Doc: improve documentation about exponentiation operator.

Now that we're not having to wedge this into the straitjacket of
the old operator table format, we can add another example to
clarify the point about left-to-right associativity.

Per suggestion from mdione at grulic.org.ar.

https://postgr.es/m/162661954599.693.13700316547731859171@wrigleys.postgresql.org

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index e833be8f96b797be3e3b3de53d9dfefcdb5ca5e2..f62c33e5c71a01364756c12003aac2b65abf3769 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -988,16 +988,23 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
         <returnvalue>double precision</returnvalue>
        </para>
        <para>
-        Exponentiation (unlike typical mathematical practice, multiple uses of
-        <literal>^</literal> will associate left to right)
+        Exponentiation
        </para>
        <para>
         <literal>2 ^ 3</literal>
         <returnvalue>8</returnvalue>
        </para>
+       <para>
+        Unlike typical mathematical practice, multiple uses of
+        <literal>^</literal> will associate left to right by default:
+       </para>
        <para>
         <literal>2 ^ 3 ^ 3</literal>
         <returnvalue>512</returnvalue>
+       </para>
+       <para>
+        <literal>2 ^ (3 ^ 3)</literal>
+        <returnvalue>134217728</returnvalue>
        </para></entry>
       </row>