overloaded function handles

[Judd Storrs]

On Wed, Jul 29, 2009 at 3:40 AM, Jaroslav Hajek <highegg at gmail.com> wrote:

>
> If you want to propose an alternative implementation, go ahead. I'm
> fairly sure that the idea of dropping the cache would result in
> inferior performance, but maybe you can manage something I just don't
> see.


Ack, no! I'm not suggesting we drop the cache! I'm just suggesting that one
way to avoid the patent would be to delay cache creation for type-based
overload until the handle is used the first time. For non-type-based
overload, the dispatch is fully resolvable at creation but IMHO that doesn't
infringe.

You're first reaction should be that if you delay cache creation until first
use it would result in an incorrect cache because it's created in the wrong
scope. What suggesting is that limitations of the Matlab language help out
here. For type-based dispatch I don't think there is any difference as long
as the file search path doesn't change between creation and use.

If the handle is anonymous or a subfunction or in the same file it can be
fully resolved at creation. In all other cases the cache is built at first
use only. The cache is used subsequently without performance penalty.

The reality of the Matlab language is that it does not permit you to create
type-overloaded subfunctions or type-overloaded anonymous functions. You
must use @class directories which requires the file path search mechanism. A
correct type-based overload cache can be built from any scope unless the
path is changed between handle creation and first use.

Essentially the patent only covers the case that a handle represents a cache
of type-overloaded functions containing multiple implementations and is also
created from the same scope that the handle is created.

By fully resolving some functions at creation and not creating the cache at
creation for all other cases the claims do not apply. And it's possible to
get very very close to what Matlab does. Deferring cache creation until
first use shouldn't cause a performance hit because the cache has to be
built once sometime anyway.


--judd
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