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2025年07月08日 15時33分39秒
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<div class="identifier-type">function template</div><div class="header"><numeric></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">transform_reduce</span><span class="cpp cpp17" title="C++17で追加">(C++17)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">);</span><span class="w"> </span><span class="c1">// (1) C++17</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="n">T</span>
<span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">);</span><span class="w"> </span><span class="c1">// (1) C++20</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation2</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation1</span><span class="w"> </span><span class="n">binary_op1</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation2</span><span class="w"> </span><span class="n">binary_op2</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2) C++17</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation2</span><span class="o">></span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="n">T</span>
<span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation1</span><span class="w"> </span><span class="n">binary_op1</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation2</span><span class="w"> </span><span class="n">binary_op2</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2) C++20</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">UnaryOperation</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation</span><span class="w"> </span><span class="n">binary_op</span><span class="p">,</span>
<span class="w"> </span><span class="n">UnaryOperation</span><span class="w"> </span><span class="n">unary_op</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3) C++17</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">InputIterator</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">UnaryOperation</span><span class="o">></span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="n">T</span>
<span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">InputIterator</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w"> </span><span class="n">InputIterator</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation</span><span class="w"> </span><span class="n">binary_op</span><span class="p">,</span>
<span class="w"> </span><span class="n">UnaryOperation</span><span class="w"> </span><span class="n">unary_op</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3) C++20</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">ForwardIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">ForwardIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="o">&&</span><span class="w"> </span><span class="n">exec</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">);</span><span class="w"> </span><span class="c1">// (4) C++17</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">ForwardIterator1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">ForwardIterator2</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation1</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation2</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="o">&&</span><span class="w"> </span><span class="n">exec</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator1</span><span class="w"> </span><span class="n">first1</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator1</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator2</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation1</span><span class="w"> </span><span class="n">binary_op1</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation2</span><span class="w"> </span><span class="n">binary_op2</span><span class="p">);</span><span class="w"> </span><span class="c1">// (5) C++17</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">ForwardIterator</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">BinaryOperation</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">UnaryOperation</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="o">&&</span><span class="w"> </span><span class="n">exec</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator</span><span class="w"> </span><span class="n">first</span><span class="p">,</span>
<span class="w"> </span><span class="n">ForwardIterator</span><span class="w"> </span><span class="n">last</span><span class="p">,</span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">init</span><span class="p">,</span>
<span class="w"> </span><span class="n">BinaryOperation</span><span class="w"> </span><span class="n">binary_op</span><span class="p">,</span>
<span class="w"> </span><span class="n">UnaryOperation</span><span class="w"> </span><span class="n">unary_op</span><span class="p">);</span><span class="w"> </span><span class="c1">// (6) C++17</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>transform_reduce()</code>は、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a>の要素を変換しながら集計する関数である。</p>
