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value_or() requires that U is convertible to T

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Due to Vladimir Batov.
This commit is contained in:
Andrzej Krzemienski
2014-06-14 22:49:37 +02:00
parent 8fc2901fad
commit 31c9119266
9 changed files with 66 additions and 17 deletions
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11
doc/html/boost_optional/tutorial/design_overview/the_interface.html
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@ -98,10 +98,11 @@
</p>
<p>
Such a <span class="emphasis"><em>de facto</em></span> idiom for referring to optional objects
can be formalized in the form of a concept: the <a href="../../../../../../utility/OptionalPointee.html" target="_top">OptionalPointee</a>
concept. This concept captures the syntactic usage of operators <code class="computeroutput"><span class="special">*</span></code>, <code class="computeroutput"><span class="special">-&gt;</span></code>
and contextual conversion to <code class="computeroutput"><span class="keyword">bool</span></code>
to convey the notion of optionality.
can be formalized in the form of a concept: the <a href="../../../../../../utility/OptionalPointee.html" target="_top"><code class="computeroutput"><span class="identifier">OptionalPointee</span></code></a> concept. This
concept captures the syntactic usage of operators <code class="computeroutput"><span class="special">*</span></code>,
<code class="computeroutput"><span class="special">-&gt;</span></code> and contextual conversion
to <code class="computeroutput"><span class="keyword">bool</span></code> to convey the notion
of optionality.
</p>
<p>
However, pointers are good to <span class="underline">refer</span>
@ -127,7 +128,7 @@
this semantics, so are inappropriate for the initialization and transport
of optional values, yet are quite convenient for handling the access to
the possible undefined value because of the idiomatic aid present in the
<a href="../../../../../../utility/OptionalPointee.html" target="_top">OptionalPointee</a>
<a href="../../../../../../utility/OptionalPointee.html" target="_top"><code class="computeroutput"><span class="identifier">OptionalPointee</span></code></a>
concept incarnated by pointers.
</p>
<h6>

6
doc/html/boost_optional/tutorial/in_place_factories.html
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@ -31,9 +31,9 @@
One of the typical problems with wrappers and containers is that their interfaces
usually provide an operation to initialize or assign the contained object
as a copy of some other object. This not only requires the underlying type
to be <a href="../../../../../utility/CopyConstructible.html" target="_top">Copy Constructible</a>,
but also requires the existence of a fully constructed object, often temporary,
just to follow the copy from:
to be <a href="../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a>, but also requires
the existence of a fully constructed object, often temporary, just to follow
the copy from:
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span>
<span class="special">{</span>