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[iterator.concept.writable] Double if and one-item list #2568

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JohelEGP opened this issue Dec 7, 2018 · 2 comments
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[iterator.concept.writable] Double if and one-item list #2568

JohelEGP opened this issue Dec 7, 2018 · 2 comments

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@JohelEGP
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JohelEGP commented Dec 7, 2018 •
edited

draft/source/iterators.tex

Lines 1227 to 1236 in 38eb5e5

Let \tcode{E} be an an expression such that \tcode{decltype((E))} is \tcode{T},
and let \tcode{o} be a dereferenceable object of type \tcode{Out}.
\tcode{Out} and \tcode{T} model \tcode{Writable<Out, T>} only if
\begin{itemize}
\item If \tcode{Out} and \tcode{T} model
\tcode{Readable<Out> \&\& Same<iter_value_t<Out>, decay_t<T>{>}},
then \tcode{*o} after any above assignment is equal to
the value of \tcode{E} before the assignment.
\end{itemize}

This one-item list starts with an if, but its introducing paragraph ends with an if too.
@jensmaurer jensmaurer assigned jensmaurer and unassigned jensmaurer Dec 7, 2018
@jensmaurer
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And, reading through this, it seems intentional. The point here is that (beyond the syntactic requirements), a Writeable iterator that happens to also be a Readable iterator guarantees that you can read the just-written value back from the iterator. (Assuming the value types are the same.)
Just merging the duplicate "if"s would change the semantics.

@JohelEGP
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JohelEGP commented Dec 7, 2018

Right. After many rereads of your comment and the wording, I get it. Thank you.

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@JohelEGP @jensmaurer