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Use mp_product_q in example

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Peter Dimov
2017-05-13 21:11:23 +03:00
parent 647f669353
commit ac28cf9b3f
2 changed files with 8 additions and 4 deletions
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7
doc/html/mp11.html
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@@ -436,7 +436,7 @@
just a matter of applying it over the possible combinations of the variant
values:
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">R</span> <span class="special">=</span> <span class="identifier">mp_product</span><span class="special">&lt;</span><span class="identifier">Qret</span><span class="special">&lt;</span><span class="identifier">F</span><span class="special">&gt;::</span><span class="keyword">template</span> <span class="identifier">fn</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">remove_reference_t</span><span class="special">&lt;</span><span class="identifier">V</span><span class="special">&gt;...&gt;;</span>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">R</span> <span class="special">=</span> <span class="identifier">mp_product_q</span><span class="special">&lt;</span><span class="identifier">Qret</span><span class="special">&lt;</span><span class="identifier">F</span><span class="special">&gt;,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">remove_reference_t</span><span class="special">&lt;</span><span class="identifier">V</span><span class="special">&gt;...&gt;;</span>
</pre>
<p>
Why does this work? <code class="computeroutput"><span class="identifier">mp_product</span><span class="special">&lt;</span><span class="identifier">F</span><span class="special">,</span>
@@ -444,6 +444,9 @@
where <code class="computeroutput"><span class="identifier">Ui</span></code> traverse all possible
combinations of list values. Since in our case all <code class="computeroutput"><span class="identifier">Li</span></code>
are <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">variant</span></code>, the result will also be <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">variant</span></code>.
(<code class="computeroutput"><span class="identifier">mp_product_q</span></code> is the same
as <code class="computeroutput"><span class="identifier">mp_product</span></code>, but for quoted
metafunctions such as our <code class="computeroutput"><span class="identifier">Qret</span><span class="special">&lt;</span><span class="identifier">F</span><span class="special">&gt;</span></code>.)
</p>
<p>
One more step remains. Suppose that, as above, we're passing two variants
@@ -1897,7 +1900,7 @@
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"><p><small>Last revised: May 13, 2017 at 18:01:55 GMT</small></p></td>
<td align="left"><p><small>Last revised: May 13, 2017 at 18:11:09 GMT</small></p></td>
<td align="right"><div class="copyright-footer"></div></td>
</tr></table>
<hr>

5
doc/mp11/examples.qbk
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@@ -115,10 +115,11 @@ We'll first define a helper quoted metafunction `Qret<F>` that returns the resul
With `Qret` in hand, a `variant` of the possible return types is just a matter of applying it over the possible combinations of the variant values:
using R = mp_product<Qret<F>::template fn, std::remove_reference_t<V>...>;
using R = mp_product_q<Qret<F>, std::remove_reference_t<V>...>;
Why does this work? `mp_product<F, L1<T1...>, L2<T2...>, ..., Ln<Tn...>>` returns `L1<F<U1, U2, ..., Un>, ...>`, where `Ui` traverse all
possible combinations of list values. Since in our case all `Li` are `std::variant`, the result will also be `std::variant`.
possible combinations of list values. Since in our case all `Li` are `std::variant`, the result will also be `std::variant`. (`mp_product_q` is
the same as `mp_product`, but for quoted metafunctions such as our `Qret<F>`.)
One more step remains. Suppose that, as above, we're passing two variants of type `std::variant<short, int, float>` and `F` is
`[]( auto const& x, auto const& y ){ return x + y; }`. This will generate `R` of length 9, one per each combination, but many of those