Re: An alternative to possreps
From: Bob Badour <bob_at_badour.net>
Date: Thu, 09 Jun 2011 01:01:02 -0700
Message-ID: <PtqdnZrxzeQk4G3QnZ2dnUVZ5umdnZ2d_at_giganews.com>
>>David BL wrote:
>>
>>>On Jun 7, 9:49 pm, Bob Badour <b..._at_badour.net> wrote:
>>
>>>>David BL wrote:
>>
>>>>>On Jun 6, 9:26 pm, Erwin <e.sm..._at_myonline.be> wrote:
>>
>>>>>>On 31 mei, 11:54, David BL <davi..._at_iinet.net.au> wrote:
>>
>>>>>>>Is there anything in TTM that prohibits one from making every type a
>>>>>>>dummy type? Would that make it essentially the same approach which
>>>>>>>I've described?
>>
>>>>>>Not "in TTM". What prohibits this is "reality", I'd rather say.
>>
>>>>>>If you're interested in a subset of T, then you can't define this
>>>>>>subset by means of UNIONs involving T.
>>
>>>>>Yes, but that is not a problem. Let Ellipse be a "dummy type". If
>>>>>you're interested in a subtype Circle of Ellipse then you can simply
>>>>>declare Circle as another dummy type. I'm assuming you can declare
>>>>>subtype relationships between dummy types. In my approach you use
>>>>>these declarations:
>>
>>>>> type Ellipse;
>>>>> type Circle;
>>>>> Circle isa Ellipse;
>>
>>>>>I consider types like Circle and Ellipse to be defined by their
>>>>>operators. In that sense there is no problem treating all types as
>>>>>"dummy types".
>>
>>>>Either the operators define the equivalent of possreps or the type model
>>>> doesn't really describe ellipses and circles. So what are you trying
>>>>to achieve?
>>
>>>I'm suggesting the operators define the equivalent of possreps.
>>>Possreps are redundant.
>>
>>How do operators express that center is held invariant when changing
>>only radius? And vice versa?
>>
>>Or perhaps more clearly with complex number types: How do operators
>>express that phase is held constant when changing only magnitude? And
>>vice verse. Even though both realPart and imaginaryPart change?
Date: Thu, 09 Jun 2011 01:01:02 -0700
Message-ID: <PtqdnZrxzeQk4G3QnZ2dnUVZ5umdnZ2d_at_giganews.com>
David BL wrote:
> On Jun 8, 3:17 pm, Bob Badour <b..._at_badour.net> wrote: >
>>David BL wrote:
>>
>>>On Jun 7, 9:49 pm, Bob Badour <b..._at_badour.net> wrote:
>>
>>>>David BL wrote:
>>
>>>>>On Jun 6, 9:26 pm, Erwin <e.sm..._at_myonline.be> wrote:
>>
>>>>>>On 31 mei, 11:54, David BL <davi..._at_iinet.net.au> wrote:
>>
>>>>>>>Is there anything in TTM that prohibits one from making every type a
>>>>>>>dummy type? Would that make it essentially the same approach which
>>>>>>>I've described?
>>
>>>>>>Not "in TTM". What prohibits this is "reality", I'd rather say.
>>
>>>>>>If you're interested in a subset of T, then you can't define this
>>>>>>subset by means of UNIONs involving T.
>>
>>>>>Yes, but that is not a problem. Let Ellipse be a "dummy type". If
>>>>>you're interested in a subtype Circle of Ellipse then you can simply
>>>>>declare Circle as another dummy type. I'm assuming you can declare
>>>>>subtype relationships between dummy types. In my approach you use
>>>>>these declarations:
>>
>>>>> type Ellipse;
>>>>> type Circle;
>>>>> Circle isa Ellipse;
>>
>>>>>I consider types like Circle and Ellipse to be defined by their
>>>>>operators. In that sense there is no problem treating all types as
>>>>>"dummy types".
>>
>>>>Either the operators define the equivalent of possreps or the type model
>>>> doesn't really describe ellipses and circles. So what are you trying
>>>>to achieve?
>>
>>>I'm suggesting the operators define the equivalent of possreps.
>>>Possreps are redundant.
>>
>>How do operators express that center is held invariant when changing
>>only radius? And vice versa?
>>
>>Or perhaps more clearly with complex number types: How do operators
>>express that phase is held constant when changing only magnitude? And
>>vice verse. Even though both realPart and imaginaryPart change?
> > I agree that update operators are an important consideration. > > Nevertheless I don't think type systems per se should have anything to > do with specifying what update operators are available on variables.
Possreps don't. Received on Thu Jun 09 2011 - 10:01:02 CEST