Issue 1029: Specialized algorithms for memory management need to be concept-constrained templates (original) (raw)

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1029. Specialized algorithms for memory management need to be concept-constrained templates

Section: 26.11 [specialized.algorithms] Status: NAD Concepts Submitter: Alisdair Meredith Opened: 2009-03-11 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Addresses UK 210 [CD1]

Related to 582(i)

Specialized algorithms for memory management need requirements to be easily usable in constrained templates.

[ Summit: ]

We look forward to a paper on this topic. We recommend no action until a paper is available.

[ Post Summit Alisdair provided wording. ]

[ Post Summit: ]

Daniel adds:

1. I suggest Size should require IntegralLike and not UnsignedIntegralLike, because otherwise simple int-literals could not be provided as arguments and it would conflict with other algorithms that only require IntegralLike.
2. The current for-loop-test relies on evaluation in boolean context which is not provided by ArithmeticLike and it's refinements. I propose to change the corresponding for-loop-headers to:
3. for uninitialized_copy_n: for ( ; n > Size(0); ++result, ++first, --n) {
4. for uninitialized_fill_n: for (; n > Size(0); ++first, --n) {

Alisdair adds:

For the record I agree with Daniel's suggestion.

Proposed resolution:

20.2 [memory] p2

Update the synopsis for <memory>

template <class InputIterator InIter, class ForwardIterator OutputIterator<auto, InIter::reference> OutIter> requires ForwardIterator ForwardIterator OutIter uninitialized_copy(InputIterator InIter first, InputIterator InIter last, ForwardIterator OutIter result);

template <class InputIterator InIter, class IntegralLike Size, class ForwardIterator OutputIterator<auto, InIter::reference> OutIter> requires ForwardIterator ForwardIterator OutIter uninitialized_copy_n(InputIterator InIter first, Size n, ForwardIterator OutIter result);

template <class ForwardIterator Iter, class ObjectType T> requires Constructible< Iter::value_type, const T& > void uninitialized_fill(ForwardIterator Iter first, ForwardIterator Iter last, const T& x);

template <class ForwardIterator Iter, class IntegralLike Size, class ObjectType T> requires Constructible< Iter::value_type, const T& > void uninitialized_fill_n(ForwardIterator Iter first, Size n, const T& x);

Update as follows:

uninitialized_copy 26.11.5 [uninitialized.copy]

template <class InputIterator InIter, class ForwardIterator OutputIterator<auto, InIter::reference> OutIter> requires ForwardIterator ForwardIterator OutIter uninitialized_copy(InputIterator InIter first, InputIterator InIter last, ForwardIterator OutIter result);

-1- Effects:

for (; first != last; ++result, ++first) { new (static_cast<void*>(&*result)) typename iterator_traits OutIter::value_type(*first); }

-2- Returns: result

template <class InputIterator InIter, class IntegralLike Size, class ForwardIterator OutputIterator<auto, InIter::reference> OutIter> requires ForwardIterator ForwardIterator OutIter uninitialized_copy_n(InputIterator InIter first, Size n, ForwardIterator OutIter result);

-3- Effects:

for ( ; n > Size(0); ++result, ++first, --n) { new (static_cast<void*>(&*result)) typename iterator_traits OutIter::value_type(*first); }

-4- Returns: result

uninitialized_fill 26.11.7 [uninitialized.fill]

template <class ForwardIterator Iter, class ObjectType T> requires Constructible< Iter::value_type, const T& > void uninitialized_fill(ForwardIterator Iter first, ForwardIterator Iter last, const T& x);

-1- Effects:

for (; first != last; ++first) { new ( static_cast<void*>( &*first) ) typename iterator_traits Iter::value_type(x); }

uninitialized_fill_n [uninitialized.fill.n]

template <class ForwardIterator Iter, class IntegralLike Size, class ObjectType T> requires Constructible< Iter::value_type, const T& > void uninitialized_fill_n(ForwardIterator Iter first, Size n, const T& x);

-1- Effects:

for (; n-- > Size(0); ++first, --n) { new ( static_cast<void*>( &*first) ) typename iterator_traits Iter::value_type(x); }