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Even better example for operator precedence mis-parsing.

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Peter Eisentraut 2001-02-25 16:05:21 +00:00
parent 2a398726e7
commit 60774e8210
1 changed files with 4 additions and 4 deletions
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8
doc/src/sgml/syntax.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.40 2001/02/24 18:09:51 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.41 2001/02/25 16:05:21 petere Exp $
-->
<chapter id="sql-syntax">
@ -905,17 +905,17 @@ sqrt(2)
you will sometimes need to add parentheses when using combinations
of binary and unary operators. For instance
<programlisting>
SELECT 5 ! + 6;
SELECT 5 ! - 6;
</programlisting>
will be parsed as
<programlisting>
SELECT 5 ! (+ 6);
SELECT 5 ! (- 6);
</programlisting>
because the parser has no idea -- until it is too late -- that
<token>!</token> is defined as a postfix operator, not an infix one.
To get the desired behavior in this case, you must write
<programlisting>
SELECT (5 !) + 6;
SELECT (5 !) - 6;
</programlisting>
This is the price one pays for extensibility.
</para>