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namespace CounterNameSpace {
int upperbound;
int lowerbound;
using namespace NS;//Error
}
namespace NS {
int i;
}
// ...
namespace NS {
int j;
}
In the above case it shows an error . error C2871: 'NS' : a namespace with this name does not exist I know if i define NS before counternamespace problem will be solved . But just want to know whether any thing like forward declaration of namespace exist in c++ or not .So that the above problem will be resolved without defining NS before counternamespace . please help .
270
There is no forward declaration of namespace. You can forward declare a function.
In computer programming, a forward declaration is a declaration of an identifier (denoting an entity such as a type, a variable, a constant, or a function) for which the programmer has not yet given a complete definition.
In C++, Forward declarations are usually used for Classes. In this, the class is pre-defined before its use so that it can be called and used by other classes that are defined before this. Example: // Forward Declaration class A class A; // Definition of class A class A{ // Body };
Typically, you declare a namespace in a header file. If your function implementations are in a separate file, then qualify the function names, as in this example. A namespace can be declared in multiple blocks in a single file, and in multiple files.
Nothing says a namespace needs all of its contents right away:
namespace NS {}
namespace CounterNameSpace {
int upperbound;
int lowerbound;
using namespace NS;
}
namespace NS {
int i;
}
However, this might not do what you want. You still won't be able to use any of the types in that namespace until you've declared them.
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