<p>(1), (2), (4), (5)は、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first1, last1)</code>の各要素を<code>x</code>、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first2, first2+(last1 - first1))</code>の各要素を<code>y</code>として、初期値(<code>init</code>)と<code>binary_op2(x, y)</code>した各要素を合算したリストの任意の組み合わせに、順不同で<code>binary_op1(binary_op1(a, b), binary_op1(c, d))</code>のように適用していき、集計値を計算する。</p>
<p>(3)と(6)は、初期値(<code>init</code>)と、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first, last)</code>の各要素に関数オブジェクト<code>unary_op</code>を適用して合算したリストの任意の組み合わせに、順不同で<code>binary_op(binary_op(a, b), binary_op(c, d))</code>のように適用していき、集計値を計算する。</p>
<ul>
<li>(1) : リスト集計の二項演算に<code>operator+</code>を使用し、2つの範囲の要素を掛け合わせる二項演算に<code>operator*</code>を使用する</li>
<li>(2) : リスト集計の二項演算に<code>binary_op1</code>を使用し、2つの範囲の要素を掛け合わせる二項演算に<code>binary_op2</code>を使用する</li>
<li>(3) : リスト集計の二項演算に<code>operator+</code>を使用し、各要素の変換に<code>unary_op</code>を使用する</li>
<li>(4) : (1)の並列アルゴリズム版。第1パラメータとして実行ポリシーをとる</li>
<li>(5) : (2)の並列アルゴリズム版。第1パラメータとして実行ポリシーをとる</li>
<li>(6) : (3)の並列アルゴリズム版。第1パラメータとして実行ポリシーをとる</li>
</ul>
<h2>要件</h2>
<ul>
<li>(1), (2), (4), (5) : 関数オブジェクト<code>binary_op1</code>と<code>binary_op2</code>の呼び出しは、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first1, last1]</code>と<code>[first2, first2 + (last1 - first1)]</code>の要素変更およびイテレータの無効化をしてはならない</li>
<li>(3), (6) : 関数オブジェクト<code>unary_op</code>と<code>binary_op</code>の呼び出しは、<a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first, last]</code>の要素変更およびイテレータの無効化をしてはならない</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Constraints。関数であればオーバーロード解決に参加するための条件、それ以外であれば受け付ける型の条件">テンプレートパラメータ制約</a></h2>
<ul>
<li>(1), (2), (3), (4), (5), (6) : 型<code>T</code>が<code><a href="../concepts/move_constructible.html">std::move_constructible</a></code>要件を満たすこと</li>
<li>(1), (2), (4), (5) : 以下の全ての演算結果の型が、型<code>T</code>に変換可能であること<ul>
<li><code>binary_op1(init, init)</code></li>
<li><code>binary_op1(init, binary_op2(*first1, *first2))</code></li>
<li><code>binary_op1(binary_op2(*first1, *first2), init)</code></li>
<li><code>binary_op1(binary_op2(*first1, *first2), binary_op2(*first1, *first2))</code></li>
</ul>
</li>
<li>(3), (6) : 以下の全ての演算結果の型が、型<code>T</code>に変換可能であること<ul>
<li><code>binary_op(init, init)</code></li>
<li><code>binary_op(init, unary_op(*first))</code></li>
<li><code>binary_op(unary_op(*first), init)</code></li>
<li><code>binary_op(unary_op(*first), unary_op(*first))</code></li>
</ul>
</li>
</ul>
<h2>効果</h2>
<ul>
<li>
<p>(1) : 以下と等価
<br />
<div class="codehilite"><pre><span></span><code><span class="k">return</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n">first1</span><span class="p">,</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span><span class="w"> </span><span class="n">init</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../functional/plus.html">plus</a></span><span class="o"><></span><span class="p">(),</span><span class="w"> </span><span class="n"><a href="../functional/multiplies.html">multiplies</a></span><span class="o"><></span><span class="p">);</span>
</code></pre></div>
</p>
</li>
<li>
<p>(2), (5) : <a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first1, last1)</code>と<code>[first2, first2+(last1 - first1))</code>について、リスト<code>[init, binary_op2(*first1, *first2), binary_op2(*(first1 + 1), *(first2 + 1)), binary_op2(*(first1 + 2), *(first2 + 2)), ...]</code>を任意の部分リストへ分割し、各部分リストの要素を順不同に<code>binary_op1(a, b)</code>を実行していき、それを実行していった結果同士も順不同に<code>binary_op1(sum1, sum2)</code>のように集計して返す</p>
</li>
<li>
<p>(3), (6) : <a class="cpprefjp-defined-word" data-desc="2つのイテレータで表現される半開区間を表す。C++20からイテレータと番兵で異なる型であっても指定可能になる">イテレータ範囲</a><code>[first, last)</code>について、リスト<code>[init, unary_op(*first), unary_op(*(first + 1)), unary_op(*(first + 2)), ... unary_op(*(first + (last - first - 1)))]</code>を任意の部分リストへ分割し、各部分リストの要素を順不同に<code>binary_op(a, b)</code>を実行していき、それを実行していった結果同士も順不同に<code>binary_op(sum1, sum2)</code>のように集計して返す</p>
</li>
<li>
<p>(4) : 以下と等価
<br />
<div class="codehilite"><pre><span></span><code><span class="k">return</span><span class="w"> </span><span class="n">transform_reduce</span><span class="p">(</span><span class="n"><a href="../utility/forward.html">std::forward</a></span><span class="o"><</span><span class="n"><a href="../execution/execution/execution_policy.html">ExecutionPolicy</a></span><span class="o">></span><span class="p">(</span><span class="n">exec</span><span class="p">),</span>
<span class="w"> </span><span class="n">first1</span><span class="p">,</span><span class="w"> </span><span class="n">last1</span><span class="p">,</span><span class="w"> </span><span class="n">first2</span><span class="p">,</span><span class="w"> </span><span class="n">init</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../functional/plus.html">plus</a></span><span class="o"><></span><span class="p">(),</span><span class="w"> </span><span class="n"><a href="../functional/multiplies.html">multiplies</a></span><span class="o"><></span><span class="p">());</span>
</code></pre></div>
</p>
