How this code work bcoz when pointer variable assigned in called function and how different values get as resultant output, ans 2 97 for below code. How the code wil execute so that i can validate ans
#include <stdio.h>
int main() {
int i = 97, *p = &i;
foo(&i);
printf("%d ", *p);
[Code] ....
I need to create the following brain damaging abomination:
I need a function pointer type to a function that has an argument of the same function pointer type and returns the same function pointer type.
The purpose is to enable a type of subroutine threading scheme for a small application specific scripting language. The question could just as well have been posted to the C forum.
This syntax works, but Payload is a generic type which I can coerce into the right pointer type via a cast. This is ugly IMHO. I could also hide it as a pointer in the FlipState class since I've forward declared this.
But this is an extra indirection in a performance critical part of the code, and also ugly.
Code:
class FlipState ;
typedef PayLoad (*FuncPtr) (FlipState *fs, PayLoad P) ; This syntax blows chunks using gcc on the other hand. Code: class FlipState ;
typedef FuncPtr (*FuncPtr) (FlipState *fs, FuncPtr P) ;
[Code] .....
This is hardly surprising. The compiler could not possibly understand what I was defining in the typedef. I think what I need is some kind of way to forward declare a function pointer type and then redefine it properly.
Is such a think even possible or am I just SOL? This one is mind boggling. We know how to do this with classes or other complex data types, but the syntax eludes me for both C++ and C.
In my code, I have a function like such: int function1(int* a, int* b). I am wondering how to call it in int main.
View 3 Replies View Related#include <stdio.h>
#include <stdlib.h>
int size_b_row1;
int size_b_col1;
int main(void) {
double C[4][4] = {{1,3,5,2},{7,6,2,2},{1,2,7,3},{2,3,5,3}};
double TC[4][4];
transpose(C, TC);
[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 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 am doing a problem where I need to use arrays of string objects that hold 5 student names, an array of one character to hold the five students' letter grades and five arrays of doubles to hold each student's set of test scores and average score.
When I try to run it, I get these five errors.
error C2660: 'getTestScore' : function does not take 3 arguments : line 39
error C2660: 'getTestScore' : function does not take 3 arguments : line 45
error C2660: 'getTestScore' : function does not take 3 arguments : line 51
error C2660: 'getTestScore' : function does not take 3 arguments : line 57
error C2660: 'getTestScore' : function does not take 3 arguments : line 63
what is wrong.
Here's my code.
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]....
I am a bit confused about how specific one must be with arguments when declaring a function. I'll show you two functions from the book I'm using to learn C to show you what I mean.
Example 1 (greatest common denominator function):
Code:
void gcd (int u, int v) {
int temp;
printf ( "
[Code] ....
So in that function, there are exactly two arguments, because that's how many arguments the algorithm to find the gcd takes. No problem there, makes sense to me. Then further in the chapter on functions I run into this,
Example 2 (square root function):
Code:
float absoluteValue (float x) {
if ( x < 0 )
x = -x;
return x;
[Code] ....
In this second example, we have a square root function that is preceded by an absolute value function. The absolute value function has the one argument, "float x", however when this function is called within the square root function, the arguments "guess * guess * -x" are passed to it. I'm confused how this absolute value function is working with all of that inside it, when it was originally declared with just "x." The only possibility I can think of is that this expression is treated as a single unit, but I'm not sure.
I am actually developing an nginx module in C.I am not to bad in C, but i got a big problem to pass argument to a vadiadic function.This function look like the well good old printf, but you put a buffer as first argument, the last address to stop to put data as second argument (in my case it is the last adress of disponible memory), a string that look like one in printf, an the other argument after.Here is the problem, the 4th last argument does not have the good value. In fact, It seem to be random value from memory. I Use gcc (Debian 4.9.1-19) 4.9.1.
Code:
/* ngx_html_log.h */
#ifndef NGX_HTML_LOG_H
#define NGX_HTML_LOG_H
#include <ngx_vasm.h>
}
[code]...
I'm trying to create a callback wrapper for pointers to member functions of any class by using templates, std::function and std::bind. This will be used to send incoming sf::Event's to classes who register callbacks with an event manager. I based my code off of the example on this page: URL.....Here's what I have:
class EventCallback
{
std::function<bool(const sf::Event&)> func;
public:
template<typename T>
EventCallback(T* object, bool(T::*func)(const sf::Event&)) { func = std::bind(func, object, std::placeholders::_1); }
bool run(const sf::Event& evt) { return func(evt); }
};
[code]....
What I have is a main function that takes input characters from the command prompt during the main function call, and coverts it to an integer array a using atoi. (starting at the 2nd character - the 1st is reserved for another call that I plan to reference later, and the 0th is obviously the ./function). A function is then called to find the mode of an array (the range of values in the array is 1-30). Now, when I run the whole thing, I get a segmentation fault (core dumped) for even number of arguments. It's late and I've been staring at it for too long...
Code:
#include <stdio.h>
#include <stdlib.h>
int get_mode(int a[], int count);
[Code]......
I'm not a programmer, at least, not a good one. I'm a researcher and I need to implement this function and test it and use it for my research. I tested some clustering methods in JAVA and Matlab and also I want to test it on C. I don't know too much about programming, especially about C, I know nothing. I tried to implement some basic methods but I failed.
It's all about K-Means Algorithm. I'm working on a disease and I'm trying to find ways to early diagnosis. Anyway, these are details. The thing is, I found a 'free to use' function but I don't know how can I use it. I tried to learn something from Net, I downloaded a compiler, I paste the code and I get many errors... And I heard that I have to do some "calling function" stuff but I don't know how to..
The code is in the link below: URL....It's not imperative that using this function, it can be another one but it had to written in C.
