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Article #938

Help needed on function templates

#938
From: seedy
Date: Fri, 05 Apr 1996 02:17
57 lines
1857 bytes
When attempted to compile the following code I got the following error :
I use g++ (2.7.1) on HP-UX 10.x.

news.cc: In function `int equal(const class abc &, const class abc &)':
news.cc:23: no match for `operator ==(class abc, class abc)'

#include <iostream.h>

class abc {
    public : 
       abc( int x )
	  {
	  a = x;
	  b = 0;
	  }
       int a;
       int b;
       inline int operator ==(abc x)
           {
              return ((a==x.a) && (b==x.b));
           }
    };



template < class Element>
inline int equal (Element const& e1, Element const& e2) 
{
  return e1 == e2;

}

main()
{
abc a1(5), a2(5);

cout << "Return value is = " << equal(a1, a2) << endl;
}


Even though the 'operator ==' is overloaded in class abc, compiler is
reporting match not found. By making the overloaded function 'operator =='
as friend to 'class abc' I could resolve the problem, because in this case,
this overloaded function becomes outsider function.

As far as I know, template instantiation for function 'equal will be done
for 'class abc'(because the passed parameters are of type class abc), 
and so the corresponding member function 'operator ==' can be used for 
template variables e1 and e2.

Any explanations?  Please forward your response to 'seedy@trigent.com'
or post it here.

Regards,

Praveen.
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From: seedy@ultranet.com
Newsgroups: gnu.g++.help,comp.sys.lang.c++,comp.lang.c++
Subject: Help needed on function templates
Date: Thu, 04 Apr 96 19:17:06 PDT
Organization: UltraNet Communications, Inc.
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