Theres a class named "A" which has got a static function named "sfA".Now I instance an object of class A and call a method from A called "fA".
The method fA calls sfA. And now the issue is: i need the value of a member from the object which called fA respectivly sfA, inside sfA.Is there a smarter way to get the value of the member as to declare an new parameter for the sfA? sfA has to be static.
I have some code here where I try to declare a struct then pass it as a parameter into a function to do something to it:
Code:
struct _user {
char * initial[3];
int pos;
} user;
int initial_add (struct user * initial_list, int initials, char * buffer) {
[Code] ...
I get the error :
server2.c:15: warning: "struct user" declared inside parameter list
server2.c:15: warning: its scope is only this definition or declaration, which is probably not what you want
[Code] ....
Basically, I need to set a variable outside of the constructor and make it accessible to the entire class.
It would need to work something like this:
#include <iostream>
#include <string>
template <typename MT> class CallbackFunction
{
[Code].....
i am trying to describe the unusual situation where you declare a class member function with this format:
bool class::function_name(void) const
Specifically where the 'const' follows the parameter list. It is my understanding this is a very useful way of ensuring that whatever code you put in the function definition cannot change any data members of its class.
However I have recently read that this form of declaration should not be used as it leads to less optimized and slower code. Is this correct?
I'm attempting to make a matrix class, and so far I've made a member that can make a vector of vectors, but I'm not sure how to go about resizing the vectors if need be.
EX: resizeArray(3,3) should return a 3x3 vector.
Also, for some reason when I call my default member, matrix(), I get an error that says.. "Request for member numrows in myMatrix, which is of type matrix<int>[][]"
#include <iostream>
#include <vector>
using namespace std;
[Code].....
In my project, GreedyKnap::calKnap(int nItem, int nCapacity, float fWeights, float fProfits);
This function include two array member pass as parameter. how can i do this?
I am not a C programmer (or a programmer at all). I am just a hobbyist who writes random code (i.e.: ignorant).C is not my area, and I my experience with it is quite LIMITED!Today, I found out that if I need to get "square root" in C I will be in trouble if I depend solely on the compiler..Is it possible to make the compiler to generate smarter code for this (quite trivial code):
Code:
void intprime_c(unsigned long* fprimes, unsigned long count)
{
unsigned long divc = 3;
unsigned long num = 2;
unsigned long sqr;
unsigned long pfound = 0;
}
[code]...
By "without ugly hacks" I mean using already existing code that came with GCC. Because the others did not need ugly hacks to perform better (it is all about being fair).To compute the "square root" in x86 one just need 3 instructions:
fild
fsqrt
fistp
But the compiler is generating a call to a "fsqrt" function and wasting a lot of time by doing this. If not, then why is it taking so long? Is it something wrong in my code (at least the output was verified to be the correct)?
Time taken to get the first 2500000 primes (x86_64):
Assembly = 72.400s (human written, unoptimized, coder level: newbie (i.e.: ignorant))
pascal = 75.200s (written by the same person)
C (fsqrt) = 83.600s (written by the same person)
C (sqrt) = 85.900s (written by the same person)
If it matters, I compiled the C code with this command: gcc -O2 -fno-omit-frame-pointer -fPIC -c ./prime.
My errors are at the end of the program in two function calls within the definition of the InsertByValue function. g++ does not seem to recognize NumArray as a valid parameter.
#include <iostream>
#include <assert.h>
using namespace std;
const int CAPACITY = 20;
/* Displays the content of an int array, both the array and the size of array will be passed as parameters to the function
@param array: gives the array to be displayed
@param array_size: gives the number of elements in the array */
void DisplayArray (int array[], int array_size);
[Code] ....
I am developing new project in Qt with existing MFC project . SO in MFC I have a function which uses SYSTEMTime and return CString.
example
CString getTimestampString( void )
{
SYSTEMTIME systemTime;
CString datestr;
[Code]....
PS -> I cant able to make any changes in lib_know as this library is being used by many other projects..
I get the following error in XCode whenever I try to access the member I created 'randomGen' in a separate class in a different header file. I have made sure to include the header file and have tried to access it through an object.
This is the code I enter when trying to access the method from randomiser.h in main.cpp. It is also an overloaded function with doubles and integers:
RandomG randomiser;
randomiser.randomGen(); // 'Call to member function 'randomGen' is ambiguous'
This is the code inside randomiser.h:
#include <string>
#include <iostream>
using std::string;
using std::cout;
using std::endl;
class RandomG {
[Code] ....
This is the error inside xcode: [URL] ....
I have tried seperating the code for the functions in another class (main.cpp) and then running and it seems to works, so I'm not sure why I can't put everything in the .h file and then access it?
I would like it in a seperate file so it doesn't clutter my main. I am writing a game with SDL so that might be confusing and I would like the window to have a random title and other random properties, so it would be easier to use a function.
