forked from boostorg/mp11
Remove unnecessary C++14 use from examples
This commit is contained in:
Peter Dimov
+40
-17
@@ -304,8 +304,8 @@
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Let's suppose that we have written a metafunction <code class="computeroutput"><span class="identifier">result</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span>
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<span class="identifier">U</span><span class="special">></span></code>:
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">promote</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">promote</span><span class="special"><</span><span class="identifier">T</span><span class="special">>,</span> <span class="identifier">promote</span><span class="special"><</span><span class="identifier">U</span><span class="special">>>;</span>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">promote</span> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>::</span><span class="identifier">type</span><span class="special">;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">result</span> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span><span class="special"><</span><span class="identifier">promote</span><span class="special"><</span><span class="identifier">T</span><span class="special">>,</span> <span class="identifier">promote</span><span class="special"><</span><span class="identifier">U</span><span class="special">>>::</span><span class="identifier">type</span><span class="special">;</span>
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</pre>
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<p>
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that ought to represent the result of an arithmetic operation on the integer
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@@ -353,8 +353,8 @@
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<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">core</span><span class="special">::</span><span class="identifier">demangle</span><span class="special">(</span> <span class="keyword">typeid</span><span class="special">(</span><span class="identifier">T</span><span class="special">).</span><span class="identifier">name</span><span class="special">()</span> <span class="special">);</span>
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<span class="special">}</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">promote</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">promote</span><span class="special"><</span><span class="identifier">T</span><span class="special">>,</span> <span class="identifier">promote</span><span class="special"><</span><span class="identifier">U</span><span class="special">>>;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">promote</span> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>::</span><span class="identifier">type</span><span class="special">;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">result</span> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span><span class="special"><</span><span class="identifier">promote</span><span class="special"><</span><span class="identifier">T</span><span class="special">>,</span> <span class="identifier">promote</span><span class="special"><</span><span class="identifier">U</span><span class="special">>>::</span><span class="identifier">type</span><span class="special">;</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">test_result</span><span class="special">(</span> <span class="identifier">mp_list</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span>
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<span class="special">{</span>
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@@ -396,11 +396,33 @@
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<p>
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We then default-construct this tuple and pass it to <code class="computeroutput"><span class="identifier">tuple_for_each</span></code>.
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<code class="computeroutput"><span class="identifier">tuple_for_each</span><span class="special">(</span><span class="identifier">tp</span><span class="special">,</span> <span class="identifier">f</span><span class="special">)</span></code> calls <code class="computeroutput"><span class="identifier">f</span></code>
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for every tuple element; we use a (C++14) lambda that calls <code class="computeroutput"><span class="identifier">test_result</span></code>. (In pure C++11, we'd need
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to make <code class="computeroutput"><span class="identifier">test_result</span></code> a function
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object with a templated <code class="computeroutput"><span class="keyword">operator</span><span class="special">()</span></code> and pass that to <code class="computeroutput"><span class="identifier">tuple_for_each</span></code>
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directly.)
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for every tuple element; we use a (C++14) lambda that calls <code class="computeroutput"><span class="identifier">test_result</span></code>.
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</p>
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<p>
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In pure C++11, we can't use a lambda with an <code class="computeroutput"><span class="keyword">auto</span><span class="special">&&</span></code> parameter, so we'll have to make
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<code class="computeroutput"><span class="identifier">test_result</span></code> a function object
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with a templated <code class="computeroutput"><span class="keyword">operator</span><span class="special">()</span></code>
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and pass that to <code class="computeroutput"><span class="identifier">tuple_for_each</span></code>
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directly:
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</p>
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<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">test_result</span>
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<span class="special">{</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">></span> <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="identifier">mp_list</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="keyword">const</span>
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<span class="special">{</span>
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<span class="keyword">using</span> <span class="identifier">T3</span> <span class="special">=</span> <span class="keyword">decltype</span><span class="special">(</span> <span class="identifier">T1</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">T2</span><span class="special">()</span> <span class="special">);</span>
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<span class="keyword">using</span> <span class="identifier">T4</span> <span class="special">=</span> <span class="identifier">result</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>;</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">is_same</span><span class="special"><</span><span class="identifier">T3</span><span class="special">,</span> <span class="identifier">T4</span><span class="special">>::</span><span class="identifier">value</span><span class="special">?</span> <span class="string">"[PASS] "</span><span class="special">:</span> <span class="string">"[FAIL] "</span> <span class="special">)</span>
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<span class="special"><<</span> <span class="identifier">name</span><span class="special"><</span><span class="identifier">T1</span><span class="special">>()</span> <span class="special"><<</span> <span class="string">" + "</span> <span class="special"><<</span> <span class="identifier">name</span><span class="special"><</span><span class="identifier">T2</span><span class="special">>()</span> <span class="special"><<</span> <span class="string">" -> "</span> <span class="special"><<</span> <span class="identifier">name</span><span class="special"><</span><span class="identifier">T3</span><span class="special">>()</span> <span class="special"><<</span> <span class="string">", result: "</span> <span class="special"><<</span> <span class="identifier">name</span><span class="special"><</span><span class="identifier">T4</span><span class="special">>()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
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<span class="special">}</span>
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<span class="special">};</span>
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<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="keyword">using</span> <span class="identifier">L</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">tuple</span><span class="special"><</span><span class="keyword">char</span><span class="special">,</span> <span class="keyword">short</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">unsigned</span><span class="special">,</span> <span class="keyword">long</span><span class="special">,</span> <span class="keyword">unsigned</span> <span class="keyword">long</span><span class="special">>;</span>
