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<refnamediv>

<refname>bcsqrt</refname>

<refpurpose>任意精度数字的二次方根</refpurpose>

</refnamediv>

<refsect1 role="description">

&reftitle.description;

<methodsynopsis>

<type>string</type><methodname>bcsqrt</methodname>

<methodparam><type>string</type><parameter>num</parameter></methodparam>

<methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>scale</parameter><initializer>&null;</initializer></methodparam>

</methodsynopsis>

<simpara>

返回 <parameter>num</parameter> 的二次方根。

</simpara>

</refsect1>

<refsect1 role="parameters">

&reftitle.parameters;

<para>

<variablelist>

<varlistentry>

<term><parameter>num</parameter></term>

<listitem>

<para>

操作数，格式良好的 BCMath 数字字符串。

</para>

</listitem>

</varlistentry>

<xi:include xpointer="function.bcadd..parameters.scale" />

</variablelist>

</para>

</refsect1>

<refsect1 role="returnvalues">

&reftitle.returnvalues;

<para>

返回平方根，作为格式良好的 BCMath 数字字符串。

</para>

</refsect1>

<refsect1 role="errors">

&reftitle.errors;

<para>

此函数在以下情况下引发 <classname>ValueError</classname> 错误：

<simplelist>

<member><parameter>num</parameter> 不是格式良好的 BCMath 数字字符串</member>

<member><parameter>num</parameter> 小于 <literal>0</literal></member>

<member><parameter>scale</parameter> 超出有效范围</member>

</simplelist>

</para>

</refsect1>

<refsect1 role="changelog">

&reftitle.changelog;

<informaltable>

<tgroup cols="2">

<thead>

<row>

<entry>&Version;</entry>

<entry>&Description;</entry>

</row>

</thead>

<tbody>

<row>

<entry>8.0.0</entry>

<entry>

如果 <parameter>num</parameter> 不是格式良好的 BCMath 数字字符串，或小于 <literal>0</literal>，则会引发

<classname>ValueError</classname> 错误。之前，会引发 <constant>E_WARNING</constant> 错误。

</entry>

</row>

<row>

<entry>8.0.0</entry>

<entry>

现在，<parameter>scale</parameter> 的取值范围必须在 <literal>0</literal> 到 <literal>2147483647</literal> 之间；之前，负数的 scale 值会被静默处理为 <literal>0</literal>。

</entry>

</row>

<row>

<entry>8.0.0</entry>

<entry>

现在 <parameter>scale</parameter> 可以为 null。

</entry>

</row>

</tbody>

</tgroup>

</informaltable>

</refsect1>

<refsect1 role="examples">

&reftitle.examples;

<example>

<title><function>bcsqrt</function> 示例</title>

<programlisting role="php">

<![CDATA[

<?php

echo bcsqrt('2', 3); // 1.414

?>

]]>

</programlisting>

</example>

</refsect1>

<refsect1 role="seealso">

&reftitle.seealso;

<para>

<simplelist>

<member><function>bcpow</function></member>

<member><methodname>BcMath\Number::sqrt</methodname></member>

</simplelist>

</para>

</refsect1>

</refentry>

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