NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part2/15859

Internet Message Format | 1996-08-05 | 2.2 KB

Path: morgan.cnu.edu!dlabell
From: [e-mail] (Daniel LaBell)
Newsgroups: comp.lang.c++
Subject: Re: C++ meta-problem
Date: 08 Apr 1996 15:56:24 GMT
Organization: A poorly-installed InterNetNews site
Message-ID: <[e-mail]>
References: <4jmtlg$[e-mail]>
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In-reply-to: [e-mail]'s message of 31 Mar 1996 14:32:32 -0700

In article <4jmtlg$[e-mail]> [e-mail] (Koen De Bosschere) writes:

) From: [e-mail] (Koen De Bosschere)
) Newsgroups: comp.lang.c++
) Date: 31 Mar 1996 14:32:32 -0700
)
) In order to prevent to write an iterator for every operation
) I want to perform on a list, I tried to write a kind of
) meta-iterator that would apply a particular method to
) all listnodes. For some reason, I cannot execute a
) function variable on an object. Does anyone has an
) idea how I can solve this problem?
)
[...]
) void iterate(testclass *root, void (testclass::*f)())
) {
)   testclass *p = root;
)   while (p) {
)     p->f();      //  <--- here the compiler generates an error (see below)
)     p = p->getnext();
)   }
) }
[...]

I have just done something somewhat like this myself, but I can't fully
see what exactly what you're trying to do with 'p->f();'  but I think the
concept is similiar.

(here's the part of the code that I think is relevant)

void binSrchTree::inorder( void ( *proccessFunc) (class record a))
{
  if ( root == NULL )
    return ;
  inorder ( root, proccessFunc );
}

void binSrchTree::inorder( binSrchTreeNode* n,
                          void (*proccessFunc) (class record a))
{

  if ( n->leftChild != NULL )
    inorder( n->leftChild, proccessFunc );
  (*proccessFunc) (n->data);
  if ( n->rightChild != NULL )
    inorder( n->rightChild, proccessFunc );
}

void PrintRecAndCompute ( record a )
{
  Count++;
  AddToAverages( a );
  cout.flags( ios::left );
  cout << setw(25) << a.name << setprecision(4) << a.grades[0]
    << TAB  << setprecision(4) << a.grades[1]
      << TAB << setprecision(4) << a.grades[2]
     << TAB << setprecision(4)  << a.grades[3] << endl;
}

I'd call it with a line like this:
    Tree1.inorder(PrintRecAndCompute);
--
Daniel LaBell