Re: [boost] Re: Boost algorithm library

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2001-07-26 11:33:19

On Thu, 26 Jul 2001, Ed Brey wrote:
> From: "Jeremy Siek" <jsiek_at_[hidden]>
> >
> > template <class Range>
> > void sort_heap(Range& range)
> > {
> >   std::sort_heap(range.begin(), range.end());
> > }
> >
>
> When will the reference ever need to be non-const?  All the underlying
> algorithms take iterators by value, and hence leave them untouched.

The above sort_heap() function is an example when the reference needs to
be non-const.

Suppose we are using the above sort_heap with std::vector.

std::vector<int> x(n);
...
sort_heap(x);

The elements in the vector will be modified by the algorithm, so we need
mutable iterators. Therefore, the calls to range.begin() and range.end()
better return iterator and not const_iterator. Therefore, we have to pass
by non-const reference in order to get the mutable iterator.

Cheers,
Jeremy

----------------------------------------------------------------------
 Jeremy Siek                        www: http://www.lsc.nd.edu/~jsiek/
 Ph.D. Candidate, IU B'ton          email: jsiek_at_[hidden]
 Summer Manager, AT&T Research      phone: [phone]
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