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POC++ templated functor in lambda expression
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  1. POC++ templated functor in lambda expression
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    copied!<p>This first piece has been solved by Eric's comments below but has led onto a secondary issue that I describe after the horizontal rule. Thanks Eric!</p> <p>I'm trying to pass a functor that is a templated class to the create_thread method of boost thread_group class along with two parameters to the functor. However I can't seem to get beyond my current compile error. With the below code:</p> <pre><code>#include &lt;boost/lambda/lambda.hpp&gt; #include &lt;boost/lambda/bind.hpp&gt; #include &lt;boost/thread.hpp&gt; #include &lt;vector&gt; using namespace boost::lambda; using namespace std; namespace bl = boost::lambda; template&lt;typename ftor, typename data&gt; class Foo { public: explicit Foo() { } void doFtor () { _threads.create_thread(bind(&amp;Foo&lt;ftor, data&gt;::_ftor, _list.begin(), _list.end())); //_threads.create_thread(bind(_ftor, _list.begin(), _list.end())); _threads.join_all(); } private: boost::thread_group _threads; ftor _ftor; vector&lt;data&gt; _list; }; template&lt;typename data&gt; class Ftor { public: //template &lt;class Args&gt; struct sig { typedef void type; } explicit Ftor () {} void operator() (typename vector&lt;data&gt;::iterator &amp;startItr, typename vector&lt;data&gt;::iterator &amp;endItr) { for_each(startItr, endItr, cout &lt;&lt; bl::_1 &lt;&lt; constant(".")); } } </code></pre> <p>I also tried typedef-ing 'type' as I thought my problem might have something to do with the Sig Template as the functor itself is templated. </p> <p>The error I am getting is:</p> <pre><code>error: no matching function for call to ‘boost::lambda::function_adaptor&lt;Ftor&lt;int&gt; Foo&lt;Ftor&lt;int&gt;, int&gt;::*&gt;::apply(Ftor&lt;int&gt; Foo&lt;Ftor&lt;int&gt;, int&gt;::* const&amp;, const __gnu_cxx::__normal_iterator&lt;int*, std::vector&lt;int, std::allocator&lt;int&gt;&gt; &gt;&amp;, const __gnu_cxx::__normal_iterator&lt;int*, std::vector&lt;int, std::allocator&lt;int&gt; &gt; &gt;&amp;)’ </code></pre> <p>with a bunch of preamble beforehand. </p> <p>Thanks in advance for any help!</p> <hr> <p>Okay I've modified the code taking in Eric's suggestions below resulting in the following code:</p> <pre><code>#include &lt;boost/lambda/lambda.hpp&gt; #include &lt;boost/lambda/bind.hpp&gt; #include &lt;boost/thread.hpp&gt; #include &lt;vector&gt; using namespace boost::lambda; using namespace std; namespace bl = boost::lambda; template&lt;typename ftor, typename data&gt; class Foo { public: explicit Foo() { } void doFtor () { _threads.create_thread(bl::bind(boost::ref(_ftor), _list.begin(), _list.end())); _threads.join_all(); } private: boost::thread_group _threads; ftor _ftor; vector&lt;data&gt; _list; }; template&lt;typename data&gt; class Ftor { public: typedef void result_type; explicit Ftor () {} result_type operator() (typename vector&lt;data&gt;::iterator &amp;startItr, typename vector&lt;data&gt;::iterator &amp;endItr) { for_each(startItr, endItr, cout &lt;&lt; bl::_1 &lt;&lt; constant(".")); return ; } }; </code></pre> <p>However this results in another compile error:</p> <pre><code>/usr/local/include/boost/lambda/detail/function_adaptors.hpp:45: error: no match for call to ‘(Ftor&lt;int&gt;) (const __gnu_cxx::__normal_iterator&lt;int*, std::vector&lt;int, std::allocator&lt;int&gt; &gt; &gt;&amp;, const __gnu_cxx::__normal_iterator&lt;int*, std::vector&lt;int, std::allocator&lt;int&gt; &gt; &gt;&amp;)’ ftor.h:41: note: candidates are: void Ftor&lt;data&gt;::operator()(typename std::vector&lt;data, std::allocator&lt;_CharT&gt; &gt;::iterator&amp;, typename std::vector&lt;data, std::allocator&lt;_CharT&gt; &gt;::iterator&amp;) [with data = int] /usr/local/include/boost/lambda/detail/function_adaptors.hpp:45: error: return-statement with a value, in function returning 'void' </code></pre> <p>It seems having defined void as a result_type it is now expecting the operator() to return something. I tried returning result_type from within the function but this also generated errors. Any ideas?</p>
 

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