I am supposed to get 2 numbers then have the person choose what they want to do to the numbers. Here is the code:
//Mike Karbowiak
//12/24/13
//Mathematics
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <algorithm>
[Code] ....
The errors I am getting so far are:
error C2660: 'Add' : function does not take 0 arguments
error C2660: 'Subtract' : function does not take 0 arguments
error C2660: 'Multiply' : function does not take 0 arguments
error C2660: 'Divide' : function does not take 0 arguments
I am working on a project in a group at a university. We are creating a GUI in Java where the user can enter parameters. Then we want to be able to pass these parameters to a function inside our C/C++ program, that does the rest. How do I do this? So far I have managed to call a simple helloworld-function by using JNI, dll and a javah tool that create a header file from a java file. I define the helloworld-function in C and call it from Java.
Java file:
package helloworld;
public class HelloWorld {
private native void print();
public static void main(String[] args) {
[Code] ....
My problem is that I do not know how to call the helloworld-function with parameters. I guess that this is a special case when using JNI and a . dll. How do I pass simple char- and int-arguments from the Java class to the helloworld-C-function?
i'm trying building my how Write() function:
template <typename T>
....
Write(T Argument1[,T ArgumentX])
how can i calculate the numeber of Arguments added? (in C we used an argument for tells how many we putted in a function, but not in these case)
I keep getting this error in my code. I believe it is because to use pow(x,y) both x and y have to be double, but how do i put that into my formula under calculations?
#include <iostream>
#include <cmath>
#include <iomanip>
#include <string>
#include <fstream>
using namespace std;
int main() {
// Declaration section: Declaring all variables.
[Code] ....
I have a button that calls a delete stored procedure with only two parameters. I can run the stored procedure via SQL manager and know it works. But, when I call the stored procedure from a sqldatasource on the .aspx page I get this error: Procedure or function has too many arguments specified.
Here is my code:
<asp:SqlDataSource runat="server" ID="sqlAuthorsInfo" ConnectionString="<%$ ConnectionStrings:Authors %>"
ProviderName="<%$ ConnectionStrings:Authors.ProviderName %>"
SelectCommand="FindAuthors" SelectCommandType="StoredProcedure" DeleteCommandType="StoredProcedure"
DeleteCommand="Remove_Authors">
<SelectParameters>
[Code] ....
Here is how the stored procedure looks - it is very simple:
DECLARE @authorcode int, @authorid int
DELETE FROM Requests
WHERE authorcode = @authorcode
AND authorid = @authorid
What is wrong? How do I resolve this???
As we know in C there is no checking if values passed to a function that takes enum are correct, that is if they have been defined in this enum. Example from Enums in C | Occasionally sane ([code] tags don't work on my fx 18.0.1 this is why I put in on pb): [URL] ......
Here c - How to check if an enum variable is valid? - Stack Overflow they say that common convention is add check whether value passed as the parameter is not bigger than the maximum value in enum. But how about situations when enum is composed of numbers from 1-20 and then from 500-510?
what should be the prototype for the following function.
Code:void addition(int x, ...);
I am getting compilation errors. I have written the prototype as :
Code: void addition(int, va_list);
Say I have a function pointer with this definition:
void ( *pressFunc ) ( void*, void* );
And i did this function:
void functionWithOneArg ( void* testPtr );
And i did this
pressFunc = &functionWithOneArg;
One. Would C actually let me do this? ( Assigning a function with one argument to a function with two )
Two. If so, what would happen to the second argument that is passed the function when its called? Does it just get 'cut off' and only the first argument is passed?
In the following code:
#include <iostream> // For stream I/O
using namespace std;
int function(int a) {
return a;
}
int main() {
function(int b);
}
Why is creating a variable inside the function argument list not allowed. Any reason other then for the language syntax or just for the language syntax?
I always have confusions while using pointers with functions both as arguments and as return type.
View 1 Replies View RelatedI have some trouble with DLL. I created a dll with function
double square(const double * args)
and then in my application defines
typedef double (*MyFunct)(const double *args);
I use LoadLibrary and GetProcAddress to get the function address and cast it to MyFunct. Everything works fine except that when I pass a double *, for example 0x08800350, to the DLL function, the argument becomes totally something else, for example, 0x0aa00460.
I have no clue what happens to the argument value.
In C you can just load and call the address of a function without defining its arguments like this:
Code: int (__stdcall *pMessageBox)();
int main() {
HMODULE h=0;
h = LoadLibrary("user32.dll");
pMessageBox = GetProcAddress(h, "MessageBoxA");
// MessageBoxA
pMessageBox(0, "MessageBoxA has been called!", "MessageBox Example", MB_OK);
return 0;
}
In C++ the same code gives "too many arguments for call" error unless you define the function first with its parameters.
Is there a way to do it the same way in C++?
In class, we have learned how to set up the main method so we can convert command line arguments to integers and utilize them. Here is an example of a method we learned to store command line arguments as integers in an array:
Code:
int main (int argc, constchar* argv[]) {int i;
int a[argc - 1];
// Fill the array with the arguments on the command line
for (i = 0; i < argc - 1; i++){
a[i] = atoi(argv[i + 1]);
[Code] .....
I understand that there are probably better ways to do it than using the atoi function, but for our purposes, the professor said this was okay.
Now, I am being asked to create a separate function to perform the same task (store integers in an array). I was told I would need to declare the array "out in the main program", and that the function would need to take at least 2 arguments: an array, and an array size.
Firstly, what should my return value be? My professor gave a hint that it would be important for me to figure out what the return value is, but I don't see why it would be anything else than void.
Also, wouldn't I need a third parameter? Perhaps the integers that are being stored in the array? (But how would I represent this as a parameter)?