C++ :: Static Assert Not Allowed In Enums
Feb 13, 2014
I'm going from section 7.1 where it is stated that:
Standard wrote:A declaration occurs in a scope (3.3); the scope rules are summarized in 3.4. A declaration that declares a function or defines a class, namespace, template, or function also has one or more scopes nested within it.
Jumping to section 3.3 we find that there exist block scope, function prototype scope, function scope, namespace scope, class scope, enumeration scope, and template parameter scope.
I find nothing that states that static_assert declarations cannot be used in any of those scopes, yet only block, function, class, and namespace scopes allow for it with clang.
static_assert(true, "");// namespace scope (good))
class X {
static_assert(true, "");// class scope (good))
[Code].....
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Mar 1, 2013
I have a function like this
void foo( int i) {
...
uint8_t buf[ i];
...
}
And I don't understand why the compiler is not complaining... I'm using g++ -c -g -Wall to compile ....
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Apr 19, 2013
Here is the code I have written so far. My problem is that when the second user enters its position the last user's position is wiped of the board. I want to know how I can hold that position and keep doing so until the game is finished. I thought that calling the previous function would do that (and you can see where I have put that into a comment) but it doesn't.
Code:
#include <iostream> //includes header file
using namespace std;
//function prototypes
void printLeftUpper(int i, int j);
void printMiddleUpper(int i, int j);
[Code] ....
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Aug 26, 2013
Assume this class:
class GenericTrafficLight {
public:
virtual enum LightState;
void setLightState(LightState newState) {
currentState = newState;
}
private:
LightState currentState;
};
And this deriving class:
class FuturisticTrafficLight : public GenericTrafficLight {
public:
enum LightState {
LIGHT_STATE_RED = 0,
LIGHT_STATE_YELLOW = 1,
LIGHT_STATE_CYAN = 2,
LIGHT_STATE_GREEN = 3
};
};
This yields this error: "C2911 (...) cannot be declared or defined in the current scope" in the deriving class's enum definition.
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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 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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Jul 22, 2013
#include<iostream>
#include<cstdio>
#include<list>
[Code]....
In the last line "graph.edge{x,y,w}" it says typename is not allowed? I have used nested class edge and pushing vertices and their weight in elist vector which is of type edge.
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May 8, 2013
I am trying to get a program to take two files and place them into a third file. I have searched all over this website looking for a solution and i can seem to find one.
My issue is that i keep getting an error 'incomplete type is not allowed' as well as 'no operator matches these ">>" these operands.'
#include<iostream>
#include<string>
#include <sstream>
using namespace std;
int main() {
string filename1;
[Code] .....
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Jul 19, 2012
So, I ran into the above error. I can't post the actual code, but here is the setup... I have four classes: A, B, C, and D.
A.hpp
Code:
class A {
public:
virtual void foo( D& bar );
[Code] .....
In A.cpp I implement foo and use bar in a similar manner as shown in class C. The difference here is that in A.cpp I also include the header for the D class. I am a bit confused why I can pass bar to B::foo() and that works fine, but if I try to access bar in C::foo, I have issues. Currently I am just including D.hpp in C.cpp.
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Jan 4, 2014
I had defined enums in a class like this:
Code:
class Enums {
public:
enum COLOURS {BLACK, GRAY, RED, ORANGE, YELLOW,
GREEN, BLUE, PURPLE, BROWN, PINK, WHITE};
}
But I don't want to use the enums inside of that class. I want to use it in the main file like this:
Code:
#include <iostream>
using namespace std;
void SetColor(const int COLOR) {
cout << COLOR << endl;
}
int main(int argc, char* argv[]) {
void SetColor(BLACK);
return 0;
}
Without getting a syntax error.
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Sep 30, 2014
I have an enum like:
Code:
typedef enum mac_type_e{
STATIC_MAC,
BLACKLIST_MAC
} mac_type_t; and I want to use this type in a structure that's declared like:
Code:
typedef struct lan_mac_s {
UINT16 lanmacid;
enum mac_type_t lan_mac_type_pp;// user mac type per port, 20 mac_type_t array, 0 = static, 1 = blacklisted now,
The compiler tells me:
Code:
incomplete type is not allowed
enum mac_type_t lan_mac_type_pp;// user mac type per port, 20 mac_type_t array, 0 = static, 1 = blacklisted
But if I remove the preceeding "enum" keyword, it compiles fine.
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Feb 15, 2013
this is my header file
#ifndef Header_H
#define Header_H
#include <iostream>
#include <string>
using namespace std;
class CurrentAccount{
[Code] ....
The problem i m facing now is the CurrentAccount class display is showing error inherited member is not allowed....
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May 26, 2014
When declare and assign an instance of a user-defined struct in a function. And the struct (theStruct) is not declared in the same header file as the function (theFunction). Like this:
files:
"A.h": declares the struct in a class (theClass)
"A.cpp": implements the struct
"B.h": declares the function
"B.cpp": implements the function, error here
I think making the instance (inst) a reference might solve this. But the instance is assigned to a return value from a function (returnFunc). Like:
void theFunction() {
...
theClass::theStruct inst = returnFunc(...);
//returnFunc() returns an instance of theStruct
//the error is at 'inst'
...
