Re: [boost] [function types] New tag type logic

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2005-06-30 07:39:35

Tobias Schwinger wrote:
> John Maddock wrote:
> 
>>>OK, here is my current top-candidate:
>>>
>>>  When classifying types it is often necessary to match against
>>>  several variations of one aspect.
>>>
>>>  There are special variations which make this possible. These are called
>>>  *abstract*.
>>>
>>>  The most important case is to match any variation; that is, to ignore
>>>  that aspect in the context of type classification. Because of this, 
>>>every
>>>aspect has at
>>>  least one abstract variation named "unspecified_" plus the aspect name.
>>
> 
> ;-( - I knew this would happen... I accidently hit the "Send"-button before the 
> post was finished...
> 
> 
>>That one also makes sense to me, I'm still not sure that "abstract" is the 
>>right word though :-)
>>
>>Explanation: to me if something is "abstract" then you need to add something 
>>to it, extend it in some way to make it concrete.  What you're doing is 
> 
> 
> Interesting... This is exactly why I came up with this term in the first place:
> 
> An abstract variation of an aspect does not concretely describe the aspect
> of the kind of type. It describes it, well, in an /abstract/ way:
> 
> Looking at classification, analog to pointer declaration, we constrain a (kind of) 
> type by specifying a special (kind of) type that only describes a category (but 
> nothing concrete).
> 
> Type synthesis is in some ways similar to a constructor call: actually we can't 
> create an "unspecified decorated" function type - we can only create an 
> undecorated or (member-)pointer-decorated or reference-decorated function type. So 
> there /is/ the kind of extension you describe, although implicitly done by a 
> default mechanism.

^^^^^^^^^^^^^^^^^^^^ and it is still helpful to give the user an idea how this 
works, in order to explain this mechanism.

> 
> "Abstract" let's the user intuitively suspect something like an "external tree 
> structure" (i.e. only leafes carry user data), that's why I like it.
> 

s/let's/lets/

> 
>>combining several concrete definitions to form a non-specific union of some 
>>kind.  So a quick trip to thesaurus.com suggests: "composite", "compound" or 
>>"mixed" as possible names, do any of these work for you?
>>
> 
> 
> I'm not convinced, yet. Maybe I'm having difficulties to fully understand you. Can 
> you perhaps try to clarify what makes "abstract" unsuitable in your opinion?
> 
> 
> Thanks,
> 
> Tobias
> 
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