boostorg/optional
1
0
Fork 1
mirror of https://github.com/boostorg/optional.git synced 2025-07-29 03:57:20 +02:00
Code Issues Packages Projects Releases Wiki Activity

docs -- expanded tutprial section

Browse Source
This commit is contained in:
Andrzej Krzemienski
2014-06-08 16:23:35 +02:00
parent d25b0cfd59
commit befd3970d7
14 changed files with 353 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
doc/html/boost_optional/quick_start/bypassing_unnecessary_default_construction.html
View File

@ -44,10 +44,10 @@
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">tie</span><span class="special">(</span><span class="identifier">begin</span><span class="special">,</span> <span class="identifier">end</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">getPeriod</span><span class="special">();</span>
</pre>
<p>
The second line works already, this is the capability of Boost.Tuple library,
but the first line won't work. We could set some invented initial dates,
but it is confusing and may be an unacceptable cost, given that these values
will be overwritten in the next line anyway. This is where <code class="computeroutput"><span class="identifier">optional</span></code> can help:
The second line works already, this is the capability of <a href="../../../../../tuple/index.html" target="_top">Boost.Tuple</a>
library, but the first line won't work. We could set some invented initial
dates, but it is confusing and may be an unacceptable cost, given that these
values will be overwritten in the next line anyway. This is where <code class="computeroutput"><span class="identifier">optional</span></code> can help:
</p>
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">Date</span><span class="special">&gt;</span> <span class="identifier">begin</span><span class="special">,</span> <span class="identifier">end</span><span class="special">;</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">tie</span><span class="special">(</span><span class="identifier">begin</span><span class="special">,</span> <span class="identifier">end</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">getPeriod</span><span class="special">();</span>

11
doc/html/boost_optional/quick_start/storage_in_containers.html
View File

@ -43,14 +43,9 @@
</pre>
<p>
This works because <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
is <code class="computeroutput"><span class="identifier">LessThanComparable</span></code> whenever
<code class="computeroutput"><span class="identifier">T</span></code> is <code class="computeroutput"><span class="identifier">LessThanComparable</span></code>.
In this case the state of being uninitialized is treated as a yet another
value of <code class="computeroutput"><span class="identifier">T</span></code>, which is compared
less than any value of <code class="computeroutput"><span class="identifier">T</span></code>.
So the set of values that type <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
can assume is {<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>, -2147483648, -2147483647, ..., -1,
0, 1, ..., 2147483647} (assuming a 32-bit <code class="computeroutput"><span class="keyword">int</span></code>).
is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> whenever <code class="computeroutput"><span class="identifier">T</span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. In this case
the state of being uninitialized is treated as a yet another value of <code class="computeroutput"><span class="identifier">T</span></code>, which is compared less than any value
of <code class="computeroutput"><span class="identifier">T</span></code>.
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>