it produces a different result? If I attach div() to goose, it produces 4 as the value of alpha, but if it's not attached, it produces 3, why is this?
main.cpp
#include <iostream>
#include <cstdlib>
#include "main.h"
using namespace std;
int main() {
Oreo fox;
[code].....
I have these arrays in a driver to use for testing:
insert Code:
#include <stdlib.h>
#include <stdio.h>
#include "TwoD.h"
int main() {
/* Initialization of LCV's */
[Code] ....
If I want to test these functions in this header:
insert Code:
#ifndef TWOD_H_INCLUDED
#define TWOD_H_INCLUDED
#define MAX_SIZE 50
/* Structure defenition for TwoD */
typedef struct
[Code] ....
I am trying to perform columnSum and rowSum, as well as twoDadd and twoDSubtract using the arrays defined in my driver. How would I do that using A and B in my driver?
I need to convert this code into a normal function that can be put into a library.
Code:
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
[Code].....
Like on line 21&22, I need to get the stuff from within the program, not through cmdline.
I just figured out that some std functions (for example: copy) need the resource and target objects have iterators to work. Otherwise, the compiler rejects. In case of two arrays, declared as:
double myA[100] = {};
array<double, 100> myB = {};
myA[0] is like a pointer, myB.begin() an iterator, if I do not make any mistake. So, what is exactly the difference between the pointer and the iterator here? They all give the access to elements.
If I need the target of copy to be an array like myA which cannot give an iterator, is there a way to make the command "copy" work for it?
I've read about the difference between the two, what one can do that the other can't syntactially, but I'm still very confused by the concept of references in C++. I'm trying to understand what is the difference in terms of undelying implementation.
Take, for example, the following code:
void foo(int *bar) {
++*bar;
}
int main(void) {
int n = 0;
foo(&n);
return 0;
} Translated into: Code: __Z3fooPi:
[Code] ....
Considering the above assembly code, and the memory that was used in both cases, I'm tempted to say that references was added to C++ to make the synax looks prettier... Where would I be wrong?
What is the difference in pass by pointer and pass by reference? As per my understanding, there is no difference much.If a function accepts pointer, then NULL check can be performed.other than this i'm not able to see any big difference..
View 3 Replies View Relatedvoid func(float arg); // arg is supposed to be in type, with no referencing, just a copy of it
void func(float &arg); // arg is supposed to be in, out type, with something contained in it already
void func(float *arg); // arg is supposed to be in-out type, with nothing contained in it already and can be NULL
void func(const float& arg) // arg is supposed to be in type, with nothing contained in it already and cannot be NULL
Am I all correct?
i'm still unclear between the difference between using pointer and a reference
I understood the concept of pointers in c in the class i took last year
and that was to change the actual value stored in the memory address Code:
void change_a(int a*){
a=6;
}
int main(){
int a=5;
change_a(&a);
}
but in c++ I've been using references in all my assignments because I don't know how to correctly use pointers in c++ I may have missed a class but I'm on spring break and would like to clear things up
so in c++
in my assignments I would call it like this Code:
void change_a(int &a){
a=6;
}
int main(){
int a=5;
change_a(a);
}
so does this change the value in the address or does it make another copy of a in my c++ code and stores 6 in that copy
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.
I made this example code to illustrate my question:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int Right(char* In, char* Out, int Position){
Out=&In[strlen(In)-Position];
[Code] ....
Well, I guess the code explains it all. I want b to be the last three characters of a using a function called "Right".
Doing exactly the same thing without the function involved works fine. I just let b point to the third last character of a.
Why does the function not work?
I get a run time error saying something about memory locations when I run this program.How can I make this program work using pointers?
//this program converst miles to km
#include<iostream>
#include "std_lib_facilities.h"
[Code]....
int (*cInts)(void*,void*);
cInts= &compareInts;
int x=(cInts)(2,5); //This wont work. I tried a bunch of other things
printf(x);
Here is the assignment: (3pts) Given the following class header file, write the class’ source code for each of the accessor and mutator functions listed. (How the functions have listed their parameters, varying between passing by reference and by value.) Don’t forget to comment your code – it counts!
class Album {
private:
char * artist; // band or singer’s name
char * title; // title of the album
[code]....
The input will be an array. My questions: First, am I on the right track?
When using (char * a) for a function, for example, this is passing the address of a, correct? so then *artist=a; changes what the address of a points to?
also, the functions are bool when I would expect void. Why? for all of the set_" " functions, the parameter is *... but for set_record_label it is *&. That appears to be a mistake to me. Is that right?
what is the difference between *& and * as parameters?
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]....
There are, or course, better ways to do this, but I need to stick to some rules:
(1) Use only pointer variables and not arrays or structs.
(2) Use the three functions shown--regardless of easier methods.
The program should ask for some input, operate on those numbers, and then display the results. I know I am confused over these things:
(1) All that syntax using '*' and '&' or neither.
(2) How to use the char type correctly.
(3) How to use a char type input as an operator (a + b).
(4) How to use the pointer of the operator variable (+,-,*,/) in an actual equation.
Code:
#include <stdio.h>
#include <stdlib.h>
// *** Prototype Functions ***
void Post_Results (float*);
void Calculate (float*, float*, char*, float*);
void Get_Numbers (float*, char*, float*);
[Code]......
I'm trying to get a rotation of a spefic point in a 3D space using 3 or 4 coordinate/vector.
For example, I want to know the rotation of (5,5,5)
Using 4 vectors for example (0,0,0), (10,10,10), or 10,0,10, etc. (3 minimum)
I have been asked to develop a program with 6 methods which I have presented below. The aim of the program is to find and generate a magic square with a given dimension. This is a console program and so the 'Main' is also provided. However, I am having a problem with my code. When ever I try to generate a magic square it continuously cycles through 'forever' and I have never yet got a magic square; no matter what dimension I enter.
I must use methods 'CreateRandomlyAssignedArray' and 'CheckSquareMatrix'. There is another method 'SearchForValue', which we were told to creat. How this can be useful.
I have provided my code below:
class Program {
static Random rand = new Random();
static void Main(string[] args) {
int[,] array = new int[5,5];
array = GenerateMagicSquare(5);
[Code] ....
Write a function that generates 1000 normally distributed (Gaussian Probability Distribution) random numbers. Range should be between -3 and +3. Numbers should be double floating point.
There's more to it than that, but I've got it from there.
I am generating random number of normal distribution (0,1) but i suspect maybe I have done it wrong. The generator I use right now is
srand(time(0));
std::random_device rd;
std::mt19937 gen(rd());
std::default_random_engine generator;
std::normal_distribution<double> distribution(0,1);
Am I doing the right thing? Whether this is a real random number generator?
The following function finds the normal to a terrain represented by a texture. I found it somewhere online , it works but i couldn't understand the math behind it. So , How (or Why ?) does it works ?
//psuedo code
Vector2 normal(x,y) {
Vector2 avg;
for(int w = -3; w <= 3; w++) {
for(int h = -3; h <= 3; h++)
[Code] ....
I have a fascination with Roman numerals and would like to create a C program that converts Roman numeral inputs to normal numbers.
I want to keep everything simple and only use the C library for the coding.
So i have to create a document where all the text is normal, but on the sides one word, a important word flashes...
how would i code that in c ?????????
oh yeah i am useing complier Bloodshed Dev C++ on windows 7
I want to generate random numbers of normal distribution and use scentence like
std::default_random_engine generator;
std::normal_distribution<double> distribution(0,1);
arrayX[i][j]=distribution(generator);
But I find that each time the array I got are the same. So how should I generate random numbers with different seedings with normal distribution?
