2039. Issues with std::reverse and std::copy_if

Section: 26.7.1 [alg.copy], 26.7.10 [alg.reverse] Status: C++14 Submitter: Nikolay Ivchenkov Opened: 2011-03-02 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

1. In the description of std::reverse

   Effects: For each non-negative integer i <= (last - first)/2, applies iter_swap to all pairs of iterators first + i, (last - i) - 1.

   should be changed to

   Effects: For each non-negative integer i < (last - first)/2, applies iter_swap to all pairs of iterators first + i, (last - i) - 1.

   Here i shall be strictly less than (last - first)/2.

2. In the description of std::copy_if Returns paragraph is missing.

[2011-03-02: Daniel drafts wording]

Proposed resolution:

1. Modify 26.7.10 [alg.reverse] p. 1 as indicated:

   1 Effects: For each non-negative integer i <= (last - first)/2, applies iter_swap to all pairs of iterators first + i, (last - i) - 1.

2. Add the following Returns element after 26.7.1 [alg.copy] p. 9:

   template<class InputIterator, class OutputIterator, class Predicate>
   OutputIterator copy_if(InputIterator first, InputIterator last,
      OutputIterator result, Predicate pred);
   

   8 Requires: The ranges [first,last) and [result,result + (last - first)) shall not overlap.

   9 Effects: Copies all of the elements referred to by the iterator i in the range [first,last) for which pred(*i) is true.

   ?? Returns: The end of the resulting range.

   10 Complexity: Exactly last - first applications of the corresponding predicate.

   11 Remarks: Stable.