entry (was Re: Pointers to functions)

[David Collier-Brown]

In article <1988Mar11.221528.1392 at utzoo.uucp> henry at utzoo.uucp (Henry Spencer) writes:
>               It's also not at all clear that it
>is particularly useful, which is probably why nobody ever did anything
>with the "entry" keyword.

  It was useful in PL/1 for simulating C-like static-to-file
variables and C++-like packages... (sudden thought: ++- should be a
new operator in D).
  It got dropped just about the time it might have proved usefull,
much to my relief. C++ is much cleaner than:

balanced_binary_tree: procedure returns ptr; begin;
	declare 1 tree;
		(2 left, 2 right, 2 ptr) ptr
		based on (p);

	on misallocate goto cleanup;
	allocate (tree) set(p);
	return p;
  cleanup:
	return null;

newleft: entry(p,q) returns ptr; begin;
	declare p, q ptr;
	if (p->left = null) then do;
		p->left = balanced_binary_tree;
		p->left->ptr = q;
	end do;
	else do;
		rebalance(p,q);
	end do;
	return p->left;
end;
...

  The Multicians managed to avoid this almost entirely, the unicians
left it out of the language and the tune-in-next-weekians found a
better way.

  Never let it be said that we aren't making progress.
-- 
 David Collier-Brown.                 {mnetor yunexus utgpu}!geac!daveb
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