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    CWG Issue 387</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="387"></A><H4>387.
  
Errors in example in 14.6.5
</H4>
<B>Section: </B>_N4868_.13.8.6&#160; [<A href="https://wg21.link/temp.inject">temp.inject</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD1
 &#160;&#160;&#160;

 <B>Submitter: </B>Aleksey Gurtovoy
 &#160;&#160;&#160;

 <B>Date: </B>27 Oct 2002<BR>


<P>[Voted into WP at March 2004 meeting.]</P>

<P>The example in _N4868_.13.8.6 [<A href="https://wg21.link/temp.inject#2">temp.inject</A>] paragraph 2
is incorrect:</P>
<PRE>
  template&lt;typename T&gt; class number {
      number(int);
      //...
      friend number gcd(number&amp; x, number&amp; y) { /* ... */ }
      //...
  };

  void g()
  {
      number&lt;double&gt; a(3), b(4);
      //...
      a = gcd(a,b);   // finds gcd because number&lt;double&gt; is an
                      // associated class, making gcd visible
                      // in its namespace (global scope)
      b = gcd(3,4);   // ill-formed; gcd is not visible
  }
</PRE>
<P>Regardless of the last statement ("b = gcd(3,4);"), the above code is
ill-formed:</P>

<P>  a) number's constructor is private;</P>
<P>  b) the definition of (non-void) friend 'gcd' function does not
contain a return statement.</P>

<P><B>Proposed resolution (April 2003):</B></P>

<P>
Replace the example in _N4868_.13.8.6 [<A href="https://wg21.link/temp.inject#2">temp.inject</A>] paragraph 2
</P>

<BLOCKQUOTE>
<PRE>
  template&lt;typename T&gt; class number {
          number(int);
          //...
          friend number gcd(number&amp; x, number&amp; y) { /* ... */ }
          //...
  };

  void g()
  {
          number&lt;double&gt; a(3), b(4);
          //...
          a = gcd(a,b);           //  finds  gcd  because  number&lt;double&gt;  is an
                                  //  associated class, making  gcd  visible
                                  //  in its namespace (global scope)
          b = gcd(3,4);           //  ill-formed;  gcd  is not visible
  }
</PRE>
</BLOCKQUOTE>

by

<BLOCKQUOTE>
<PRE>
  template&lt;typename T&gt; class number {
     public:
          number(int);
          //...
          friend number gcd(number x, number y) { return 0; }
     private:
          //...
  };

  void g()
  {
          number&lt;double&gt; a(3), b(4);
          //...
          a = gcd(a,b);           //  finds  gcd  because  number&lt;double&gt;  is an
                                  //  associated class, making  gcd  visible
                                  //  in its namespace (global scope)
          b = gcd(3,4);           //  ill-formed;  gcd  is not visible
  }
</PRE>
</BLOCKQUOTE>

<P><I>Drafting note: Added "return" to the friend function, removed
references in gcd arguments, added access specifiers.</I></P>

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