Newsgroups: comp.lang.c++
Path: utzoo!utgpu!craig
From: craig@gpu.utcs.utoronto.ca (Craig Hubley)
Subject: Re: asking an object for its type
Message-ID: <1991Feb22.194649.13381@gpu.utcs.utoronto.ca>
Organization: Craig Hubley & Associates
References: <23984@netcom.COM> <1190@sheol.UUCP> <1991Feb19.000449.22255@gpu.utcs.utoronto.ca> <27C2D580.3B49@tct.uucp>
Date: Fri, 22 Feb 1991 19:46:49 GMT

In article <27C2D580.3B49@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
>According to craig@gpu.utcs.utoronto.ca (Craig Hubley):
>>But in more intelligent O-O languages, asking the type, or better,
>>asking if there is a diameter, is a fundamental operation in type
>>Object that all objects can do.
>
>"More intelligent"?  Your prejudices are showing.  :-)

Other languages support a syntax with fewer seams, and resolve efficiency
issues with an optimizer.  C++ deliberately doesn't do this and leaves
it in the hands of the programmer, therefore C++ as a language decides that
it will be less intelligent and force programmers to be more intelligent.

Although this may be a compliment to C++ programmers, it is also more work
for them, and it may be unnecessary in some places.

I didn't really think of this as a prejudice, just a statement of fact.

>C++ is statically typed.  And there is no requirement that all classes
>be derived from a hypthetical Object class.  So the features you desire
>cannot be accomplished in C++.

Nonsense.  There is absolutely no reason that the compiler cannot determine
that *circle* has a diameter at compile-time, indeed it MUST know that.  A
macro/function/who-cares like x.has_member(diameter) can be completely
optimized away at runtime where the type is unambiguous.  Where it is
ambiguous, the cost is exactly the same as a virtual function which was
your alternate solution, but one which would require me to change the
base class shape, which is unacceptable.

>BTW, I happen to find C++ an excellent tool for _exactly_ those
>reasons.  I pay only for those OOP features I need, and no more.

Nobody is suggesting a compromise to this principle.

>Chip Salzenberg at Teltronics/TCT      <chip@tct.uucp>, <uunet!pdn!tct!chip>


-- 
  Craig Hubley   "...get rid of a man as soon as he thinks himself an expert."
  Craig Hubley & Associates------------------------------------Henry Ford Sr.
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