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POAcademic question: typename
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  1. POAcademic question: typename
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    copied!<blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/642229/why-do-i-need-to-use-typedef-typename-in-g-but-not-vs">Why do I need to use typedef typename in g++ but not VS?</a> </p> </blockquote> <p>Hi, recently I accounted with a "simple problem" of porting code from VC++ to gcc/intel. The code is compiles w/o error on VC++:</p> <pre><code>#include &lt;vector&gt; using std::vector; template &lt;class T&gt; void test_vec( std::vector&lt;T&gt; &amp;vec) { typedef std::vector&lt;T&gt; M; /*==&gt; add here typename*/ M::iterator ib=vec.begin(),ie=vec.end(); }; int main() { vector&lt;double&gt; x(100, 10); test_vec&lt;double&gt;(x); return 0; } </code></pre> <p>then with g++ we have some unclear errors:</p> <pre><code> g++ t.cpp t.cpp: In function 'void test_vec(std::vector&lt;T, std::allocator&lt;_CharT&gt; &gt;&amp;)': t.cpp:13: error: expected `;' before 'ie' t.cpp: In function 'void test_vec(std::vector&lt;T, std::allocator&lt;_CharT&gt; &gt;&amp;) [with T = double]': t.cpp:18: instantiated from here t.cpp:12: error: dependent-name 'std::M::iterator' is parsed as a non-type, but instantiation yields a type t.cpp:12: note: say 'typename std::M::iterator' if a type is meant </code></pre> <p>If we add <strong>typename</strong> before iterator the code will compile w/o pb.</p> <p>If it is possible to make a compiler which can understand the code written in the more "natural way", then for me is unclear why we should add typename? Which rules of "C++ standards"(if there are some) will be broken if we allow all compilers to use without "typename"?</p> <p>kind regards Arman.</p>
 

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