php-doc-en/reference/math/functions/expm1.xml
2020-12-26 19:26:31 +00:00

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XML

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.expm1">
<refnamediv>
<refname>expm1</refname>
<refpurpose>
Returns exp(number) - 1, computed in a way that is accurate even
when the value of number is close to zero
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>float</type><methodname>expm1</methodname>
<methodparam><type>float</type><parameter>num</parameter></methodparam>
</methodsynopsis>
<para>
<function>expm1</function> returns the equivalent to
'exp(<parameter>num</parameter>) - 1' computed in a way that is
accurate even if the value of <parameter>num</parameter> is near zero,
a case where 'exp (<parameter>num</parameter>) - 1' would be
inaccurate due to subtraction of two numbers that are nearly equal.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>num</parameter></term>
<listitem>
<para>
The argument to process
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
'e' to the power of <parameter>num</parameter> minus one
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>log1p</function></member>
<member><function>exp</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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