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POprivate and public operator overloading
 

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  1. POprivate and public operator overloading
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    <p>I tried to implement the method of Horner and faced a problem:</p> <pre><code>root@host:~# cat | g++ -x c++ -std=gnu++11 - &amp;&amp; ./a.out #include &lt;iostream&gt; #include &lt;iomanip&gt; #include &lt;iterator&gt; #include &lt;vector&gt; #include &lt;numeric&gt; #include &lt;algorithm&gt; #include &lt;random&gt; #include &lt;chrono&gt; #include &lt;cstdlib&gt; template&lt; typename F &gt; class horner { public : typedef std::vector&lt; F &gt; V; horner(F const &amp; x_, V const &amp; c_) : x(x_) , c(c_) , y(0.0L) { ; } operator F const () const { return std::accumulate(c.rbegin(), c.rend(), *this).y; } private : friend horner std::accumulate&lt; typename V::const_reverse_iterator, horner &gt;(typename V::const_reverse_iterator, typename V::const_reverse_iterator, horner); void operator = (F const &amp; rhs) { y = rhs; } operator F () { y *= x; return y; } F const &amp; x; V const &amp; c; F y; }; #define N_COEFF_PARABOLA 3 int main() { typedef double F; typedef typename horner&lt; F &gt;::V V; V c; unsigned seed(std::chrono::system_clock::now().time_since_epoch().count()); std::cout &lt;&lt; "seed = 0x" &lt;&lt; std::uppercase &lt;&lt; std::hex &lt;&lt; std::setfill('0') &lt;&lt; std::setw(sizeof(seed) * 2) &lt;&lt; seed &lt;&lt; std::endl; std::mt19937 generator(seed); std::generate_n(std::back_inserter(c), N_COEFF_PARABOLA, generator); std::cout &lt;&lt; "coefficients: "; std::copy(c.begin(), c.end(), std::ostream_iterator&lt; F &gt;(std::cout, " ")); std::cout &lt;&lt; ';' &lt;&lt; std::endl; F const x(generator()); F const y(horner&lt; F &gt;(x, c)); std::cout &lt;&lt; "y(" &lt;&lt; x &lt;&lt; ") = " &lt;&lt; y &lt;&lt; std::endl; // naive F xx(1.0L); F yy(0.0L); for (typename V::size_type i(0); i &lt; c.size(); ++i) { yy += c[i] * xx; xx *= x; } std::cout &lt;&lt; "y'(" &lt;&lt; x &lt;&lt; ") = " &lt;&lt; yy &lt;&lt; std::endl; return EXIT_SUCCESS; } // press ^D &lt;stdin&gt;: In function ‘int main()’: &lt;stdin&gt;:39:5: error: ‘horner&lt;F&gt;::operator F() [with F = double]’ is private &lt;stdin&gt;:71:32: error: within this context root@host:~# </code></pre> <p>In my view the problem should not arise, since <code>main()</code> only sees <code>operator F const &amp; () const</code> version of the type conversion operator. But it is.</p> <p>What is the reason of the error?</p>
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    1. USXeo
    1. USOrient
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      1. POprivate and public operator overloading
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      1. VTUpMod
    1. COOverload resolution does not care about access specifiers.
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      1. USR. Martinho Fernandes
    2. COIndeed, because they're not a part of a method signature.
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      1. POprivate and public operator overloading
      1. USYam Marcovic
 

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