LWG3879 erase_if for flat_{,multi}set is incorrectly specified

Author: burblebee

source/containers.tex

@@ -17016,15 +17016,31 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\expects
+\tcode{Key} meets the \oldconcept{MoveAssignable} requirements.
+
 \pnum
 \effects
-Equivalent to:
-\begin{codeblock}
-auto [erase_first, erase_last] = ranges::remove_if(c, pred);
-auto n = erase_last - erase_first;
-c.erase(erase_first, erase_last);
-return n;
-\end{codeblock}
+Let $E$ be \tcode{bool(pred(as_const(e)))}.
+Erases all elements \tcode{e} in \tcode{c} for which $E$ holds.
+
+\pnum
+\returns
+The number of elements erased.
+
+\pnum
+\complexity
+Exactly \tcode{c.size()} applications of the predicate.
+
+\pnum
+\remarks
+Stable\iref{algorithm.stable}.
+If an invocation of \tcode{erase_if} exits via an exception,
+\tcode{c} is in a valid but unspecified state\iref{defns.valid}.
+\begin{note}
+\tcode{c} still meets its invariants, but can be empty.
+\end{note}
 \end{itemdescr}
 
 \rSec2[flat.multiset]{Class template \tcode{flat_multiset}}
@@ -17612,15 +17628,31 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\expects
+\tcode{Key} meets the \oldconcept{MoveAssignable} requirements.
+
 \pnum
 \effects
-Equivalent to:
-\begin{codeblock}
-auto [erase_first, erase_last] = ranges::remove_if(c, pred);
-auto n = erase_last - erase_first;
-c.erase(erase_first, erase_last);
-return n;
-\end{codeblock}
+Let $E$ be \tcode{bool(pred(as_const(e)))}.
+Erases all elements \tcode{e} in \tcode{c} for which $E$ holds.
+
+\pnum
+\returns
+The number of elements erased.
+
+\pnum
+\complexity
+Exactly \tcode{c.size()} applications of the predicate.
+
+\pnum
+\remarks
+Stable\iref{algorithm.stable}.
+If an invocation of \tcode{erase_if} exits via an exception,
+\tcode{c} is in a valid but unspecified state\iref{defns.valid}.
+\begin{note}
+\tcode{c} still meets its invariants, but can be empty.
+\end{note}
 \end{itemdescr}
 
 \rSec2[container.adaptors.format]{Container adaptors formatting}