}
What do you think?
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Jul 19, 2014
I have made a datagrid in a WPF and added a button to add rows, here is the code for that:
this.itemListDataGrid.Items.Add(new TextBox());
Also, I have already got 3 colums in the datagrid pre-added by me, so when the rows are added I click on one to edit it and it comes up with error edit item not allowed.
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May 21, 2013
Code:
#include "..ObjectsObjects.h"
class Idle;
class Objects;
class Goods;
[Code].....
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Nov 24, 2013
[URL] ....
#include <iostream>
#include <vector>
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end()) {
} int main() {
f({}); }
prog.cpp:4:73: error: local variable ‘v’ may not appear in this context
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end())
Why is this not allowed? (I mean, what is the reasoning for defining the standard this way?)
In C++14/C++17 we will have a unified way to represent end iterators without an instance of the container, but currently I just have to hope my implementation accepts a default-constructed iterator as an end iterator.
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Dec 5, 2014
So I received an error of "type name is not allowed" and I don't know how to fix this.... Here is the code:
retrieveData(string Name, double wage, double hours, int exemptions, char Status);
dataCalculations(double wage, double hours, int exemptions, char Status, double grossPay, double ficaTax, double incomeTax, double netPay, double taxWithheld);
sendData(string Name, int ID, double hours, double wage, double ficaTax, double incomeTax, double grossPay, double netPay);
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Jun 16, 2013
Here is the pseudocode,
Code:
class myDX9Widget {
std::vector<Object*> m_vRenderObjects;
};
class Object {
};
class Lorry : public Object {
Activity *activity;
[Code] .....
Don't worry about the exact syntax here, I'd like to concentrate, on a conceptual level, why the line
lorry->Owner->m_vRenderObjects.push_back(pallet);
is not allowed
lorry is regarded as "Pointer to incomplete class"
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Sep 27, 2013
I am IT student and had a C++/C (oral + paper) exam today. One of the tasks was to write a 2D-Matrix (as the question said) class with following restrictions:
- No <string> header is allowed
- Only Dtor needs to be implemented
- No templates
- Following should be possible:
Code:
std::cout << mat1 + mat2 + "some randome string";
mat1 += mat2; So i did the following:
In Matrix.h i wrote: Code: Class Matrix{
int rows, cols;
char *arr[][];
[Code] .....
Now..this destructor made me loose some points since the Prof. said that it is not correct. The corrected version was:
Code:
Matrix::~Matrix(){
if(arr){
for(int i = 0; i < rows; i++){
for(int j = 0; j < cols; j++){
delete [] arr[i][j];
[Code] ....
Now, i agree on that error i made, but it is only in case we use the "new" keyword to reserve place dynamically for each string(for each char*). So this raised the question in my head about:
Since the following is allowed in C++
Code:
char* str1 = "hello";
char* str2 = "you";
arr[1][3] = str1;//arr[1][3] was initialized to "_" without new keyword
arr[6][0] = str2;//arr[6][0] was initialized to "_" without new keyword why would someone use the new keyword..
I mean like this:
Code:
arr[1][3] = new char*[sizeof("sometext1")+1];
arr[1][3] = "sometext1";
arr[6][0] = new char*[sizeof("sometext2")+1];
arr[6][0] = "sometextw";
What is happening internally in C++ in both the cases(with and without new keyword)?
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Sep 4, 2014
I'm trying figure out how Windows Firewall functions by experimenting with Bittorrent's add exception to windows firewall option, I deleted the entry from the Firewall options and also located that the regkeys are in HKLM/System/CurrentControlSet/Services/SharedAccess/Parameters/FirewwallPolicy but I can't figure out what registries are made when an application is added as an exception in the Windows Registry.
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Jul 28, 2013
C++ only allow addition and subtraction operation with pointer .why multiplication and division is not allowed? Then how to perform multiplication and division with pointer
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Mar 6, 2015
So I need to make a main function have no if/for/etc. statements so I need to move it to another function and call it in main. The problem is that it's a command line argument function so I'm confused on how it works. Here's an example:
Code:
#include <stdio.h>
int main(int argc, char* argv[])
{
printf("The program name %s", argv[0]);
if (argc == 2) {
printf("Argument supplied is %s", argv[1]); }
else if (argc > 2) {
printf("Too many arguments");}
else {
printf("One argument");}
}
How can i make this into two functions with main only declaring variables and calling other functions?
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Aug 1, 2014
Code:
class VAR_EXPORT VAR {
public:
};
VAR_EXPORT QDataStream &operator>>(QDataStream &p_stream, QSharedPointer<Data>& p_data)
[Code] ....
Above compile and build ok. But when i build another library that use the above, i was shown with all errors complaining operator << and >> definition of dllimport function not allowed
error C2491: 'operator >>' : definition of dllimport function not allowed
error C2491: 'operator <<' : definition of dllimport function not allowed
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Aug 5, 2013
Here is the code,
Code:
class A {
};
A& CreateObject() {
static A a;
return a;
} static A aa;
int main() {
return 0;
}
So is there any difference between a defined in CreateObject and aa?
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Oct 14, 2013
So, even though the virtual pointer is constant across objects of class why cant it be made as static. Why each derived instance is having the pointer to vtable.
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