uncalled class template members??

[Atman Binstock]

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

[Fergus Henderson]

a...@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 - f...@munta.cs.mu.oz.au

[John Max Skaller]

In article <3lf4gd$k...@panix.com>, Atman Binstock <a...@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.

--
JOHN (MAX) SKALLER, INTERNET:max...@suphys.physics.su.oz.au
Maxtal Pty Ltd,
81A Glebe Point Rd, GLEBE Mem: SA IT/9/22,SC22/WG21
NSW 2037, AUSTRALIA Phone: 61-2-566-2189

[Thomas Holaday,COMM]

In article 27...@mulga.cs.mu.OZ.AU, f...@munta.cs.mu.OZ.AU (Fergus Henderson) writes:

>a...@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...@jpmorgan.com
tl...@ibm.net
7040...@compuserve.com

[Tony Cook]

John Max Skaller (max...@Physics.usyd.edu.au) wrote:
: In article <3lf4gd$k...@panix.com>, Atman Binstock <a...@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 - to...@online.tmx.com.au
10023...@compuserve.com