Use this tag for questions related to the 'using' keyword in C++.
Questions tagged [using-declaration]
164 questions
3
votes
1 answer
Using namespace inside decltype
I have a function that looks more or less like this:
template auto f(C const& c) -> decltype(begin(c)){
using std::begin;
return begin(c);
}
The body of the function exploits the "using and use" idiom and
thanks to the decltype,…
alfC
- 14,261
- 4
- 67
- 118
3
votes
1 answer
What's the differences between `int*[1]` and `int(*)[1]`?
using T1 = int*[1];
using T2 = int(*)[1];
T1 t1;
T2 t2;
t1[0] = 0; // ok
t2[0] = 0; // error : array type 'int [1]' is not assignable
t2 = t1; // error : array type 'int [1]' is not assignable
t2 = &t1; // error : array type 'int [1]'…
szxwpmj
- 465
- 2
- 10
3
votes
2 answers
Why can an (irrelevant) using declaration reconcile overload ambiguity with Argument-Dependent Lookup?
This is a follow up of the question here on function overload with Argument-Dependent Lookup (ADL). I wanted to check my understanding of the rules under these circumstances so I wrote some test code.
First, there is no swap for HasPtr class in std,…
user5280911
- 723
- 1
- 8
- 21
3
votes
1 answer
Using declaration contains unexpanded parameter pack
How do I get this code to compile?
struct type1 {};
struct type2 {};
struct handler1
{
void handle(type1){}
};
struct handler2
{
void handle(type2){}
};
template
struct TheHandler : Handlers...
{
using…
Nikola Smiljanić
- 26,745
- 6
- 48
- 60
3
votes
3 answers
Is it possible to "bundle" template parameters in C++?
Is there a way to "bundle" template parameters together to avoid repetition?
I have several classes and functions that all use the same three template parameters. It is not unusual to have a function that uses each class/function once. The…
Zack
- 6,232
- 8
- 38
- 68
3
votes
1 answer
Q_ENUMS and using declarations do not work together
Consider the following class definition:
// exported.hpp
#include
class Exported: public QObject {
Q_OBJECT
public:
using QObject::QObject;
enum class FOO { BAR };
Q_ENUM(FOO)
};
And the following main file:
//…
skypjack
- 49,335
- 19
- 95
- 187
3
votes
0 answers
Name conflicts not detected when using aliases
This is a follow up to this question. Consider the following example:
#include
namespace MyProject {
class string {
public: string() { std::cout << "Callin string constructor" << std::endl; }
};
}
namespace Other {
…
swahnee
- 2,661
- 2
- 24
- 34
3
votes
1 answer
C++ using declaration and argument dependent lookup
Is the code below valid C++98 or does it require a newer version of the C++ standard?
namespace basic
{
void f(int) {}
}
namespace lib
{
template
void g(T1 x1, T2 x2)
{
using basic::f; // pull in function f for basic…
Jesper Schmidt
- 31
- 2
3
votes
2 answers
How does unqualified name lookup work when using using-declarations?
Is this ill-formed or well-formed according to the c++ standard?
namespace M { struct i {}; }
namespace N { static int i = 1; }
using M::i;
using N::i;
int main() { sizeof (i); }
Clang rejects it and GCC accepts it.
According to [namespace.udir-6]…
Supremum
- 542
- 7
- 23
3
votes
1 answer
Redefinition inconsistency in clang between struct and int
The following program gives no error when compiling with clang:
namespace X {
struct i {};
}
namespace Y {
using X::i;
struct i {};
}
int main() {}
Let's use int instead of struct, then we get:
namespace X {
int i;
}
namespace Y…
Supremum
- 542
- 7
- 23
3
votes
1 answer
Assignment operator overloads have similar conversions (only in VS)
I have a class hierarchy with three classes (A, B and C). A and B are base-classes, parametrized with the derived Type. Class C is derived from both, A and B.
The class B provides an assignment operator for objects of type A and class C inherits…
spraetor
- 441
- 4
- 13
3
votes
2 answers
What the author is trying to say in GotW #53?
This pseudo-code was obtained from GotW #53 under the subtitle "A Not-So-Good Long-Term Solution". I've been trying to understand for a few hours already what the author is saying, specially in relation to the comment starting with "// error:…
Wake up Brazil
- 3,421
- 12
- 19
3
votes
2 answers
Inheriting parent assignment operator when child's is implicitly deleted
In GCC 4.6, it is possible to inherit a parent's assignment operators even when the child's assignment operators are implicitly deleted due to a move constructor. In later versions of GCC (as well as Clang), this is no longer possible. What is the…
rcv
- 6,078
- 9
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- 63
3
votes
1 answer
Does a using-declaration only import overloads declared above the using-declaration?
For example, GCC and clang both fail to compile the following code:
struct S {};
namespace N
{
void g(S);
}
using N::g;
namespace N
{
void g(int);
}
int main()
{
g(0);
}
with the error:
test.cpp: In function 'int…
HighCommander4
- 50,428
- 24
- 122
- 194
2
votes
4 answers
How to use 'Using' keyword in ASP.NET page without code behind
I want to include some namespaces with their classes in my asp.net application. It is possible with using keyword ?
I have this:
<%
…
Snake Eyes
- 16,287
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