Re: [boost] iterator_adaptors question

From: David A. Greene (greened_at_[hidden])
Date: 2002-11-05 15:33:18

scleary_at_[hidden] wrote:
>>From: David A. Greene [mailto:greened_at_[hidden]]
>>
>><snip>
>>
>>Nowhere is "decrement" declared or defined in the filter_iterator
>>policies yet it can still be used with iterator_adaptor.  How
>>does this work?  Shouldn't the compiler complain that
>>iterator_adaptor::operator--() can't find
>>filter_iterator_policies::decrement?  I could understand if
>>operator-- were a template member but it's not.  I'm obviously
>>missing something.  What is it?
> 
> 
> Well, it's not really "used" by iterator_adaptor.  Since iterator_adaptor is
> a template class, the compiler will not instantiate its member functions
> unless they are actually used (i.e., called).  This is true even though
> operator-- is not a template member.

Oh!  Well, I learned something new today.  I was under the impression
that when a class template is instantiated all of its non-template
members are also instantiated.

Hmm...this makes a few things I've been working on a bit easier.

                     -Dave

-- 
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  and you know how big he was."  --  James P. Johnson