P3923R0: Re NB US 164-203 (C++26 CD)

Fixes NB US 164-203 (C++26 CD).

Author: eisenwave

source/algorithms.tex

@@ -10425,8 +10425,7 @@
   and \tcode{proj1} and \tcode{proj2} be \tcode{identity\{\}}
   for the overloads with no parameters by those names;
 \item
-  $M$ be \tcode{last1 - first1} plus the number of elements in \range{first2}{last2}
-  that are not present in \range{first1}{last1};
+  $M$ be the number of elements in the sorted union (see below);
 \item
   \tcode{result_last} be \tcode{result + $M$}
   for the overloads with no parameter \tcode{result_last} or \tcode{result_r};
@@ -10442,8 +10441,21 @@
 
 \pnum
 \effects
-Constructs a sorted union of $N$ elements from the two ranges;
+Constructs a sorted union of the elements from the two ranges;
 that is, the set of elements that are present in one or both of the ranges.
+If \range{first1}{last1} contains $m$ elements
+that are equivalent to each other and
+\range{first2}{last2} contains $n$ elements that are equivalent to them,
+then all $m$ elements from the first range
+are included in the union, in order, and
+then the final $\max(n - m,0)$ elements from the second range
+are included in the union, in order.
+If, of those elements, $k$ elements from the first range
+are copied to the output range,
+then the first $\min(k,n)$ elements from the second range
+are considered \term{skipped}.
+Copies the first $N$ elements of the sorted union
+to the range \range{result}{result + $N$}.
 
 \pnum
 \returns
@@ -10456,10 +10468,9 @@
   for the overloads in namespace \tcode{ranges},
   if $N$ is equal to $M$.
 \item
-  Otherwise, \tcode{\{j1, j2, result_last\}}
+  Otherwise, \tcode{\{first1 + $A$, first2 + $B$, result_last\}}
   for the overloads in namespace \tcode{ranges},
-  where the iterators \tcode{j1} and \tcode{j2}
-  point to positions past the last copied or skipped elements
+  where $A$ and $B$ are the numbers of copied or skipped elements
   in \range{first1}{last1} and \range{first2}{last2}, respectively.
 \end{itemize}
 
@@ -10471,14 +10482,6 @@
 \pnum
 \remarks
 Stable\iref{algorithm.stable}.
-If \range{first1}{last1} contains $m$ elements
-that are equivalent to each other and
-\range{first2}{last2} contains $n$ elements
-that are equivalent to them,
-then all $m$ elements from the first range
-are copied to the output range, in order, and
-then the final $\max(n - m, 0)$ elements from the second range
-are copied to the output range, in order.
 \end{itemdescr}
 
 \rSec3[set.intersection]{\tcode{set_intersection}}
@@ -10555,8 +10558,7 @@
   and \tcode{proj1} and \tcode{proj2} be \tcode{identity\{\}}
   for the overloads with no parameters by those names;
 \item
-  $M$ be the number of elements in \range{first1}{last1}
-  that are present in \range{first2}{last2};
+  $M$ be the number of elements in the sorted intersection (see below);
 \item
   \tcode{result_last} be \tcode{result + $M$}
   for the overloads with no parameter \tcode{result_last} or \tcode{result_r};
@@ -10572,8 +10574,23 @@
 
 \pnum
 \effects
-Constructs a sorted intersection of $N$ elements from the two ranges;
+Constructs a sorted intersection of the elements from the two ranges;
 that is, the set of elements that are present in both of the ranges.
+If \range{first1}{last1} contains $m$ elements
+that are equivalent to each other and
+\range{first2}{last2} contains $n$ elements
+that are equivalent to them,
+the first $\min(m, n)$ elements
+are included in the sorted intersection.
+If, of those elements, $k$ elements from the first range
+are copied to the output range,
+then the first $k$ elements from the second range
+are considered \term{skipped}.
+If $N < M$, a non-copied element is also considered skipped
+if it compares less than the $(N+1)^\text{th}$ element
+of the sorted intersection.
+Copies the first $N$ elements of the sorted intersection
+to the range \range{result}{result + $N$}.
 
 \pnum
 \returns
@@ -10586,10 +10603,9 @@
   for the overloads in namespace \tcode{ranges},
   if $N$ is equal to $M$.
 \item
-  Otherwise, \tcode{\{j1, j2, result_last\}}
+  Otherwise, \tcode{\{first1 + $A$, first2 + $B$, result_last\}}
   for the overloads in namespace \tcode{ranges},
-  where the iterators \tcode{j1} and \tcode{j2}
-  point to positions past the last copied or skipped elements
+  where $A$ and $B$ are the numbers of copied or skipped elements
   in \range{first1}{last1} and \range{first2}{last2}, respectively.
 \end{itemize}
 
@@ -10601,12 +10617,6 @@
 \pnum
 \remarks
 Stable\iref{algorithm.stable}.
-If \range{first1}{last1} contains $m$ elements
-that are equivalent to each other and
-\range{first2}{last2} contains $n$ elements
-that are equivalent to them,
-the first $\min(m, n)$ elements
-are copied from the first range to the output range, in order.
 \end{itemdescr}
 
