C :: Static Array Of Function Pointers
Jan 29, 2015
I basically have some code that lets users register callbacks into a callback table at a specified index. There is one element in this table for each event that can trigger a callback. I basically do something like this:
In a header file
Code:
typedef struct _GMclient
{
GMcommunicator gcomm;
GMclient_callback callback_table[(int)MAX_CALLBACKS];
}GMclient;
typedef int (*GMclient_callback)(GMclient*, void*, void*);
Then I allow them to set the callback with a function that basically ends up doing this (in a .c file that includes the previous mentioned .h file):
Code:
void
GMclient_register_callback(GMclient *client,
GMclient_callback fxn,
int index)
[Code] ....
Then later when I need to invoke that callback, I pull it out of the table
Code: GMclient_callback *fxn = client->callback_table[CMD_INDEX];
However, I get compilation errors:
Code: src/gmanager_client.c:43:6:
error: a label can only be part of a statement and a declaration is not a statement...
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Aug 4, 2013
How would I pass let say 2 array pointers to a function X , allocate memory for them in X , fill them with values and get them back in my main function without creating a structure.
example:
Code:
void X(int *a, int*b){
a= malloc ...
b = malloc ...
// fill a and b
return them back to the main function
}
void main(){
[Code]...
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Apr 6, 2014
Ive recently got into function pointers, i find that they can be quite handy for making your program very 'dynamic'.
However, the syntax is very confusing for what i want to do
This is what i want to do
I want to hold function pointers inside an array, but this array is dynamically allocated ( malloc, realloc, etc )
This is the current syntax ive come up with, but i dont think it is correct
void ( **drawFunc ) ( void*, SDL_Surface* );
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Feb 28, 2014
I'm trying to create an array of pointers to pointers which will point to array of pointers (to strings) I tried
Code:
int i;
char *string[]={
"my name is dave",
"we like to dance together",
"sunny day",
"hello",
[code]...
the app keeps crashing , I don't know how to make the array-elements to point to another array-elements..
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Dec 13, 2013
I would like to know if this code is correct.
#include <iostream>
#include <string>
int say_one(const std::string &s) {
std::clog << s << ": One!
[Code] .....
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Nov 21, 2014
I have a a group of text files that are used as input into a program. Another very similar program needs the same data in a different input format. I am writing a program that will read in each line of data and parse it. I have successfully written the program in main() such that it will read until the end of file. However, I am trying to re-write the program such that the algorithm is in an external function and will read one line at a time and then pass all of the character strings to the main program. The program will not compile and I am positive it has to do with an incorrect use of arrays in passing the variable "token". I am attaching a copy of the main program and the function.
#include <iostream>
#include <fstream>
#include <cstring>
#include <stdio.h>
void Line_Parse(std::ifstream&,std::ostream&,const char* token);
int main(int argc, const char * argv[]) {
[Code] .....
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May 13, 2013
I'm trying to create an array of function pointers and then assign compartilbe functions to them, so I can just call *pf[0](xxx);
The functions are all of the type
void func01(unsigned char*, int, int)
how would I create an array of function pointers and assign the address of the functions to them? So I could call them like
ptrToFunction[i](charBuffer, 10, 20);
I've read a bit on line and I thought I could do it but so far I've failed.
It seems trivial and I feel I'm close but close isn't good enough.
I'd like to assign the fuction addresses like this:
for (int i=0; i<10; i++)
if (i==1)
ptrToFunction[i]=func01;
if (i==2)
ptrToFunction[i]=func02;
etc.
The actual logic is somewhat different than this but this close.
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May 12, 2013
The premise of this assignment is to create a menu driven, array of functions calculator. This is the code I have thus far (I haven't finished all of my comments yet, I've been to focused on clearing errors).
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/*prototypes*/
void sum (int a, int b);
void dif (int a, int b);
void pro (int a, int b);
void quo (int a, int b);
void printMenu();
[Code] .....
