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[istream.sentry] Minor tweaks #8198

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[istream.sentry] Minor tweaks #8198

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b28d744
[istream.sentry] Minor tweaks
cpplearner Sep 1, 2025
61aaf2e
Address review comments
cpplearner Nov 19, 2025
a41ccee
Address review comments
cpplearner Nov 20, 2025
38963ad
Address review comments
cpplearner Nov 22, 2025
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19 changes: 5 additions & 14 deletions source/iostreams.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -4571,7 +4571,7 @@
that are part of the library.
The semantics of the constructor used in user code is as specified.
\end{footnote}
If \tcode{noskipws} is zero and
If \tcode{noskipws} is \tcode{false} and
\tcode{is.flags() \& ios_base::skipws}
is nonzero, the function extracts and discards each character as long as
the next available input character \tcode{c} is a whitespace character.
Expand All @@ -4585,13 +4585,11 @@
\tcode{setstate(failbit | eofbit)}
(which may throw
\tcode{ios_base::failure}).
After any preparation is completed, \exposid{ok_} is set to the value of \tcode{is.good()}.
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@jwakely jwakely Nov 19, 2025

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As this describes the final step, I think it would make more sense to be right at the end, after the "During preparation" sentence (maybe as a separate paragraph).

That way the structure would be:

  • The function extracts and discards each whitespace character.
  • If extracting a character returns eof, set failbit|eofbit.
  • Whitespace is determined using ctype.
  • The constructor may set failbit and throw. (for ... reasons? I guess the footnote covers that)
  • After any preparation is completed, set ok_.

What do you think?

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@cpplearner cpplearner Nov 19, 2025 •
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IMO this makes sense if we drop this \remarks macro.

draft/source/iostreams.tex

Line 4591 in 61aaf2e

\remarks

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@jwakely jwakely Nov 19, 2025

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Ah yes, agreed.


\pnum
\remarks
The constructor
\begin{codeblock}
explicit sentry(basic_istream& is, bool noskipws = false)
\end{codeblock}
This constructor
uses the currently imbued locale in \tcode{is},
to determine whether the next input character is
whitespace or not.
Expand All @@ -4600,19 +4598,12 @@
To decide if the character \tcode{c} is a whitespace character,
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@timsong-cpp timsong-cpp Nov 13, 2025

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While we are here, we can also drop the quote of the constructor signature in the previous paragraph.

Like...it's a Remarks for this constructor. Do we really need to say yet again that we are talking about this constructor?

the constructor performs as if it executes the following code fragment:
\begin{codeblock}
const ctype<charT>& ctype = use_facet<ctype<charT>>(is.getloc());
if (ctype.is(ctype.space, c) != 0)
const ctype<charT>& ct = use_facet<ctype<charT>>(is.getloc());
if (ct.is(ct.space, c))
// \tcode{c} is a whitespace character.
\end{codeblock}

\pnum
If, after any preparation is completed,
\tcode{is.good()}
is
\tcode{true},
\tcode{\exposid{ok_} != false}
otherwise,
\tcode{\exposid{ok_} == false}.
During preparation, the constructor may call
\tcode{setstate(failbit)}
(which may throw
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