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<span class="identifier">tuple_for_each</span><span class="special">(</span> <span class="identifier">mp_product</span><span class="special"><</span><span class="identifier">mp_list</span><span class="special">,</span> <span class="identifier">L</span><span class="special">,</span> <span class="identifier">L</span><span class="special">>(),</span> <span class="identifier">test_result</span><span class="special">()</span> <span class="special">);</span>
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<span class="special">}</span>
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</pre>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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@@ -419,7 +441,9 @@
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arguments. For that, we need a metafunction that applies <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span></code>
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to each pair of elements and gathers the results into a tuple:
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Tp1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Tp2</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">common_tuple</span> <span class="special">=</span> <span class="identifier">mp_transform</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special">,</span> <span class="identifier">Tp1</span><span class="special">,</span> <span class="identifier">Tp2</span><span class="special">>;</span>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">common_type_t</span> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type</span><span class="special"><</span><span class="identifier">T</span><span class="special">...>::</span><span class="identifier">type</span><span class="special">;</span> <span class="comment">// standard in C++14</span>
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<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Tp1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Tp2</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">common_tuple</span> <span class="special">=</span> <span class="identifier">mp_transform</span><span class="special"><</span><span class="identifier">common_type_t</span><span class="special">,</span> <span class="identifier">Tp1</span><span class="special">,</span> <span class="identifier">Tp2</span><span class="special">>;</span>
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</pre>
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<p>
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then specialize <code class="computeroutput"><span class="identifier">common_type</span></code>
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@@ -463,16 +487,15 @@
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<span class="identifier">E2</span><span class="special">,</span> <span class="identifier">E3</span><span class="special">></span></code>
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and <code class="computeroutput"><span class="identifier">expected</span><span class="special"><</span><span class="identifier">T2</span><span class="special">,</span> <span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E4</span><span class="special">,</span>
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<span class="identifier">E5</span><span class="special">></span></code>
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is <code class="computeroutput"><span class="identifier">expected</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>,</span>
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<span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E2</span><span class="special">,</span> <span class="identifier">E3</span><span class="special">,</span> <span class="identifier">E4</span><span class="special">,</span>
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<span class="identifier">E5</span><span class="special">></span></code>.
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That is, the possible return values are combined into their common type,
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and we take the union of the set of error types.
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is <code class="computeroutput"><span class="identifier">expected</span><span class="special"><</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>,</span> <span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E2</span><span class="special">,</span>
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<span class="identifier">E3</span><span class="special">,</span> <span class="identifier">E4</span><span class="special">,</span> <span class="identifier">E5</span><span class="special">></span></code>. That is, the possible return values
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are combined into their common type, and we take the union of the set of
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error types.
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</p>
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<p>
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Therefore,
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">E1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">E2</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">common_expected</span> <span class="special">=</span> <span class="identifier">mp_rename</span><span class="special"><</span><span class="identifier">mp_push_front</span><span class="special"><</span><span class="identifier">mp_unique</span><span class="special"><</span><span class="identifier">mp_append</span><span class="special"><</span><span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E2</span><span class="special">>>,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>>,</span> <span class="identifier">expected</span><span class="special">>;</span>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">E1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">E2</span><span class="special">></span> <span class="keyword">using</span> <span class="identifier">common_expected</span> <span class="special">=</span> <span class="identifier">mp_rename</span><span class="special"><</span><span class="identifier">mp_push_front</span><span class="special"><</span><span class="identifier">mp_unique</span><span class="special"><</span><span class="identifier">mp_append</span><span class="special"><</span><span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E2</span><span class="special">>>,</span> <span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>>,</span> <span class="identifier">expected</span><span class="special">>;</span>
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<span class="keyword">namespace</span> <span class="identifier">std</span>
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<span class="special">{</span>
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@@ -491,7 +514,7 @@
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This makes our job easier. <code class="computeroutput"><span class="identifier">mp_unique</span><span class="special"><</span><span class="identifier">mp_append</span><span class="special"><</span><span class="identifier">E1</span><span class="special">,</span> <span class="identifier">E2</span><span class="special">>></span></code>
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gives us the concatenation of <code class="computeroutput"><span class="identifier">E1</span></code>
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and <code class="computeroutput"><span class="identifier">E2</span></code> with the duplicates
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removed; we then add <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span></code>
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removed; we then add <code class="computeroutput"><span class="identifier">common_type_t</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span></code>
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to the front via <code class="computeroutput"><span class="identifier">mp_push_front</span></code>;
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and finally, we <code class="computeroutput"><span class="identifier">mp_rename</span></code>
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the resultant <code class="computeroutput"><span class="identifier">mp_list</span></code> to
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@@ -2421,7 +2444,7 @@
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</div>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"><p><small>Last revised: May 23, 2017 at 17:21:43 GMT</small></p></td>
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<td align="left"><p><small>Last revised: May 23, 2017 at 17:37:57 GMT</small></p></td>
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<td align="right"><div class="copyright-footer"></div></td>
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</tr></table>
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<hr>
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