I am using Visual Studio as a compiler, and I have the following errors:
error C2144: syntax error : 'int' should be preceded by ')'
error C2660: 'sum' : function does not take 0 arguments
error C2059: syntax error : ')'
error C2144: syntax error : 'int' should be preceded by ')'
[Code] .....
I can only assume that I am making simple mistakes.
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May 24, 2013
I am having following pointer variable declaration
Code: Static double (*funcs[]) (double) = { sin,cos,tan,asin,acos};
Here funcs is an array of pointers to functions which take double as input and gives double as output with static as storage type am I right.
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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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Feb 11, 2013
i need a function that will work for both dynamic and static implementations of a function to get the transverse of a matrix. so far, i have this
Code:
matrix transpose(matrix m)
{
int row, col;
row = m.com_dim;
col= m.row_dim;
}
[code]....
this works well with my static implementation, but when i try it in dynamic it gives me errors. the function has to be the same for both dynamic and static implementation
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Mar 13, 2013
But it can the other way around
Code:
static_Array= dynamic_Array;
dynamic_Array = static_Array;
The second statement works and i'm able to print out both arrays with equal values but with the first
[code] static_Array = dynamic_Array;I get incompatible types in assignment of 'int*' to 'int [7]' is the error I get [/code]
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Apr 17, 2013
From my book:
"A static function might have this prototype:
static void Afunction(int n);
A static function can be called in relation to a particular object by a statement such as the following:
aBox.Afunction(10);
The function has no access to the non-static members of aBox. The same function could also be called without reference to an object. In this case, the statement would be:
CBox::Afunction(10);
where CBox is the class name. Using the class name and the scope resolution operator tells the compiler to which class Afunction() belongs."
Why exactly cant Afunction access non-static members?
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Sep 11, 2013
What are the workarounds for accessing the non-static member variables of some class(Say A) inside static member functions of another class(Say B)? I am coding in c++. Class A is derived with public properties of class B. Any pointers?
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Aug 27, 2014
I need to keep a static variable in a member function of a class that I have many objects of. I've had some trouble with it, and when I read up I found that such variables are static across all instances. Is there any way around this?
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Mar 8, 2014
What am I doing wrong with static members and methods here?
compiler errors:
1>test.obj : error LNK2005: "private: static int Test::count" (?count@Test@@0HA) already defined in main.obj
1>c:usersjamesdocumentsvisual studio 2013Projectsstatic_testReleasestatic_test.exe : fatal error LNK1169: one or more multiply defined symbols found
test.h
#ifndef TEST_H_
#define TEST_H_
class Test {
[code]....
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Oct 30, 2012
In my code, I wanted to write log exception to some file.
So I created a Utility class & wrote a static method in that to write log message to file.
public static void WriteLog(string message) {
using (FileStream fs = new FileStream(@"c:log.txt", FileMode.Append)) {
using (StreamWriter streamWriter = new StreamWriter(fs)) {
streamWriter.WriteLine(message);
}
}
}
This works fine so far but I fear if two methods call this function simultaneously.. what will happen? Also, I want to access this same Utility library in my other "WEB" projects... will it work there too?Or else.. what will be the best way to log exceptions in any project?
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Jul 18, 2012
I try to create small project in order to better understand how key word static works with templates . However some compiles errors crush my plan.
1>------ Build started: Project: 4.2b - Ex 1. Static Variable for Array Def Size. Templates, Configuration: Release Win32 ------
1> main.cpp
1>c:all myс++ha level 6solution level 6solution level 64.2b - ex1. static variable for array def size. templatesarray.cpp(40): error C2724: 'Array<Type>:efaultSize' : 'static' should not be used on member functions defined at file scope
[Code] .....
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Feb 27, 2013
So on lines 36 - 39 (The commented out functions) is where I'm sure is causing this error because once I don't comment them out pretty much everywhere Flink or Rlink is used or defined I get this error.
