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POMissing Template Arguments
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  1. POMissing Template Arguments
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    copied!<p>This is part of a homework assignment, but I've reduced the problem as far as possible. The code presented doesn't really do anything, just create some objects, so I am down to pure language issues.</p> <p>I think my question is: Is it possible for a template class to create another class of the same template type?</p> <p>The assignment is to have a main.cc as following:</p> <pre class="lang-cpp prettyprint-override"><code>#include "linkedlist.hh" int main() { LinkedList&lt;int&gt; aList; ListIterator elements = aList.iterator(); // if commented out, then no error } </code></pre> <p>I have the following for linkedlist.hh:</p> <pre class="lang-cpp prettyprint-override"><code>template &lt;typename T&gt; class LinkedList; template &lt;typename T&gt; class ListIterator; template &lt;typename T&gt; class LinkedList { public: ListIterator&lt;T&gt; iterator(); }; template &lt;typename T&gt; ListIterator&lt;T&gt; LinkedList&lt;T&gt;::iterator() { return new ListIterator&lt;T&gt;; } template &lt;typename T&gt; class ListIterator { }; </code></pre> <p>Which give the following error with g++-4.6:</p> <pre><code>main.cc: In function ‘int main()’: main.cc:6:18: error: missing template arguments before ‘elements’ main.cc:6:18: error: expected ‘;’ before ‘elements’ </code></pre> <p>And a similar error with clang++-2.9:</p> <pre><code>main.cc:6:5: error: cannot refer to class template 'ListIterator' without a template argument list ListIterator elements = list.iterator(); ^ In file included from main.cc:1: ./linkedlist.hh:16:11: note: template is declared here class ListIterator { </code></pre> <hr> <h2>UPDATE: Yes if I could change main.cc, then I could do the following, but I don't think that is what the assignment is.</h2> <p>main.cc</p> <pre class="lang-cpp prettyprint-override"><code>#include "linkedlist.hh" int main() { LinkedList&lt;int&gt; aList; ListIterator&lt;int&gt; elements = aList.iterator(); } </code></pre> <p>and linkedlist.hh</p> <pre class="lang-cpp prettyprint-override"><code>template &lt;typename T&gt; class LinkedList; template &lt;typename T&gt; class ListIterator; template &lt;typename T&gt; class LinkedList { public: ListIterator&lt;T&gt; iterator(); }; template &lt;typename T&gt; ListIterator&lt;T&gt; LinkedList&lt;T&gt;::iterator() { ListIterator&lt;T&gt; anIterator; return anIterator; } template &lt;typename T&gt; class ListIterator { }; </code></pre>
 

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