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Add support for hyperbolic functions, as well as log10().

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The SQL:2016 standard adds support for the hyperbolic functions
sinh(), cosh(), and tanh().  POSIX has long required libm to
provide those functions as well as their inverses asinh(),
acosh(), atanh().  Hence, let's just expose the libm functions
to the SQL level.  As with the trig functions, we only implement
versions for float8, not numeric.

For the moment, we'll assume that all platforms actually do have
these functions; if experience teaches otherwise, some autoconf
effort may be needed.

SQL:2016 also adds support for base-10 logarithm, but with the
function name log10(), whereas the name we've long used is log().
Add aliases named log10() for the float8 and numeric versions.

Lætitia Avrot

Discussion: https://postgr.es/m/CAB_COdguG22LO=rnxDQ2DW1uzv8aQoUzyDQNJjrR4k00XSgm5w@mail.gmail.com
This commit is contained in:
Tom Lane
2019-03-12 15:55:09 -04:00
parent 3aa0395d4e
commit f1d85aa98e
6 changed files with 333 additions and 6 deletions
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107
doc/src/sgml/func.sgml
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@ -896,6 +896,19 @@
<entry><literal>2</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>log10</primary>
</indexterm>
<literal><function>log10(<type>dp</type> or <type>numeric</type>)</function></literal>
</entry>
<entry>(same as input)</entry>
<entry>base 10 logarithm</entry>
<entry><literal>log10(100.0)</literal></entry>
<entry><literal>2</literal></entry>
</row>
<row>
<entry><literal><function>log(<parameter>b</parameter> <type>numeric</type>,
<parameter>x</parameter> <type>numeric</type>)</function></literal></entry>
@ -1147,8 +1160,8 @@
</para>
<para>
Finally, <xref linkend="functions-math-trig-table"/> shows the
available trigonometric functions. All trigonometric functions
<xref linkend="functions-math-trig-table"/> shows the
available trigonometric functions. All these functions
take arguments and return values of type <type>double
precision</type>. Each of the trigonometric functions comes in
two variants, one that measures angles in radians and one that
@ -1311,6 +1324,96 @@
</para>
</note>
<para>
<xref linkend="functions-math-hyp-table"/> shows the
available hyperbolic functions. All these functions
take arguments and return values of type <type>double
precision</type>.
</para>
<table id="functions-math-hyp-table">
<title>Hyperbolic Functions</title>
<tgroup cols="4">
<thead>
<row>
<entry>Function</entry>
<entry>Description</entry>
<entry>Example</entry>
<entry>Result</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<indexterm>
<primary>sinh</primary>
</indexterm>
<literal><function>sinh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>hyperbolic sine</entry>
<entry><literal>sinh(0)</literal></entry>
<entry><literal>0</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>cosh</primary>
</indexterm>
<literal><function>cosh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>hyperbolic cosine</entry>
<entry><literal>cosh(0)</literal></entry>
<entry><literal>1</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>tanh</primary>
</indexterm>
<literal><function>tanh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>hyperbolic tangent</entry>
<entry><literal>tanh(0)</literal></entry>
<entry><literal>0</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>asinh</primary>
</indexterm>
<literal><function>asinh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>inverse hyperbolic sine</entry>
<entry><literal>asinh(0)</literal></entry>
<entry><literal>0</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>acosh</primary>
</indexterm>
<literal><function>acosh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>inverse hyperbolic cosine</entry>
<entry><literal>acosh(1)</literal></entry>
<entry><literal>0</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>atanh</primary>
</indexterm>
<literal><function>atanh(<replaceable>x</replaceable>)</function></literal>
</entry>
<entry>inverse hyperbolic tangent</entry>
<entry><literal>atanh(0)</literal></entry>
<entry><literal>0</literal></entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>