Unwrapping output iterators in range algorithms by CaseyCarter · Pull Request #5015 · microsoft/STL (original) (raw)

This completes the last bits of the iterator unwrapping design for Ranges algorithms.

Detailed commit-wise description:

• Expand _Idl_distance design for Ranges
  • Add _Distance_unbounded to represent the distance between an iterator and unreachable_sentinel.
  • _Idl_distance takes iterator/sentinel pairs in C++20 mode.
  • Add _RANGES _Idl_distance(range), equivalent to _STD _Idl_distance but for sized_range instead of sized_sentinel_for.
  • Support integer-class counts in _Get_unwrapped_n.
• Simplify ranges::destroy_n. Now that _Get_unwrapped_n supports integer-class counts, we don't need to apply _Algorithm_int_t to _Count.
• Update operations on _Idl_distances
  • Refactor _Idl_dist_add:
    * Use if constexpr dispatch instead of overloading.
    * _Distance_unbounded plus anything is _Distance_unbounded.
  • Implement _Idl_dist_min to compute the smaller of two _Idl_distances.
• Rename Range algorithm output iterator parameters from _Result to _Output. This changes our convention. I think _Output is more appropriate than _Result for this purpose given that most algorithms produce more results than just the output sequence. This also makes _Result unambiguously available to refer to the return value of the algorithm which is consistent with our use of _UResult for intermediate unwrapped results.
• Unwrap outputs in ranges::copy
• Unwrap outputs in ranges::copy_backward
• Unwrap outputs in ranges::copy_if
• Unwrap outputs in ranges::copy_n
• Unwrap outputs in ranges::merge
• Unwrap outputs in ranges::move
• Unwrap outputs in ranges::move_backward
• Unwrap outputs in ranges::replace_copy
• Unwrap outputs in ranges::replace_copy_if
• Unwrap outputs in ranges::reverse_copy
• Unwrap outputs in ranges::rotate_copy
• Unwrap outputs in ranges::sample
• Unwrap outputs in ranges::transform (The warning suppression is necessary to prevent the static analyzer diagnosing the computation of _Min_size_determinable as redundant when _Rng1 and _Rng2 are the same type.)

Fixes #893.