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POHow to allow template function to have friend(-like) access?
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  1. POHow to allow template function to have friend(-like) access?
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    copied!<p>How does one modify the following code to allow template function <code>ask_runUI()</code> to use <code>s_EOF</code> without making <code>s_EOF</code> public?</p> <pre><code>#include &lt;string&gt; #include &lt;iostream&gt; #include &lt;sstream&gt; #include &lt;vector&gt; class AskBase { protected: std::string m_prompt; std::string m_answer; virtual bool validate(std::string a_response) = 0; public: AskBase(std::string a_prompt):m_prompt(a_prompt){} std::string prompt(){return m_prompt;} std::string answer(){return m_answer;} static int const s_EOF = -99; static int const s_BACKUP = -1; static int const s_OK = 1; int ask_user(); }; template&lt;typename T&gt; class Ask : public AskBase{ public: Ask(std::string a_prompt):AskBase(a_prompt){} bool validate(std::string a_response); }; template&lt;&gt; bool Ask&lt;std::string&gt;::validate(std::string a_response){return true;} template&lt;&gt; bool Ask&lt;int&gt;::validate(std::string a_response){int intAnswer; return (std::stringstream(a_response) &gt;&gt; intAnswer);} int AskBase::ask_user(){ for(;;){ std::cout &lt;&lt; "Enter " &lt;&lt; m_prompt; std::string response; getline(std::cin, response); if (std::cin.eof()) return s_EOF; else if (response == "^") return s_BACKUP; else if (validate(response)){ m_answer = response; return s_OK; } } return s_EOF; } template&lt;typename T&gt; int ask_runUI(T&amp; a_ui){ int status = AskBase::s_OK; for (typename T::iterator ii=a_ui.begin(); status!=AskBase::s_EOF &amp;&amp; ii!=a_ui.end(); ii+=((status==AskBase::s_BACKUP)?((ii==a_ui.begin())?0:-1):1) status = (*ii)-&gt;ask_user(); return (status == AskBase::s_OK); } int main(){ std::vector&lt;AskBase*&gt; ui; ui.push_back(new Ask&lt;std::string&gt;("your name: ")); ui.push_back(new Ask&lt;int&gt;("your age: ")); if (ask_runUI(ui)) for (std::vector&lt;AskBase*&gt;::iterator ii=ui.begin(); ii!=ui.end(); ++ii) std::cout &lt;&lt; (*ii)-&gt;prompt() &lt;&lt; (*ii)-&gt;answer() &lt;&lt; std::endl; else std::cout &lt;&lt; "\nEOF\n"; } </code></pre>
 

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