Potential patent issues

[spir]

On 01/21/2011 03:51 PM, Don wrote:
> Don wrote:
>> BlazingWhitester wrote:
>>> I spotted some patents that can theaten current DMD implementation.
>>> Wanted to clarify things.
>>>
>>> http://www.freepatentsonline.com/6185728.pdf - this patent describes
>>> method pointers implementation (delegates)
>>
>> This was obviously a patent aimed at protecting Delphi from VB. It's
>> all about the RAD designer: visual connections between GUI elements
>> and events has a 1:1 correspondence with code; delegates are used to
>> achieve this.
>>
>> D delegates can store a data pointer to a nested function, or to an
>> object. This is rather more general (not an object-oriented feature),
>> and doesn't provide a 1:1 correspondence to visuals.
>> I presume they were only able to satisfy the requirements for novelty
>> and non-obviousness, because of the RAD usage. In fact, there doesn't
>> seem to be any suggestion that delegates would be used for anything else.
>> The more general idea of storing a data pointer and a function pointer
>> together is simple and obvious, and surely has prior art.
>
> D's delegate scheme is essentially the same as described by Richard
> Hickey, "C++ report" (Feb 1995).
>
> See also a discussion on comp.std.c++, Feb 1996, titled "Generic Object
> Callbacks". Ian Willmott states:
> "I suggest that a new data type needs to be added to the language. We
> could call it "pointer-to-bound-member-function".
> ...
> Conceptually, it is a two-element structure consisting of
> pointer into data space, identifying an object, and a pointer into
> code space, identifying a member function on that object. The static
> type of such a variable is the signature (return type and arguments)
> of the member functions it is compatible with, just as the type of a
> regular function pointer is the signature of the functions it can
> reference. The only operations defined for this type are assignment,
> equality, and callthrough. Static typechecking is done at the point
> where a value of this type is created, and where a call is made
> through it. "
>
> Borland's patent dates from Feb 6, 2001. They were SIX YEARS too late.
> <g>

IIUC, the structure you describe is /exactly/ the same, both concretely 
and semantically as Oberon-2 "type-bound procedures" (read: virtual 
methods). Oberon-2 was created in 1991, IIRC. This makes 10 years ;-)
Unlike you, I don't consider D's delegate to follow the same scheme. 
Sure, it's a pair of pointers, one of which point to a routine (to use a 
neutral word). But in the case of D the second one does not point to to 
a type/object, but to the definition scope (environment). This is very 
different, isn't it?
Thus I would consider D to not even be concerned by the patent. If you 
use a 3-integer struct to store a color, do you have to pay royalties to 
the owner of a patent about a 3-integer struct used to store a position? 
Indeed, lawyers...

Denis
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