Index: doc/src/sgml/typeconv.sgml
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RCS file: /cvsroot/pgsql-server/doc/src/sgml/typeconv.sgml,v
retrieving revision 1.27
diff -c -c -r1.27 typeconv.sgml
*** doc/src/sgml/typeconv.sgml	13 Mar 2003 01:30:29 -0000	1.27
--- doc/src/sgml/typeconv.sgml	19 Mar 2003 21:17:32 -0000
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  </para>
  </example>
  
- <example>
- <title>Absolute-Value and Factorial Operator Type Resolution</title>
- 
- <para>
- The <productname>PostgreSQL</productname> operator catalog has several
- entries for the prefix operator <literal>@</>, all of which implement
- absolute-value operations for various numeric data types.  One of these
- entries is for type <type>float8</type>, which is the preferred type in
- the numeric category.  Therefore, <productname>PostgreSQL</productname>
- will use that entry when faced with a non-numeric input:
- <screen>
- SELECT @ '-4.5' AS "abs";
-  abs
- -----
-  4.5
- (1 row)
- </screen>
- Here the system has performed an implicit conversion from <type>text</type> to <type>float8</type>
- before applying the chosen operator.  We can verify that <type>float8</type> and
- not some other type was used:
- <screen>
- SELECT @ '-4.5e500' AS "abs";
- 
- ERROR:  Input '-4.5e500' is out of range for float8
- </screen>
- </para>
- 
- <para>
- On the other hand, the postfix operator <literal>!</> (factorial)
- is defined only for integer data types, not for <type>float8</type>.  So, if we
- try a similar case with <literal>!</>, we get:
- <screen>
- SELECT '20' ! AS "factorial";
- 
- ERROR:  Unable to identify a postfix operator '!' for type 'text'
-         You may need to add parentheses or an explicit cast
- </screen>
- This happens because the system can't decide which of the several
- possible <literal>!</> operators should be preferred.  We can help
- it out with an explicit cast:
- <screen>
- SELECT CAST('20' AS int8) ! AS "factorial";
- 
-       factorial
- ---------------------
-  2432902008176640000
- (1 row)
- </screen>
- </para>
- </example>
- 
  </sect1>
  
  <sect1 id="typeconv-func">
--- 403,408 ----