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POfriend of specialized template class (C++)
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  1. POfriend of specialized template class (C++)
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    copied!<pre><code>#include &lt;iostream&gt; using namespace std; template &lt;typename T&gt; class test { T y; public: test(T k) : y(k) {} friend int a(T&amp; x); }; template &lt;typename T&gt; int a(T&amp; x) { cout &lt;&lt; x.y; return 9; } template &lt;&gt; class test&lt;int&gt; { int y; public: test(int k) : y(k) {} friend int a(int&amp; x); }; template &lt;&gt; int a&lt;int&gt;(int&amp; x) { cout &lt;&lt; "4"; return 0; } int main(int argc, char* argv[]) { test&lt;int&gt; z(3); a(z); return 0; } </code></pre> <p>I want to make a friend class of test class (in a real case, it was a operator&lt;&lt; of ofstream). But I have no idea how to define template friend function of specialized class.</p> <p>Besides, the code above shows this compile error message;</p> <blockquote> <p>error C2248: 'test::y' : cannot access private member declared in class 'test'</p> </blockquote> <p><strong>Question added;</strong></p> <p>Aaron McDaid works fine for me, but I was trying to overload operator&lt;&lt; of ofstream class. </p> <pre><code>friend ofstream&amp; operator&lt;&lt; &lt;test&lt;int&gt;&gt; (ofstream&amp; os, const test&lt;int&gt;&amp; t); </code></pre> <p>I added code above to test class and</p> <pre><code>template&lt;&gt; ofstream&amp; operator&lt;&lt; &lt;test&lt;int&gt; &gt; (ofstream&amp; os, const test&lt;int&gt;&amp; t) { os &lt;&lt; t.y; return os; } </code></pre> <p>used code above. But it looks like I cannot use os &lt;&lt; t.y (which is <em>int</em>) I don't understand why this happens. The error message is</p> <blockquote> <p>error C2027: use of undefined type 'std::basic_ofstream&lt;_Elem,_Traits>'</p> </blockquote>
 

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