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152 lines
7.1 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>指数表达式</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.pow" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">pow</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">pow</span> — <span class="dc-title">指数表达式</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.pow-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>pow</strong></span>
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( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span> <code class="parameter">$base</code></span>
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, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span> <code class="parameter">$exp</code></span>
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) : <span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span></div>
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<p class="para rdfs-comment">
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返回 <code class="parameter">base</code> 的
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<code class="parameter">exp</code> 次方的幂。如果可能，本函数会返回
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<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>。
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.pow-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">base</code></dt>
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<dd>
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<p class="para">
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The base to use
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</p>
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</dd>
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<dt>
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<code class="parameter">exp</code></dt>
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<dd>
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<p class="para">
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指数
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</p>
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</dd>
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</dl>
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</p>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.pow-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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<code class="parameter">base</code> 的
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<code class="parameter">exp</code> 次方的幂。
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If both arguments are non-negative integers and the result can be represented
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as an integer, the result will be returned with <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> type,
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otherwise it will be returned as a <span class="type"><a href="language.types.float.html" class="type float">float</a></span>.
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</p>
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</div>
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<div class="refsect1 changelog" id="refsect1-function.pow-changelog">
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<h3 class="title">更新日志</h3>
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<p class="para">
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<table class="doctable informaltable">
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<thead>
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<tr>
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<th>版本</th>
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<th>说明</th>
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</tr>
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</thead>
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<tbody class="tbody">
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<tr>
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<td>4.2.0</td>
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<td>
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如果不能计算幂，将发出一条警告，<span class="function"><strong>pow()</strong></span> 将返回 <strong><code>FALSE</code></strong>。<span class="function"><strong>pow()</strong></span> 开始不产生任何的警告。
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</td>
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</tr>
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<tr>
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<td>4.0.6</td>
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<td>
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如果可能函数现在会返回 <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> 的结果，之前
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总是返回 <span class="type"><a href="language.types.float.html" class="type float">float</a></span>，For older
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versions, you may receive a bogus result for complex numbers.
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</td>
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</tr>
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</tbody>
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</table>
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.pow-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-4139">
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<p><strong>Example #1 <span class="function"><strong>pow()</strong></span> 的一些例子</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /><br />var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #0000BB">8</span><span style="color: #007700">)); </span><span style="color: #FF8000">// int(256)<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">20</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1<br /><br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">5.5</span><span style="color: #007700">); </span><span style="color: #FF8000">// PHP >4.0.6 NAN<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #0000BB">5.5</span><span style="color: #007700">); </span><span style="color: #FF8000">// PHP <=4.0.6 1.#IND<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 notes" id="refsect1-function.pow-notes">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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本函数会转换所有输入为数字，即使是非标量值，会导致怪异的（<em>weird</em>）结果。
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.pow-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="exp.html" class="function" rel="rdfs-seeAlso">exp()</a> - 计算 e 的指数</span></li>
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<li class="member"><span class="function"><a href="sqrt.html" class="function" rel="rdfs-seeAlso">sqrt()</a> - 平方根</span></li>
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<li class="member"><span class="function"><a href="bcpow.html" class="function" rel="rdfs-seeAlso">bcpow()</a> - 任意精度数字的乘方</span></li>
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<li class="member"><span class="function"><a href="gmp_pow.html" class="function" rel="rdfs-seeAlso">gmp_pow()</a> - Raise number into power</span></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |