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Section: 27 [algorithms], 28 [numerics] Status: New Submitter: Gašper Ažman Opened: 2017-05-10 Last modified: 2017-07-12
Priority: 3
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Discussion:
While researching whether the proposed resolution of Iterators of Containers of move-only types do not model InputIterator
(LWG 2962(i)), I came across several algorithms that underspecify their requirements, mostly with regard to some associated type of the iterator type they operate on. A list can be found below.
<algorithm>
and <numeric>
follows.
With the advent of concepts, these algorithms will need better specifications if we are ever hoping to be allowed to overload based on them. I want this issue to bring the standard algorithms closer to having their concept requirements directly transcribable to library annotations.
Suggested resolution:
copy
, copy_if
, copy_n
, copy_backward
Add to description: *result
shall be assignable from *first
.
move
, move_backward
Add to description: *result
shall be move-assignable from *first
.
transform
Add to description: The result of the expression op(*first)
or binary_op(*first1, *first2)
shall be writable to result
.
rotate_copy
Add to description: *first
shall be writable to result
.
merge
Add to description: *first1
and *first2
shall be writable to result
..
set_union
, set_intersection
, set_difference
, set_symmetric_difference
Add to description: *first1
and *first2
shall be writable to result
.
partial_sum
acc
is not defined.
acc
, a variable of InputIterator
's value type, shall be constructible
adjacent_difference
acc
is not defined.
acc
, a variable of InputIterator
's value type, shall be MoveAssignable
and shall be
constructible
from the type of *first
.
iota
iota
is mis-specified. Since the expression we need to support is *first = value
: *first
is required to be of type InputIterator::reference
, and value is an lvalue of type T
. The current
specification allows calling iota
with a const
output iterator!
T
shall be convertible to ForwardIterator
's value typevalue
shall be writable to
first
. The expression *first = value
shall not modify value
.
[2017-07 Toronto Monday issue prioritization]
Priority 3; Marshall to work with Gaspar to improve wording.
Proposed resolution: