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POWhy can I not use the namespace directive in c++ struct?
 

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  1. POWhy can I not use the namespace directive in c++ struct?
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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/4362831/scoped-using-directive-within-a-struct-class-declaration">Scoped using-directive within a struct/class declaration?</a><br> <a href="https://stackoverflow.com/questions/6326805/why-using-namespace-x-is-not-allowed-inside-class-struct-level">Why &ldquo;using namespace X;&rdquo; is not allowed inside class/struct level?</a> </p> </blockquote> <p>I would like to introduce only std::string into structure. Why is the below considered illegal?</p> <pre><code>#include &lt;iostream&gt; #include &lt;string&gt; struct Father { using std::string; string sons[20]; string daughters[20]; }; </code></pre> <p>But oddly enough, i can do the following the in a function</p> <pre><code>int main() { using std::string; } </code></pre> <p>Update: C++ uses the same keyword with different semantics. </p> <p>c++ uses the keyword "using" to introduce a data member or function from the base class into the current class. Thus when i wrote using std::string inside a struct declaration, compiler is assuming that i am trying to introduce a member from a base class std. But std is not a base class, rather it is a namespace. Thus </p> <pre><code>struct A { int i; } struct B:A { using A::i; // legal using std::string// illegal, because ::std is not a class } </code></pre> <p>the same "using" keyword is also used to access a member of a particular namespace.</p> <p>So, i am guessing compiler decides the semantics of "using" based on where it is declared.</p>
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      1. USStuart Golodetz
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    1. COPlease **do not** remove the automatically inserted "possible duplicate" link when you edit the question. I understand that you updated in order to explain why you think it's *not* a duplicate of the suggested question, and that's perfectly acceptable/encouraged behavior. But you should either let your edits bump up the question and attract re-open votes from users who notice it in the list, or use the "flag" link to ask a moderator to examine and re-open it as per your updates. Removing the automatically inserted link is very strongly discouraged; the system will remove it upon reopening.
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      1. USCody Gray
    2. CO(If removing it was an accident in this case—i.e., your edits collided in time—then I apologize for the harsh-sounding tone. Just take it as good advice for the future! :-))
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