Path: utzoo!mnetor!uunet!husc6!mit-eddie!bbn!rochester!PT.CS.CMU.EDU!IUS1.CS.CMU.EDU!edw
From: edw@IUS1.CS.CMU.EDU (Eddie Wyatt)
Newsgroups: comp.lang.misc
Subject: Re: From Modula to Oberon
Message-ID: <1139@PT.CS.CMU.EDU>
Date: 16 Mar 88 17:40:23 GMT
References: <2827@enea.se> <1557@pasteur.Berkeley.Edu> <3764@bloom-beacon.MIT.EDU> <22162@bbn.COM>
Sender: netnews@PT.CS.CMU.EDU
Organization: Carnegie-Mellon University, CS/RI
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> 
>   The debate about CLU iterators misses an important point: CLU iterators are
> coroutines, which C does not have.  The implication is that per-iteration state
> is nicely hidden in CLU ("on the stack" in the coroutine local variables), and
> has to be explicitly managed in C (or any other coroutine-free language) by
> putting the state into globals or making the user hang on to the state.
> 

   But do you need coroutines to implimented generlized iteration.  
I think not.  The optional solution I posted should allow you
to perform the same task.  

  The optional solution was to  provided the iteration function a function
to invoke on each member of the enumerated list.  A single call would be
made to iterate through the list.

Example:

	void iterate_inorder(root,func)
	    TREE *root;
	    void (*func)();
	    {
	    if (root != NULLPTR(TREE))
		{
	    	iterate_inorder(root->left,func);
	    	func(root->val);
	    	iterate_inorder(root->right,func);
		}
	    }

    I do see one problem though, which is dealing with variable
    referenced  inside the loop.  They would have to become
    global.  Comments as to why this method might not work in general?
-- 

Eddie Wyatt 				e-mail: edw@ius1.cs.cmu.edu