How to declare functions in C++
View 1 Replies View RelatedI remember that the syntax exists I just don't remember what it is.I want to write a conditional function () prior to main (). in that function I'm using a variable that isn't introduced until main (). How do I let C know that I will be int'ng this function prior to the point where it is going to be accessed so that it doesn't freak out? alternatively is it possible to int the variable in both main() and my conditional function so that it exists? I imagine this would cause an issue because I would essentially be int'ng it twice.
I've done the cursory google searches however I don't think I'm using the correct keywords to get the results I'm looking for. If necessary I would be more than happy to post the code it's just a simple 40 line homework assignment.
I have this class with template:
template<template<class, class> class ContainerType>
class Movie {
public:
typedef ContainerType<Actor*, std::allocator<Actor*> > Container;
and i have a member func to find actor in movie according to actor id:
const Actor* findActor(int id) const {
typename Container::iterator it;
Actor* p(NULL);
it=actors.begin();
std::for_each(it,actors.end(),(*it)->getId()==id?p=*it:0);
if (p==*actors.end()) return NULL;
return p;
}
I receive error that no match for operator= in it.
How to declare correct iterator ?the type of actors is Container..
How i can declare a bit string in C++ .....
View 9 Replies View RelatedCan you declare a stack globally?
Code:
stack< int > stk;
It has been a few years since I have had to do this, but I need to declare a method in my base class, but produce no code for it. Then when this library is used by my second project I will derive a class from this base class and put the code into it there. How is this possible? I used to know how but do not remember how now.
The library is a static library designed for linking with both 32bit and 64bit Windows applications to handle a lot of the tedious stuff with Windows programming. The method in question handles specific command inputs. However, since each program that uses this library will have different uses for these commands, I want to leave it up to the user to code their own handling, but require it to be coded in the derived class.
is it possible to don't declare an object for a class and use the function of this class ? i saw a code use this but i cannot find it again .
View 7 Replies View Relateddecalration won't allocate storage, while definition will. This is a test program:
#include <iostream>
using namespace std;
extern int ei;
int i;
[Code].....
Others are all fine in this program except ei.
compiler error: undefined reference to ei.
I understand ei is only declared so there is no memory address, but when I do ei=1, then ei completed it's definition, why still cannot use pei to get it's address?
How to declare variable for all void() as I have another void s in my C++ program. I want to have a variable that can use for all the void and not only in a simple void.Is it possible?
View 17 Replies View RelatedI write these code in 2 different ways and I get the same result. I just want to make sure that they both are for declare a pointer using "auto"
The first one:
int varName = 10;
auto var1 = &varName;
cout << var1 << endl; //prints, varName address
cout << *var1 << endl; //prints, varName value
The second one:
int varName = 10;
auto *var2 = &varName;
cout << var2 << endl; //prints, varName address
cout << *var2 << endl; //prints, varName value
It doesn't matter if I put dereference operator or not, I still get the same result. I just want to make sure that var1 and var2 are both a pointer.
How can I forward declare an inner class?
I currently have this:
Code:
class Enigma
{
public:
Enigma()=delete;
Enigma(char r1,char r2,char r3,char r4, char r5, char r6, char r7, char r8, char r9, char r10);
~Enigma(){delete[] R;}
Enigma(const Enigma& rhs)=delete;
Enigma& operator=(const Enigma& rhs)=delete;
[Code]...
I'd like to be able to define Rotor outside of Enigma, but the compiler complains about incomplete types.
What is the purpose to declare constructor as protected?
View 13 Replies View RelatedI suspect that C++11 would make it possible to declare high rank vectors such as Code: int N = 15; // chosen arbitrary rank vector<vector<vector<...<vector<double>>>>..> vec; // N layers of nested vectors Is there a way to declare such a vector of rank N (given a fixed integer rank N)?
Heuristically I would like to write the declaration like this: Code:
vector<double> A;
vector<A> vec[0];
for(int i=1; i<N; i++)
{
vector<vec[i-1]> vec[i];
} Is there a way to use the new variadic templates to make this work?
I'm building a box to take in several arrays of different lengths. one group happens every 10 seconds. one of them happens every 5 seconds. this is from a weather station.
10 sec
subgroupA[14]
subgroupB[24]
subgroupC[17]
subgroupD[12]
subgroupE[34]
5 sec
subgroupC[17]
I plan to retransmit them, substantially unchanged at a lesser rate to save radio power over a serial data link. buried in groupD, I want to change a few chars before retransmit.
I don't want to go to the trouble of doing a structure for each of them since most will be resent unchanged. some entries are chars, some are decimal, some are a mix. I guess it might be convenient to further define groupD, maybe not.
what is the best way to declare the group? I want them to be contiguous since that's how they will end up in the tx buffer. Each subgroup has its own checksum, so I planned it this way to make checksum more convenient.
I want to declare a global array and then use it in a few functions. When I want to assign any number to that array I face with this error:
Code:
a.c:11:6: error: expected expression before ']' token
n[]={1,2,3,4,5};
^
The code is:
#include <stdio.h>
int n[5]; // I need to define the array here to be global
int main () {
n[]={1,2,3,4,5};
[Code] .....