 \rSec3[set.difference]{\tcode{set_difference}}
@@ -10682,8 +10692,7 @@
   and \tcode{proj1} and \tcode{proj2} be \tcode{identity\{\}}
   for the overloads with no parameters by those names;
 \item
-  $M$ be the number of elements in \range{first1}{last1}
-  that are not present in \range{first2}{last2};
+  $M$ be the number of elements in the sorted difference (see below);
 \item
   \tcode{result_last} be \tcode{result + $M$}
   for the overloads with no parameter \tcode{result_last} or \tcode{result_r};
@@ -10699,10 +10708,17 @@
 
 \pnum
 \effects
-Copies $N$ elements of the range \range{first1}{last1}
-which are not present in the range \range{first2}{last2}
+Constructs a sorted difference between the elements from the two ranges;
+that is, the set of elements that are present
+in the range \range{first1}{last1} but not \range{first2}{last2}.
+If \range{first1}{last1} contains $m$ elements
+that are equivalent to each other and
+\range{first2}{last2} contains $n$ elements
+that are equivalent to them,
+the last $\max(m - n, 0)$ elements from \range{first1}{last1}
+are included in the sorted difference, in order.
+Copies the first $N$ elements of the sorted difference
 to the range \range{result}{result + $N$}.
-The elements in the constructed range are sorted.
 
 \pnum
 \returns
@@ -10718,8 +10734,8 @@
   Otherwise, \tcode{\{j1, result_last\}}
   for the overloads in namespace \tcode{ranges},
   where the iterator \tcode{j1}
-  points to the position past the last copied or skipped element
-  in \range{first1}{last1}.
+  points to the position of the element in \range{first1}{last1}
+  corresponding to the $(N+1)^\text{th}$ element of the sorted difference.
 \end{itemize}
 
 \pnum
@@ -10729,12 +10745,7 @@
 
 \pnum
 \remarks
-If \range{first1}{last1} contains $m$ elements
-that are equivalent to each other and
-\range{first2}{last2} contains $n$ elements
-that are equivalent to them,
-the last $\max(m - n, 0)$ elements from \range{first1}{last1}
-are copied to the output range, in order.
+Stable\iref{algorithm.stable}.
 \end{itemdescr}
 
 \rSec3[set.symmetric.difference]{\tcode{set_symmetric_difference}}
@@ -10813,14 +10824,12 @@
   and \tcode{proj1} and \tcode{proj2} be \tcode{identity\{\}}
   for the overloads with no parameters by those names;
 \item
-  $K$ be the number of elements in \range{first1}{last1} that are not present in \range{first2}{last2}.
-\item
-  $M$ be the number of elements in \range{first2}{last2} that are not present in \range{first1}{last1}.
+  $M$ be the number of elements in the sorted symmetric difference (see below);
 \item
-  \tcode{result_last} be \tcode{result + $M$ + $K$}
+  \tcode{result_last} be \tcode{result + $M$}
   for the overloads with no parameter \tcode{result_last} or \tcode{result_r};
 \item
-  $N$ be $\min(K + M, \ \tcode{result_last - result})$.
+  $N$ be $\min(M, \ \tcode{result_last - result})$.
 \end{itemize}
 
 \pnum
@@ -10831,12 +10840,24 @@
 
 \pnum
 \effects
-Copies the elements of the range \range{first1}{last1}
-that are not present in the range \range{first2}{last2},
-and the elements of the range \range{first2}{last2}
-that are not present in the range \range{first1}{last1}
+Constructs a sorted symmetric difference of the elements from the two ranges;
+that is, the set of elements that are present
+in exactly one of \range{first1}{last1} and \range{first2}\range{last2}.
+If \range{first1}{last1} contains $m$ elements
+that are equivalent to each other and
+\range{first2}{last2} contains $n$ elements
+that are equivalent to them,
+then $|m - n|$ of those elements are included in the symmetric difference:
+the last $m - n$ of these elements from \range{first1}{last1},
+in order, if $m > n$, and
+the last $n - m$ of these elements from \range{first2}{last2},
+in order, if $m < n$.
+If $N < M$, a non-copied element is considered \term{skipped}
+if it compares less than or equivalent to the $(N+1)^\text{th}$ element
+of the sorted symmetric difference,
+unless it is from the same range as that element and does not precede it.
+Copies the first $N$ elements of the sorted symmetric difference
 to the range \range{result}{result + $N$}.
-The elements in the constructed range are sorted.
 
 \pnum
 \returns
@@ -10849,10 +10870,9 @@
   for the overloads in namespace \tcode{ranges},
   if $N$ is equal to $M + K$.
 \item
-  Otherwise, \tcode{\{j1, j2, result_last\}}
+  Otherwise, \tcode{\{first1 + $A$, first2 + $B$, result_last\}}
   for the overloads in namespace \tcode{ranges},
-  where the iterators \tcode{j1} and \tcode{j2}
-  point to positions past the last copied or skipped elements
+  where $A$ and $B$ are the numbers of copied or skipped elements
   in \range{first1}{last1} and \range{first2}{last2}, respectively.
 \end{itemize}
 
@@ -10864,14 +10884,6 @@
 \pnum
 \remarks
 Stable\iref{algorithm.stable}.
-If \range{first1}{last1} contains $m$ elements
-that are equivalent to each other and
-\range{first2}{last2} contains $n$ elements
-that are equivalent to them,
-then $|m - n|$ of those elements shall be copied to the output range:
-the last $m - n$ of these elements from \range{first1}{last1} if $m > n$, and
-the last $n - m$ of these elements from \range{first2}{last2} if $m < n$.
-In either case, the elements are copied in order.
 \end{itemdescr}
 
 \rSec2[alg.heap.operations]{Heap operations}