</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Complexity。関数が使うアルゴリズムの空間計算量・時間計算量">計算量</a></h2>
<ul>
<li>(1), (2), (4), (5) : 関数オブジェクト<code>binary_op1</code>と<code>binary_op2</code>を、O(<code>last1 - first1</code>)回だけ適用する</li>
<li>(3), (6) : 関数オブジェクト<code>unary_op</code>と<code>binary_op</code>をO(<code>last - first</code>)回だけ適用する</li>
</ul>
<h2>備考</h2>
<ul>
<li>(3), (6) : 関数オブジェクト<code>unary_op</code>は初期値<code>init</code>に対しては適用しない</li>
</ul>
<h2>例</h2>
<p><div class="yata" id="60617e9712aef698b0faa3df428e6d24dea759ee"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../vector.html"><vector></a></span>
<span class="cp">#include <a href="../numeric.html"><numeric></a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../vector/vector.html">std::vector</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">v1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">};</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../vector/vector.html">std::vector</a></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">v2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">};</span>
<span class="w"> </span><span class="c1">// (1) : 2つのリストを集計する</span>
<span class="w"> </span><span class="c1">// sum1 = 1*2 + 2*3 + 3*4 + 4*5, 5*6</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sum1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::transform_reduce</span></span><span class="p">(</span><span class="n"><a href="../vector/vector/begin.html">v1.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../vector/vector/end.html">v1.end()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../vector/vector/begin.html">v2.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"sum1 : "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">sum1</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// (2) : 2つのリストを集計する。</span>
<span class="w"> </span><span class="c1">// リストを集計する2項演算と、2つのリストの要素を掛け合わせる2項演算を指定する</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sum2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::transform_reduce</span></span><span class="p">(</span><span class="n"><a href="../vector/vector/begin.html">v1.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../vector/vector/end.html">v1.end()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../vector/vector/begin.html">v2.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w"> </span><span class="p">},</span><span class="w"> </span><span class="c1">// 集計関数</span>
<span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">b</span><span class="p">;</span><span class="w"> </span><span class="p">});</span><span class="w"> </span><span class="c1">// 2つの要素を合成する関数</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"sum2 : "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">sum2</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// (3) : リストの各要素を変換しながら集計する</span>
<span class="w"> </span><span class="c1">// 1*2 + 2*2 + 3*2 + 4*2 + 5*2</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">sum3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::transform_reduce</span></span><span class="p">(</span><span class="n"><a href="../vector/vector/begin.html">v1.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../vector/vector/end.html">v1.end()</a></span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">acc</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">acc</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="p">},</span><span class="w"> </span><span class="c1">// 集計関数</span>
<span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span><span class="w"> </span><span class="p">});</span><span class="w"> </span><span class="c1">// 変換関数</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"sum3 : "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">sum3</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code>sum1 : 70
sum2 : 70
sum3 : 30
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++17</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: 5.0.0 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>:</li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: ??</li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0024r2.html" target="_blank">P0024R2 The Parallelism TS Should be Standardized</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0452r1.html" target="_blank">P0452R1 Unifying <code><numeric></code> Parallel Algorithms</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0467r2.html" target="_blank">P0467R2 Iterator Concerns for Parallel Algorithms</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0574r1.html" target="_blank">P0574R1: Algorithm Complexity Constraints and Parallel Overloads</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0623r0.html" target="_blank">P0623R0 Final C++17 Parallel Algorithms Fixes</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1645r1.html" target="_blank">P1645R1 <code>constexpr</code> for <code><numeric></code> algorithms</a><ul>
<li>C++20で、並列バージョン以外の数値計算アルゴリズムが<code>constexpr</code>対応した</li>
</ul>
</li>
</ul></div>
</div>
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