#ifndef nodes_Nodes_h
#define nodes_Nodes_h
#include <cstdlib>
[Code]....
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Aug 19, 2014
I have the following problem: I am using NLOpt for optimization. The API provides functions to set the objective. This is done as follows:
double objective(const vector<double> &x, vector<double> &grad, void *data)
{
return x[1]*x[0];
}
int main(){
nlopt::opt opti(nlopt::LD_MMA,2);
opti.set_min_objective(objective,NULL);
vector<double> x(2);
[Code]....
Now I want to make the function objective a member of a class:
class Foo {
public:
double objective(...){..}
};
How can I give this method to opti.optimize? If I make objective static I can use
opti.optimize(Foo::objective,NULL);
but I do not want to have a static member. Is it possible to create an object of type Foo and give it to opti.optimize?
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Jul 20, 2013
Say you had:
class Foo{
public:
//...
void funky();
[Code] .....
Would each instance of Foo create a new counter variable, or would it remain the same for all of them, i.e. baz.funky() would always use the same counter variable? What if the class was a template?
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Sep 4, 2012
I am trying to use 'this' pointer but i am confused why 'this' pointer is not available for static member functions.
Code:
#include <iostream>
#include <fstream>
#include <stdlib.h>
using namespace std;
const int MAX = 20;
const int MAXPTR = 100;
class name {
private :
char fname[MAX], mname[MAX], lname[MAX];
[code].....
I am using GNU GCC Compiler via Code::Block
Error : 'this' is unavailable for static member functions
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Nov 29, 2012
The below code compiles without error using VS 2012 but with g++ 4.1.2 I get this error:
Code:
main.cpp: In function 'int main(int, char**)':
main.cpp:37: error: no matching function for call to 'StringHelper::stringToNumeric(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'
Here is the code:
#include <string>
#include "boost/lexical_cast.hpp"
using boost::lexical_cast;
using boost::bad_lexical_cast;
class StringHelper {
[Code] ....
This is part of a larger program so in reality StringHelper has more static functions but this example does produce the error the same as the code when in the larger program.
To get it to compile under g++ I had to assign the return value from substr() to a string and pass that string to stringToNumeric. Why do I have to do this for g++ and not VS? Do I have something wrong with my template function that g++ is calling out and VS is not?
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Aug 22, 2014
Have following code:
class Program
{
static void Main(string[] args)
{
[Code]....
My question according to what i just wrote:
1. Is that mean that Do() is only available for use by Dog itself because Dog is 'oryginal' Dog, and if i create new dogs - instances of oryginal Dog (dog1, dog2 ...) they cant access because Do is only available fo 'oryginal' one? Is that correct thinking?
2. If i would want to have something common (e.g value) for all dogs is that good way to create static field/method for Dog instead of non-static once then all instances of Dog would access Dog static member to get/change it? Just stupid example: static method GetAmountOfLegs() which return 4 Then all instances can take/call that value from Dog. Is that correct thinking?
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Apr 25, 2013
I am doing fixed point implementation in c++ which is done by the following code
#ifndef __fixed_point_header_h__
#define __fixed_point_header_h__
#include <boost/assert.hpp>
#include <boost/static_assert.hpp>
#include <boost/operators.hpp>
#include <limits>
[Code] ....
I am getting the error ambiguous overload for âoperator<â in âbeta < ((-5.0e-1) * pi)â
I know the problem the static member function cannot access the members and objects of structs. am i right?
and how to solve this problem, do i need to implement the cossin_cordic function as a non member function.
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Jun 25, 2013
Here's the definition of my struct:
struct Speaker {
static int numElem;
string name;
int number; // Phone
string topic;
float fee;
};
// IN main() FUNCTION
Speaker s[10];
The goal is for numElem to keep track of how many of the 10 elements are in use. However, I'm not sure the proper way to access the element, if it's even possible.
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