In article <3lf4gd$k2s@panix.com>, Atman Binstock <ajb@panix.com> wrote:
>
>Hi,
> Could someone tell me what the current draft standard says
>about uncalled class template members? Need they be checked before
>allowing instantiation of the class?  For example, if Vector<T>::sort()
>uses operator<(const T&, const T&), can you make a Vector<X>, where X
>does not support operator<, if Vector<X>::sort() is never called?

 Yes, you are supposed to be able to provided
Vector<X>::sort() is not _used_. That includes calling it,
but if it is virtual it is also considered "used".

 Note quite a few compilers do not yet provide this
functionality.


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        JOHN (MAX) SKALLER,         INTERNET:maxtal@suphys.physics.su.oz.au
 Maxtal Pty Ltd,
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In article 27135@mulga.cs.mu.OZ.AU, fjh@munta.cs.mu.OZ.AU (Fergus Henderson) writes:
>ajb@panix.com (Atman Binstock) writes:
>
>> Could someone tell me what the current draft standard says
>>about uncalled class template members?
>
>No.  In fact the implementation _must not_ check them (other than
>syntax checking).
>

The draft standard seems to have it both ways for uncalled virtual methods:

  An implementation shall not instantiate a function or a class that
  does not require instantiation.  However,  virtual  functions can be
  instantiated for implementation purposes.

I'd read that as saying a compliant implementation can reject a class
with a problematical yet uncalled member function if that function is
virtual.


---
~THol()

Thomas Holaday
holaday_thomas@jpmorgan.com
tlhol@ibm.net
70407.534@compuserve.com

John Max Skaller (maxtal@Physics.usyd.edu.au) wrote:
: In article <3lf4gd$k2s@panix.com>, Atman Binstock <ajb@panix.com> wrote:
: > Could someone tell me what the current draft standard says
: >about uncalled class template members? Need they be checked before
: >allowing instantiation of the class?  For example, if Vector<T>::sort()
: >uses operator<(const T&, const T&), can you make a Vector<X>, where X
: >does not support operator<, if Vector<X>::sort() is never called?

:  Yes, you are supposed to be able to provided
: Vector<X>::sort() is not _used_. That includes calling it,
: but if it is virtual it is also considered "used".

What if you explicitly instantiate it?
 // fuzzy on syntax here..
 template Vector<X>;
--
        Tony Cook - tony@online.tmx.com.au
                    100237.3425@compuserve.com

ajb@panix.com (Atman Binstock) writes:

> Could someone tell me what the current draft standard says
>about uncalled class template members? Need they be checked before
>allowing instantiation of the class?

No.  In fact the implementation _must not_ check them (other than
syntax checking).

>For example, if Vector<T>::sort()
>uses operator<(const T&, const T&), can you make a Vector<X>, where X
>does not support operator<, if Vector<X>::sort() is never called?

Yes, you can.

--
Fergus Henderson - fjh@munta.cs.mu.oz.au

Hi,
 Could someone tell me what the current draft standard says
about uncalled class template members? Need they be checked before
allowing instantiation of the class?  For example, if Vector<T>::sort()
uses operator<(const T&, const T&), can you make a Vector<X>, where X
does not support operator<, if Vector<X>::sort() is never called?

Thanks,
Atman Binstock